Language：English   Publishing type：Research paper (scientific journal)   Publisher：Physical Society of Japan  

DOI： 10.7566/jpsj.92.094703

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Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

Materials containing Dirac fermions (DFs) have been actively researched because they often alter electrical and magnetic properties in an unprecedented manner. Although many studies have suggested the transformation between standard fermions (SFs) and DFs, the non-availability of appropriate samples has prevented the observation of the transformation process. We observed the interconversion process of DFs and SFs using organic charge-transfer (CT) salts. The samples are unique in that the constituents (the donor D and acceptor A species) are particularly close to each other in energy, leading to the temperature- and D-A-combination-sensitive CT interactions in the solid states. The three-dimensional weak D–A CT interactions in low-symmetry crystals induced the continuous reshaping of flat-bottomed bands into Dirac cones with decreasing temperature; this is a characteristic shape of bands that converts the behavior of SFs into that of DFs. Based on the first-principles band structures supported by the observed electronic properties, round-apex-Dirac-cone-like features appear and disappear with temperature variation. These band-structure snapshots are expected to add further detailed understanding to the related research fields.

DOI： 10.3390/magnetochemistry9060153

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Publishing type：Research paper (scientific journal)   Publisher：Physical Society of Japan  

DOI： 10.7566/jpsj.92.024701

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：World Scientific Pub Co Pte Ltd  

Bicyclo[2.2.2]octadiene(BCOD)-fused 5,15-diazaporphyrins were synthesized via a metal-template aza-annulation of dipyrrin-metal complexes as a soluble precursor of tetrabenzodiazaporphyrin. 10-Azacorrole copper complex with a meso-imine bridge was serendipitously obtained via the same reaction using dimethylBCOD-fused dipyrrin-copper complex.

DOI： 10.1142/s1088424623500074

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Physical Society of Japan  

Theoretical and experimental studies have supported that the electronic structure of α-(BEDT-TTF)2I3 under pressure is described by two-dimensional Dirac fermions. When the interlayer tunneling is coherent, the electronic structure of the system becomes three-dimensional, and we expect the peak structure to appear in the interlayer resistivity under magnetic fields. We theoretically and experimentally show that the peak appears in the interlayer resistivity at low temperatures and high magnetic fields. From the experiment, we estimate that the magnitude of the interlayer tunneling is t1 ∼ 1 meV. Our result opens the door to investigating the three-dimensional electronic structure of α-(BEDT-TTF)2I3

DOI： 10.7566/jpsj.92.013702

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Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

Original analysis methods of the electron spin resonance revealed that nearly three-dimensional Dirac fermions coexistent with standard fermions in an organic charge-transfer complex with each temperature-dependence and rotation symmetry.

DOI： 10.1039/d3ma00619k

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Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

Molecular and charge arrangements in the solid state were controlled by a new building block: a triad molecule.

DOI： 10.1039/d3cc03198e

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1246/bcsj.20220281

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

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Publishing type：Research paper (scientific journal)   Publisher：Physical Society of Japan  

DOI： 10.7566/jpsj.91.034707

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

Topological materials with Dirac electron systems have been extensively studied. Organic crystalline materials form a unique group of such compounds with well-defined crystal structures. While most organic compounds require high pressures to exhibit Dirac-cone-type band structures, the title compound, α-STF2I3, has garnered increasing interest due to its Dirac-cone-type band structure under ambient pressure. Various experiments have been conducted under ambient pressure; their results can be compared with those of theoretical calculations to obtain insights into Dirac electron systems. However, structural disorder peculiar to the STF molecules in the solid-state has prevented any type of theoretical calculation of the states. In this study, we report a new method for calculating intermolecular interactions in disordered systems based on the extended Hückel approximation. This method enables band calculations, suggesting that this material is a rare example of a system close to merging. The obtained band structure indicates that the characteristic disorder in the STF solids distributed electrons equally on the sulphur and selenium atoms as if they belong to an imaginary element between sulphur and selenium and are arranged without disorder.

DOI： 10.3390/cryst12030346

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Language：English   Publishing type：Research paper (scientific journal)  

We investigated the interlayer magnetoresistance in an organic massless Dirac electron system α-(BEDT-TTF)2I3 under pressure. We experimentally demonstrate that the width of the zero mode owing to carrier scattering is much narrower than that of the other Landau levels.

DOI： 10.7566/JPSJ.91.045001

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

We have found that the electrical properties of an organic charge transfer salt are qualitatively affected by slight differences in the conformation of one of the ethylene groups, which is not involved in the conduction pathways.

DOI： 10.1039/d1ma00933h

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

We have found a general relationship between the dimensions of the sample structures and the physical/chemical properties.

DOI： 10.1039/d1cp04709d

PubMed

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Physical Society of Japan  

DOI： 10.7566/jpsj.90.114704

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Authorship：Lead author,　Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

This short review article provides the reader with a summary of the history of organic conductors. To retain a neutral and objective point of view regarding the history, background, novelty, and details of each research subject within this field, a thousand references have been cited with full titles and arranged in chronological order. Among the research conducted over ~70 years, topics from the last two decades are discussed in more detail than the rest. Unlike other papers in this issue, this review will help readers to understand the origin of each topic within the field of organic conductors and how they have evolved. Due to the advancements achieved over these 70 years, the field is nearing new horizons. As history is often a reflection of the future, this review is expected to show the future directions of this research field.

DOI： 10.3390/cryst11070838

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Applied Physics  

DOI： 10.7566/jpsj.90.063708

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Publishing type：Research paper (scientific journal)   Publisher：Physical Society of Japan  

In-plane magnetoresistance for organic massless Dirac electron system (OMDES) α-(BEDT-TTF)2I3and θ-(BEDTTTF) 2I3in addition to possible candidates of the OMDES α-(BETS)2I3and α-(BEDT-STF)2I3, was investigated under hydrostatic pressure. We have found the universal behavior of the in-plane magnetoresistance under a low magnetic field perpendicular to two-dimensional plane. As for α-(BEDT-TTF)2I3, the universality was examined with the parameters of temperature, magnetic field and its direction. We suggest that the universal magnetoresistance behavior is found even for the gapped state of α-(BEDT-TTF)2I3under intermediate pressure, when the thermal energy exceeds the gap.

DOI： 10.7566/jpsj.89.113703

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

The physical properties of molecular crystals are governed by the frontier orbitals of molecules. A molecular orbital, which is formed by superposing the atomic orbitals of constituent elements, has complicated degrees of freedom in the crystal because of the influence of electron correlation and crystal field. Therefore, in general, it is difficult to experimentally observe the whole picture of a frontier orbital. Here, we introduce a new method called “core differential Fourier synthesis” (CDFS) using synchrotron X-ray diffraction to observe the valence electron density in materials. By observing the valence electrons occupied in molecular orbitals, the orbital state can be directly determined in a real space. In this study, we applied the CDFS method to molecular materials such as diamond, C60 fullerene, (MV)I2, and (TMTTF)2X. Our results not only demonstrate the typical orbital states in some materials, but also provide a new method for studying intramolecular degrees of freedom.

DOI： 10.3390/cryst10110998

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Authorship：Lead author,　Last author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

The smart utilization of photons is paid global attention from the viewpoint of renewable energy and information technology. However, it is still impossible to store photons as batteries and condensers do for electrons. All the present technologies utilize (the energy of) photons in situ, such as solar panels, or in spontaneous relaxation processes, such as photoluminescence. If we can store the energy of photons over an arbitrary period and utilize them on demand, not only we will make an innovative progress in energy management, but we will also be able to replace a part of electrons by photons in the information technology for more efficient performance. In this article, we review a prototype of such a material including the current status of related research as well as where we are heading for.

DOI： 10.3390/inorganics8100053

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Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PHYSICAL SOC JAPAN  

In this study, to investigate the electronic state of organic molecular crystal kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]I (kappa-1), polarized pump probe spectroscopy was conducted. From the observation of photoinduced carrier relaxation dynamics, we found that the carrier dynamics in kappa-I are qualitatively different from those in other kappa-type salts and inhomogeneous electronic states are realized in the single crystal. As temperature decreases, the transient polarization anisotropy along the c axis associated with a charge order develops below T-MI = 40K, which is consistent with the metal insulator transition observed in the resistivity measurement. Moreover, we found the position where the transient polarization anisotropy is enhanced along the 1/2 (a + c) direction. Remarkably, this signal shows no clear changes at T-MI = 40 K; instead, it shows an anomalous increase in the signal amplitude at T similar to 8 K. A possible origin of this anomaly is the locally induced superconducting state.

DOI： 10.7566/JPSJ.89.064712

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Physical Society of Japan  

DOI： 10.7566/jpsj.89.034709

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1039/C9TC00491B

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

<p>Gold(<sc>iii</sc>) atoms reversibly deviate from the molecular plane on receiving thermal and photon energy.</p>

DOI： 10.1039/c9dt02377a

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Language：English   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

Spin liquid (SL) systems have been the subject of much attention recently, as they have been theoretically predicted to not freeze, even at 0 K. Despite extensive searches being made for such a system, only a few candidates have been found. All of these candidates share geometrical frustrations that are based on triangular lattices. We applied vibrational spectroscopy to one of the candidates of a molecule-based SL system, and we compared its results against three antiferromagnetic compounds and four charge-ordered compounds. All of their structural motifs belong to triangular lattices. The C=C stretching modes in the SL state indicated that there were charge and lattice fluctuations. These fluctuations were suppressed but non-negligible in the AF compounds. This finding is potentially significant, as it indicates that a hidden lattice and charge fluctuation are the driving force of a geometrical frustration, which eventually leads to a SL state.

DOI： 10.1038/s41598-017-13118-4

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

This study concerns development of a non-destructive method to control conduction and magnetism of molecular solids such as single crystals of charge-transfer complexes. The method is named "optical doping", where appropriate irradiation is utilized under ambient conditions. Owing to this feature, it can be applied to a wide range of substances while measuring the properties during the control. In addition, the method adds unique conduction and magnetic properties to common insulators. Unlike other doping methods, optical doping only affects the properties and/or structures of the irradiated part of a sample while leaving the rest of the sample unchanged. There are two patterns in the optical doping. Irreversible optical doping produces junction-structures on the single molecular crystals, which exhibit characteristic behavior of semiconductor devices such as diodes and varistors. Reversible optical doping produces "giant photoconductors" and "photomagnetic conductors" by realizing unprecedented metallic photoconduction. In the latter case, localized spins are also excited to produce a Kondo system, where carriers and localized spins interact with each other. Not only the control of conduction and magnetism, the optical doping has realized the observation of physical properties in molecular crystals hardly observed under any thermodynamic condition.

DOI： 10.1246/bcsj.20160295

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

DOI： 10.11316/jpsgaiyo.71.1.0_1858

CiNii Books

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Language：Japanese   Publisher：The Physical Society of Japan  

DOI： 10.11316/jpsgaiyo.71.2.0_1600

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

DOI： 10.11316/jpsgaiyo.70.2.0_1504

CiNii Books

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

DOI： 10.11316/jpsgaiyo.70.2.0_1633

CiNii Books

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

[Cu(dmit)(2)](2-) formally consists of a magnetic Cu2+ ion (S = 1/2) and closed-shell pi-conjugated dmit(2-) ligands. However, it has been determined by electron spin resonance and molecular orbital calculations that the majority (91-100%) of the spin delocalizes over the ligands in the ground state, while the spin significantly (40-90%) localizes on Cu under UV irradiation. Considering the results of X-ray structural analyses under UV irradiation, the spin distribution varies depending on the wavelengths irradiated and retaining the square-planar coordination geometries.

DOI： 10.1246/cl.140318

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

The simple molecular salt NMQ[Ni(dmit)(2)] (NMQ = N-methylquinolinium, dmit = 1,3-dithiol-2-thione-4,5-dithiolate) functions as a diamagnetic insulator with an activation energy E-a(dark) of 0.20 eV. However, at 300 K, it exhibits ca. 40 times higher conductivity (sigma(UV)) under UV irradiation [(375 +/- 5) nm, 15.7 mW cm(-2)] than it does under dark conditions (sigma(dark)). The ratio sigma(UV)/sigma(dark) rapidly increases with decreasing temperature and reaches ca. 880 at 200 K. From the temperature dependence of sigma(UV), the activation energy under irradiation E-a(UV) is 0.12 eV. These observations cannot be explained as the result of sample heating during UV irradiation. Rather, the X-ray photoelectron spectra of the sulfur and nickel atoms, the calculated band structure, and the UV/Vis spectra of the salt can all be explained consistently as follows: charge transfer between the Ni(dmit)(2) moieties upon exposure to 375 nm UV light induces melting of the charge-ordered state and produces the unusually large photoconductivity of NMQ[Ni(dmit)(2)].

DOI： 10.1002/ejic.201402035

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

beta-DiCC[Ni(dmit)(2)] (dmit: 1,3-dithiole-2-thione-4,5-dithiolato and DiCC: 3,3'-dihexyloxacarbocyanine) is a charge-transfer salt with redox activity. When voltages are applied, it brings about a reversible, hysteretic, solid-state-electrolytic reaction exhibiting a capacitor-like electric response. Based on the electron spin resonance spectra, the resistivity behavior, and the tight-binding band calculation, it is indicated that one can finely and reversibly control the redox equilibrium between DiCC(+) and [Ni(dmit)(2)](-) molecules by applying voltages.

DOI： 10.1246/cl.140309

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

It is well-known that cooperative properties such as magnetic ordering can depend on the samples' dimensions (Ds) in a qualitative way. However, there have been no samples with well-defined non-integer Ds. The dimension of a given sample has been always discussed on the anisotropy of the electronic/crystal/magnetic structures, which has no definition suitable for quantitative discussion on dimensions vs. properties. On the other hand a particular type of porous samples, i.e. fractal bodies, can have well-defined non-integer Ds dependent exclusively on the geometrical feature of structures, and physical properties of such materials remains unexplored. This paper reports on magnetic ordering in samples covering 2.5 &lt;= D &lt;= 3, in addition to a way of precise control of the fractal dimensions of given samples simply by wax (alkylketene dimer). The results show that the magnetic ordering temperatures, i.e. Neel temperatures (T(N)s), of CoO depend on D, and rapidly enhance immediately below D = 3. This means that one can control or enhance the critical temperature simply by tuning D with keeping the remaining magnetic properties unchanged.

DOI： 10.1140/epjb/e2013-40353-3

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PHYSICAL SOC JAPAN  

The magnetization and transport properties of iron-phthalocyanine molecular conductors are investigated under pulsed high magnetic fields up to 55 T. The metamagnetic transition is observed at approximately 14 T, where conductivity is enhanced. Below this transition, the tan delta (= epsilon ''/epsilon') in the dielectric constants shows a monotonic decrease as the magnetic field strength increases, indicating that the magnetic field stabilizes the charge order. On the verge of this transition, the dielectric constants show a hysteresis below the weak-ferromagnetic transition temperature (6 K), suggesting that the pi-electron charge order contributes to the weak ferromagnetism.

DOI： 10.7566/JPSJ.82.094713

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Language：English   Publisher：The Physical Society of Japan  

We have measured the magnetic torque of TPP[Fe(Pc)Br<inf>2</inf>]<inf>2</inf>and TPP[Fe(Pc)Cl<inf>2</inf>]<inf>2</inf>to clarify their magnetic state, comparing our results with those of formerly performed experiments on TPP[Fe(Pc)CN<inf>2</inf>]<inf>2</inf>. The conductors in this family exhibit giant negative magnetoresistance. We employed the cantilever magnetometry technique with our newly developed calibration method to obtain absolute values of the torque (J/rad Fe mol), enabling the comparison between experimental and calculated results. With decreasing temperature, the antiferromagnetic ordering of the \pi electron is found to occur at {\sim}13 K, and then the antiferromagnetic short-range ordering of the d electron follows at {\sim}8 K in these two salts. Our anisotropic one-dimensional Heisenberg model can explain 1) the susceptibility data quantitatively, 2) the torque curves quantitatively, which were obtained when the magnetic field was rotated in the ac-plane, and 3) the behavior of the d electron in the torque curves qualitatively, which were obtained by rotating the field in the ab-plane. By combining our model with the antiferromagnetic model for the \pi electron, the experimental torque data on TPP[Fe(Pc)Br<inf>2</inf>]<inf>2</inf>and TPP[Fe(Pc)Cl<inf>2</inf>]<inf>2</inf>are satisfactorily described. In addition, we could also successfully obtain the anisotropy energy in the antiferromagnetic state.

DOI： 10.7566/JPSJ.82.034719

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Language：English   Publishing type：Research paper (scientific journal)  

We have measured the magnetic torque of TPP[Fe(Pc)Br2] 2 and TPP[Fe(Pc)Cl2]2 to clarify their magnetic state, comparing our results with those of formerly performed experiments on TPP[Fe(Pc)CN2]2. The conductors in this family exhibit giant negative magnetoresistance. We employed the cantilever magnetometry technique with our newly developed calibration method to obtain absolute values of the torque (J/rad Fe mol), enabling the comparison between experimental and calculated results. With decreasing temperature, the antiferromagnetic ordering of the π electron is found to occur at ̃13 K, and then the antiferromagnetic short-range ordering of the d electron follows at ̃8K in these two salts. Our anisotropic one-dimensional Heisenberg model can explain 1) the susceptibility data quantitatively, 2) the torque curves quantitatively, which were obtained when the magnetic field was rotated in the ac-plane, and 3) the behavior of the d electron in the torque curves qualitatively, which were obtained by rotating the field in the ab-plane. By combining our model with the antiferromagnetic model for the π electron, the experimental torque data on TPP[Fe(Pc)Br2]2 and TPP[Fe(Pc)Cl2]2 are satisfactorily described. In addition, we could also successfully obtain the anisotropy energy in the antiferromagnetic state. © 2013 The Physical Society of Japan.

DOI： 10.7566/JPSJ.82.034719

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DOI： 10.7566/JPSJ.82.034719

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer New York LLC  

The temperature-dependent time-resolved reflectance spectra of the organic superconductors (OSs) κ- and λ- (BETS)2MCl4 (M = Fe, Ga) and κ-(ET)2Cu[N(CN)2]Br are reported. The π electrons of the organic molecules (BETS or ET) are responsible for the electrical conduction in these salts, while only the Fe-containing salts have localized spins on the d electrons in the Fe atoms (S = 5/2) with π–d interaction. Analysis of the spectra provided the relaxation time τ of the carriers, as well as information concerning the number of carriers at the Fermi energy N(EF). The carrier dynamics were classified in terms of high-TC and low-TC OSs. In these salts, the results indicate that (1) the electron-phonon interaction is important in the occurrence and stability of the superconducting phase, and (2) electron correlation can be related to the enhancement of TC.

DOI： 10.1007/s10948-012-2007-1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

An organic insulating crystal reversibly becomes a magnetic conductor under UV irradiation. The rapid and qualitative change in the physical properties is wavelength selective and explained by charge transfer between donor and photochemically active acceptor molecules. The photochemical redox reaction in the crystal produces a partially filled band and localized spins simultaneously.

DOI： 10.1002/adma.201203153

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

UV irradiation reversibly switches a new insulating and nonmagnetic molecular crystal, BPY[Ni(dmit)(2)](2) (BPY = N,N'-ethylene-2,2'-bipyridinium; Ni(dmit)(2) = bis(1,3-dithiole-2-thione-4,5-dithiolato)nickelate(III)), into a magnetic conductor. This is possible because the bipyridyl derivative cations (BPY2+) trigger a photochemical redox reaction in the crystal to produce a change of similar to 10% in the filling of the Ni(dmit)(2) valence band, leaving localized spins on the BPY themselves. In the dark, almost all of the BPY molecules are closed shell cations, and most of the Ni(dmit)(2). radical anions form spin singlet pairs; thus, this material is a diamagnetic semiconductor. Under UV irradiation, a photocurrent is observed, which enhances the conductivity by 1 order of magnitude Electron-spin resonance. measurements indicate that the 'UV:. irradiation reversibly generates. carriers and localized spins on the Ni(dmit)(2). and the BPY, respectively: This high photoconductivity can be explained by charge transfer (CT) transitions between Ni(dmit)(2) and BPY in the UV region. In other words, the photoconduction and "photomagnetism" can be described as reversible optical control of the electronic states between an ionic salt (BPY2+/[Ni(dmit)(2)](-), nonmagnetic insulator) and a CT complex (BPY2(1-delta)+/[Ni(dmit)(2)]((1-delta)-) (delta approximate to 0.1), magnetic conductor) in the solid state.

DOI： 10.1021/ja306260b

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

Electrolysis of Na and K salts of the anion dicyano(phthalocyaninato) cobalt(III) (Co(Pc)(CN)(2)) in ethanol yields one-dimensional partially oxidized salts of A[Co(Pc)(CN)(2)](2)center dot 4(EtOH) (A = Na and K). The cationic component is the supramolecular cation [A(EtOH)(4)](+), which forms hydrogen bonds with the CN ligands of the Co(Pc)(CN)(2) units. The crystal shows metallic conductivity, in contrast to the thermally activated conductivity observed in the isomorphous tetraphenylphosphonium (TPP) salt of TPP[Co(Pc)(CN)(2)](2). Since the pi-pi interactions in these isomorphous crystals are nearly the same, the distinctive behavior of the Na and K salts may be attributed to the difference in the degree of charge disproportionation in these crystals.

DOI： 10.3390/cryst2030946

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

The electrical conductivity of the organic Mott insulator ET-F(2)TCNQ (ET = bis(ethylenedithio) tetrathiafulvalene, F(2)TCNQ = 2,5-difluoro-7,7,8,8-tetracyanoquinodimethane) crystal was found to be enhanced by conjugation with a tetrathiafulvalene (TTF) single crystal on its surface; surface sheet resistance decreased from 5 x 10(5) to 2 x 10(3) Omega/sq. The mechanism of this decrement was investigated through optical and atomic force microscopy measurements at the interface. When TTF was conjugated to the ET-F(2)TCNQ crystal, electron injection from TTF and complex formation between TTF and F(2)TCNQ occurred. Neutral ET molecules were consequently generated at the interface, and this charge doping broke the Mott insulating state. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4750066]

DOI： 10.1063/1.4750066

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Language：English   Publishing type：Research paper (international conference proceedings)  

The dicyano(phthalocyaninato)iron molecular conductor shows the Giant Magnetoresistance (GMR) effect. In order to investigate the effect of the molecular structure and charge on the X-ray absorption in the Fe(Pc)(CN)2 molecule, we measured the Fe K-edge X-ray Absorption Near Edge Structure (XANES) spectra in the TPP[Fe(Pc)L 2] 2 (L=CN, Br, and Cl), DMDP[Fe(Pc)(CN) 2], and [(n-C 2H 2) 4N][Fe(Pc)(CN) 2]. In 7134-7152 eV, we found the clear difference in the XANES spectra between these Fe(Pc)(CN) 2compounds. Our multiple scattering calculations indicate that the local structure of the iron and CN ligand, which tends to be changed by the nominal charge in the Pc ring, causes the spectral change.© 2012 The Surface Science Society of Japan.

DOI： 10.1380/ejssnt.2012.92

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

Electrolysis of ET in a mixed solvent of methanol/CHCl3 with bromide yielded (ET)(3)(Br-3)(5), in which an unusually high formal charge of ET5/3+ is achieved. ET forms a two-dimensional conducting sheet incorporating Br-3(-). Despite the high formal charge of the ET cations, the strong electrostatic attractions between the ET cations and Br-3(-) support aggregation of the ET cations, allowing sufficient pi-pi overlap for delocalization of the pi-electrons. The crystal shows stable metallic behavior down to low temperatures, being consistent with the metallic band structure with two-dimensional Fermi surfaces and Pauli-like paramagnetism down to low temperatures. The lack of any indication of instability in the metallic phase due to correlation effects is considered to result from an ionic-crystal-like structure, in which the lattice is more resistant toward lattice deformation and/or shrinkage than in typical partially oxidized salts with low formal charges.

DOI： 10.1246/bcsj.20110253

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The interface between tetrathiafulvalene (TTF) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) crystals was prepared by treating a TCNQ single crystal surface with TTF powder. Optical measurements and atomic force microscopy (AFM) observation of the interface indicated that not only are TTF-TCNQ nanocrystals formed at the interface, but also direct charge injection from TTF powder to the TCNQ single crystal surface may be responsible for the high conductivity of the interface.

DOI： 10.1021/jp2074368

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PHYSICAL SOC JAPAN  

The charge distribution in the surface BEDT-TTF layer of the alpha-(BEDT-TTF)(2)I-3 crystal with the charge disproportionation state at room temperature was studied in detail by a scanning tunneling microscope (STM), where BEDT-TTF (abbreviated as ET) is bis(ethylenedithio) tetrathiafulvalene. The obtained molecular charge distribution in the surface ET layer suggests that the electronic states of the surface ET layer at room temperature is the charge-ordered state, stable below 135K in bulk crystals, rather than the charge disproportionation state above 135 K. The most probable mechanism underlying this remarkable finding is the particular freedom to the surface ET layer. The missing of the I-3 layer partially removes the structural constraint of the steric interaction between the thermally vibrating ethylene groups and the neighboring two I-3 layers. This mechanism would have something in common with the layered ET complexes.

DOI： 10.1143/JPSJ.81.014707

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Understanding how electrons behave, i.e., carrier dynamics, in superconductors is indispensable for understanding the mechanism of superconductivity. Recently we have reported the carrier dynamics of kappa- and lambda-(BETS)(2)MCl4 (BETS = bis(ethylenedithio)tetraselenafulvalene, M = Ga, Fe) based on ultrafast spectroscopy, but the interpretation of the results remains an open question. In this paper we interpreted the results with the aid of newly measured magnetic susceptibility, X-ray single crystal structural analysis, and band calculation. Observation of coherent phonons only in the lambda-type salts indicated that e-ph interaction should be characteristically strong in the A-type salts. By comparison of the observed carrier dynamics with a two-temperature model, the temperature-dependence of carrier dynamics is consistently explained by the different strengths of the e-ph interaction between the lambda- and the kappa-type salts. The difference in strength of the e-ph interactions is related to their crystal structures. In conclusion, their carrier dynamics is consistently interpreted and classified by their crystal structures.

DOI： 10.1021/jp210966u

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Time-resolved photoresponses in resistance have been measured following the nanosecond laser pulse excitation for the quasi-two-dimensional organic superconductors of hydrogenated and deuterated beta-(BEDT-TTF)(2)I-3 [BEDT-TTF = bis-(ethylenedithio)tetrathiafulvalene], which show two different superconducting states with high-T-c and low-T-c at temperatures near the critical temperatures. A transient increase of the resistance is induced by photoirradiation at all the temperatures, but a marked temperature dependence of the decay time is observed at temperatures close to the high-T-c phase transition temperature; the decay rate becomes faster and then becomes constant in both compounds, as the temperature decreases across the high-T-c phase transition temperature. The temperature dependence of the photoresponse intensity is different from the one expected from the bolometric effects, indicating the presence of the nonbolometric photoresponse. A possible mechanism explaining the photoresponse of the conductivity is discussed, based on the isotope effect on the photoresponse. A comparison is also made between beta-(BEDT-TTF)(2)I-3 and kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]Br for the transient photoresponse in resistance at temperatures across the metal-superconductor phase transition temperature.

DOI： 10.1021/jp2088912

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We investigate the relaxation dynamics of nonequilibrium carriers in organic conductors kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]X (X = Br and Cl) using ultrafast time-resolved optical spectroscopy. The dynamics for both salts show similar temperature dependences, which is well characterized by the carrier relaxation across the pseudogap (PG) of the magnitude Delta(PG) approximate to 16 meV for Br salt and 7.0 meV for Cl salt. On the other hand, only the Br salt shows an abrupt increase of the decay time at low temperature, indicating an additional decay component associated with the superconducting (SC) gap below T-c. The fluence dependent dynamics at low temperature evidences the superposition of the SC component onto the PG component. These results indicate a metallic-insulating phase separation in the Br salt triggered by photoexcited nonequilibrium carriers.

DOI： 10.1103/PhysRevLett.107.227002

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We have recently found that organic conductors Ag(DR)(2) (DR = 2,5-disubsituted-N,N&apos;-dicyanoquinone amine; substituent (R) = CH(3), Cl, Br, I) irreversibly vary their electrical and magnetic properties by UV irradiation. By selecting the irradiation conditions (wavelengths, temperature, atmosphere, duration), one can accurately control the physical properties from metallic to insulating behavior while retaining their crystal structures. In order to clarify the mechanism of the conductivity change in the case of R = Cl, Br, and I, structure analysis of the irradiated crystals has been carried out. Transmittance electron microscopy and X-ray single crystal structure analysis clarified that the Ag(DCl)(2) crystals after 72 h irradiation (375 nm) contained single crystals of nearly three-dimensionally ordered AgCl (0.9 in mole fraction) with varying dimensions (similar to 1-50 nm). Owing to such a unique hybrid crystal structure, a highly nonlinear current-voltage characteristic unlike any existing electronic devices is observed on irradiated single Ag(DCl)(2) crystals.

DOI： 10.1021/cg101295p

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We performed static susceptibility and Se-77 NMR measurements on alpha-(BETS)(2)I-3 and alpha-(BEDT-STF)(2)I-3 which are analogues of the "zero gap" system, alpha-(BEDT-TTF)(2)I-3 to systematically compare the electronic properties of the alpha-type I-3 systems, where BETS, BEDT-STF, and BEDT-TTF are bis(ethylendithio) tetraselenafulvalene, bis(ethylendithio) dithiadiselenafulvalene, and bis(ethylendithio) tetrathiafulvalene, respectively. From the analysis of the NMR lineshape for a polycrystalline sample at high temperatures, which are explained as an admixture of several powder patterns, we found that the local spin susceptibility is not uniform but at least one of the molecular sites has very small susceptibility. It was confirmed from single crystal data that there are three kinds of molecules with different local susceptibilities in a unit cell. The analysis of the angular dependence on a single crystal clarified that the relative magnitude of the local susceptibilities of A, B, and C molecules, chi(loc)(A), chi(loc)(B), and chi(loc)(C), are similar to those of the BEDT-TTF salt; chi(loc)(C) &gt; chi(loc)(A) &gt; chi(loc)(B). On the contrary, the temperature dependence of spin susceptibility and relaxation rate suggested a gap opening well above the metal-insulator transition, whereas no indication of symmetry breaking of the lattice was detected.

DOI： 10.1143/JPSJ.80.014715

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The structural and electrical properties of a metal-halide cubic perovskite, CH3NH3SnI3, have been examined. The band structure, obtained using first-principles calculation, reveals a well-defined band gap at the Fermi level. However, the temperature dependence of the single-crystal electrical conductivity shows metallic behavior down to low temperatures. The temperature dependence of the thermoelectric power is also metallic over the whole temperature range, and the large positive value indicates that charge transport occurs with a low concentration of hole carriers. The metallic properties of this as-grown crystal are thus suggested to result from spontaneous hole-doping in the crystallization process, rather than the semi-metal electronic structure. The present study shows that artificial hole doping indeed enhances the conductivity.

DOI： 10.1039/c0dt01601b

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The partially-oxidized TPP[M(Pc)L-2](2) molecular conductors exhibit variable electronic and magnetic transport bulk materials properties due to central metal and axial ligand molecular modifications. The controllable electrical conductivity and giant negative magnetoresistance can be mainly attributable to the varying ligand field energy and physical bulkiness of the axial ligands which cause modulation in the intra-molecular pi-d (Pc-M) and inter-molecular pi-pi (Pc-Pc) interactions in the TPP[M(Pc)L-2](2) system, respectively. Characterization of the electronic conduction band utilizing one-dimensional (1-D) tight-binding approximation from infrared reflectance and thermoelectric power profile reveal consistent band widths of 0.43 eV-0.62 eV for the Co series (L = Br &lt; Cl &lt; CN) and 0.44-0.56 eV for the Fe series (L = Br &lt; Cl &lt; CN). The fixed band width suggests that stable electron conduction bands (transport pathway) can be constructed which can withstand the molecular pi-d interaction modifications that severely alter the bulk electronic and magnetic materials properties of the TPP[M(Pc)L-2](2) molecular conductors.

DOI： 10.1039/c0dt01054e

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Magnetic torque measurements of TPP[Fe(Pc)Br-2](2) are reported The torque curves for the magnetic field rotated within the ac plane exhibit a two-fold symmetry The temperature dependences of the torque amplitudes divided by the square of the field strength (tau(phi-45)/B-2) exhibit a drastic field dependence below 12K This field dependence is attributable to the fluctuation in the spontaneous magnetization that appears below 4 5 K The torque curves for the field rotated within the ab plane exhibit four-fold symmetry The curves are sinusoidal above 18K and exhibit saw-toothed shapes below similar to 12 K and complicated shapes below 8K. The complicated shapes suggest that both d-electrons and it-electrons form a magnetic order below 8K (C) 2009 Elsevier B V All rights reserved

DOI： 10.1016/j.physb.2009.11.023

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Unprecedented memory effect of photoinduced switching of the electrical conductivity in alpha-(BEDT-TTF)(2)I-3 controlled by the temporal width of square-wave pulsed voltages was reported where BEDT-TTF represents bis(ethylenedithio)tetrathiafulvalene [9] [limori et al 2009] Here further study has been done in order to examine whether the memory effect can be controlled by changing the height of the pulsed voltage Threshold values in the voltage height for the occurrence of the memory effect are characterized as a function of the width of pulsed voltages The relation between the threshold height and the pulse width can be altered by a load resistance connected to the sample in series in a measurement circuit It is also argued that time profiles of current observed in response to the application of pulsed voltages are inconsistent with a scenario in which the memory effect is ascribed to a temperature rise of the sample caused by photoirradiation and the successive application of pulsed voltages i e the memory effect is not a thermal effect (C) 2009 Elsevier B V All rights reserved

DOI： 10.1016/j.physb.2009.10.031

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Photoirradiation effect on the electrical conductivity has been examined for an organic superconductor kappa-(BEDT-TrF)(2)Cu[N(CN)(2)]Br where BEDT-TTF represents bis(ethylenedithio)tetrathiafulvalene based on the time-resolved resistance measurements Visible laser pulses with a wavelength of 532 nm were irradiated on the crystal surface and the transient voltage signals induced by photoirradiation in the current-biased sample were monitored to obtain the transient time profile of the resistance The Increase of the resistance upon photoirradiation is observed with a slow decay lifetime of the order of millisecond both in the metallic phase and in the superconducting phase The time profiles are remarkably different from each other and a slow rise was observed only in the time profiles of the superconducting phase (C) 2009 Elsevier B V All rights reserved

DOI： 10.1016/j.physb.2009.11.042

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In order to compare the carrier dynamics in lambda-(BETS)(2)MCl4 (M=Ga Fe) and kappa-(ET)(2)X (X=Cu(NCS)(2) Cu[N(CN)(2)]Br Cu[N(CN)(2)]Cl) their polarized reflectance spectra were measured by a pump-probe method Polarization-dependences were compared among the different materials at varying temperatures The result indicated that each salt had anisotropy in the conduction planes corresponding to its crystallographic axes at all the temperatures of measurements (C) 2009 Elsevier B V All rights reserved

DOI： 10.1016/j.physb.2009.12.049

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Photoinduced change in the electrical conductivity of a single crystal of kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]Br (kappa-Br) has been examined at various temperatures in the vicinity of the metal superconductor phase-transition temperature (T-c) with a nanosecond visible laser pulse. The transient change of the electric potential difference was measured following photoirradiation, and the time profile of the electrical conductivity was obtained in the current-biased sample. Upon photoirradiation, the bulk resistance increases at all the temperatures under the present study. However, the decay profile shows a marked temperature dependence, and a prolongation of the decay time is observed at temperatures just below T-c. The relaxation times below and above T-c are different from each other, and unconventional asymmetry of the critical slowing down about T-c is found. The presence of a nonthermal (nonbolometric) photoirradiation effect is confirmed in the superconducting phase of kappa-Br based on the analysis of the temperature dependence of the photoresponse in the conductivity.

DOI： 10.1021/jp912204n

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In order to compare the carrier dynamics and reveal the origin of differences in their electrical behaviour, time-resolved reflectivity changes were measured on single crystals of the title compounds. The observed relaxation behaviour explained well their electrical behaviour, and indicated that different conduction mechanisms dominated kappa-and lambda-type BETS salts, irrespective of local spins, at about 8-100 K; the electrical behaviour of the kappa-type salts is governed by relaxation times of carriers and/or density of states at the Fermi levels, while that of the lambda-type salts is dominated by the latter.

DOI： 10.1088/0953-8984/22/18/185701

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Mellitate is a unique anion that can form hydrogen-bonding anionic networks. In this study, crystal structures of the salts with quaternary ammonium and phosphonium cations that bear no hydrogen-bonding functional groups are investigated. When the number of deprotonation (n) from the parent mellitic acid is one, two kinds of networks, a two-dimensional sheet and a three-dimensional network containing helical chains, have been obtained. Both networks involve a common network motif, and this variation arises from the difference in the connection sequence of the motif. When n = 2, a rhombic motif that frequently occurs in the salts with proton-donating cations is also found to form. However, the vacant proton accepting sites of the anions are occupied by water molecules, and a sheet-like network with corner-sharing connection of the rhombic motifs occurs. For the salt of n = 3, a triangular motif that has commonly been found in the other mellitate salts of n = 3 with proton-donating cations is also involved in the network. Because the charge density in the simple two-dimensional sheet composed solely of the triangular motif is rather high, the network is divided into one-dimensional belts.

DOI： 10.1246/bcsj.20090323

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Magnetoresistance (MR) and magnetic torque measurements are performed for a magnetic organic conductor TPP[Fe(Pc)(CN) 2] 2. The results suggest that the large negative MR is associated with a magnetic transition. This magnetic transition is considered as a metamagnetic transition of the localized Fe moments, and the MR effect is qualitatively explained by an analogy with the double exchange interaction system. © 2010 Springer Science+Business Media, LLC.

DOI： 10.1007/s10909-009-0110-x

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A peak appearing at the L-2,L-3 X-ray absorption edge often provides the number of empty d states of the X-ray absorbing atoms. Ag+ compounds have a d(10) state (no d empty states) but Show a small peak at the edge. In this research, we systematically studied the edge peak of Ag+ compounds to Understand its origin oil the basis of the molecular Orbital picture and to obtain a relation of the edge peak intensity to chemical and physical quantities. The edge peak call be formally assigned to the transition from 2p to 5s enhanced by the s-d hybridization. The peak intensity has a negative correlation with I coordination charge but has a positive correlation with the strength of the covalent bond, which is in the reverse order to the other d(n) (n &lt; 10) elements.

DOI： 10.1021/jp907669s

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Electrochemical oxidation of [M(III)(Pc)(CN)(2)](-) (M = Co and Fe, Pc = phthalocyaninato) and peri-xanthenoxanthene (PXX) in acetonitrile yields partially oxidized salts of [PXX](2)[M(Pc)(CN)(2)]center dot CH(3)CN. In the crystal, the Pc ring is formally oxidized by 0.5 e and forms a two-dimensional double-sheet layer. These crystals show semiconducting behavior with small activation energy under ambient pressure, but show metallic behavior under high pressures. When M - Co, the metallic behavior is maintained down to 5 K. On the other hand, in the pi-d system with M = Fe, the metallic behavior is disrupted by a steep increase in the resistivity at low temperatures. In this high resistivity state, negative differential resistance appears in the measurements of current-voltage characteristics, suggesting the development of charge disproportionation due to the pi-d interaction. The magnetic susceptibility for M = Fe reflects anisotropic molecular magnetism of the Fe(Pc)(CN)(2) unit, and shows an anomaly due to antiferromagnetic interaction between the Fe d-spins. The increase in the resistivity at low temperature under high pressures is suppressed by the application of a magnetic field. The magnitude of the negative magnetoresistance effect is extremely large; -99.8% was recorded at a field of 15 T at 3 K under 12 kbar.

DOI： 10.1039/c0jm00161a

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Electrochemical oxidation of bis(ethylenedithio)terathiafulvalene (ET) with mellitic acid and pyridine in methanol produces a partially oxidized salt of [ET](3)[C(6)(COO)(6)H(4)(2-)](2)[C(5)H(5)NH(+)](2)center dot CH(3)OH center dot 2H(2)O (1). In the crystal of 1, mellitate anions form a two-dimensional hydrogen-bonding double-sheet layer with pyridinium, methanol, and water. ET molecules are packed between the layers, forming a two-dimensional conducting sheet. The ET arrangement in the sheet resembles that in alpha-ET(2)I(3), which has it metal-to-insulator transition. The transition into insulating states is completely suppressed in 1 due to the close packing of ET molecules in the supramolecular mellitate network.

DOI： 10.1021/cg900655v

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The Ag(DMe-DCNQI)(2) (DMe-DCNQI = 2,5-dimethyl-N,N&apos;-dicyanoquinonediimine, or DM) charge-transfer salt is a promising material for production by photolithography as it displays a unique photoinduced change in conduction. Photoproducts (beta 1 and gamma) of Ag(DM)(2) were investigated using the X-ray absorption fine structure (XAFS) technique in order to understand the origin of their conduction properties. In contrast to the metallic conduction exhibited by a pristine sample (alpha), beta 1 is a semiconductor, whereas gamma is an insulator, even though the original Ag(DM)(2) composition is maintained in both the beta 1 and the gamma forms. A redox mechanism has been postulated to explain the photoinduced change in conduction. However, measurement of the Ag L-3-edge XANES (X-ray absorption near-edge structure) did not provide any evidence of electron transfer from the DM radical anion to the Ag cation in the beta 1 and gamma products. Ag K-edge extended X-ray absorption fine structure (EXAFS) data demonstrated that beta 1 is a mixture of the original pristine alpha phase and a newly found alpha&apos; phase, which has a shorter bond distance between the Ag cations and the N atoms of DM molecules. The conduction electrons remain in the DM column of alpha and alpha&apos;, but the domain boundaries between alpha and alpha&apos; present an activation barrier for the conduction electrons to cross these boundaries, which provides a rationale for the semiconductive behavior of beta 1. The Ag K-edge EXAFS results showed that the gamma photoproduct has a different local structure from alpha, with a shorter distance and smaller coordination number of the Ag-N bond. The DM radical anions in the gamma compound form covalent bonds between themselves, resulting in a loss of the columnar structure. The complex local structure around Ag cations explains the insulating behavior of the gamma compound.

DOI： 10.1021/jp907024p

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The charge transport properties of a partially oxidized salt composed of Co(Pc)(CN)(2) units with a typical one-dimensional electronic system have been suggested to be determined by charge disproportionation. The current-voltage (I-V) characteristics show nonlinear behavior at low temperature, which is suppressed by applying pressure. The observed nonlinearity is considered to result from the electric-field-induced delocalization of carriers in the charge disproportionation state. In the isomorphous magnetic Fe(Pc)(CN)(2) system, the nonlinear behavior is observed at higher temperatures, suggesting that charge disproportionation is more developed in a system with local moments. The threshold voltage of negative differential resistance decreases when an external magnetic field is applied, confirming that the localization of charge carriers is released by magnetic field application.

DOI： 10.1143/JPSJ.78.104709

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Purity effects oil the temperature dependence of electrical resistivity in TPP[Co(Pc)(CN)(2)](2) with a typical one-dimensional metallic electronic system have been examined. In this system. no dependence on the impurity content has been observed, suggesting that the apparent thermally activated behavior is dominated by charge disproportionation.

DOI： 10.1246/bcsj.82.692

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Electrical conductivity switching is induced by photoirradiation in single crystals of alpha-(BEDT-TTF)(2)I(3) below 135 K. Photoirradiated crystals show differential negative resistance (DNR), and bistability is observed in the electrical conductivity as a function of applied voltage. The threshold in voltage, which induces the DNR, increases as the temperature decreases. A hysteresis loop appears in the current versus light intensity characteristic curve, and the feature of the hysteresis loop depends on the pulse width of the applied voltage. The switching to a high conductivity state is initially triggered by the laser light irradiation. The conductivity switching can be repeatedly recovered only by applying the pulsed voltages without further photoirradiation even after the cur-rent was reduced to zero, indicating a memory effect in the photoinduced conductivity switching. When pulsed voltages having smaller width and/or height than the corresponding threshold values are applied to the crystal, the field-induced recovery to the high-conductivity state due to the memory effect fades out. The thresholds in width and height of the pulsed voltage for the memory effect can be controlled by the photoirradiation light intensity. These results show that the electrical conductivity can be controlled by the width and height of the pulsed voltage as well as the light intensity without a change in temperature or pressure.

DOI： 10.1021/jp810351c

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A series of one-dimensional conductors, TPP[Fe-III(Pc)L-2](2) with L CN, Cl, and Br, have been prepared. These compounds show giant negative magnetoresistance due to the interaction between conduction pi-electrons and localized Fe-centered d-spins, but the magnitude is found to vary based on the axial ligand, suggesting that the strength of the pi-d interactions is sensitively influenced by the axial substituent. The magnetic susceptibility also shows the difference in the magnetic interactions by the axial substituent. The ab initio calculation of the isolated molecules has revealed that the Jahn-Teller effect in this system induces splitting of d(xz) and d(yz) orbitals, and that the energy shift of the d-orbital accommodating an unpaired electron is varied by the axial substituent. The axial-ligand dependence of the intramolecular pi-d interaction is found to correlate with the magnitude of the magnetoresistance.

DOI： 10.1039/b814609h

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Transient photoresponses of the electrical conductivity in single crystals of an organic conductor alpha-(BEDT-TTF)(2)I-3 are studied in the charge-ordered insulating phase. Electrical conductivity switching is observed in the presence of pulsed voltages and synchronous irradiation of nanosecond laser pulse. Current in the photoirradiated crystal as a function of applied voltages shows a bistability in a certain range of voltage. For the initial triggering of the conductivity switching, not only pulsed voltages but also photoirradiation is necessary. A high conductivity state produced by the switching can be repeatedly recovered by applying the pulsed voltages without further photoirradiation even after the current has been reduced to zero. This observation indicates a memory effect of the photoinduced conductivity switching. The appearance of the memory effect depends on the temporal width of the pulsed voltages, which are applied at a rate of approximately 8 Hz. In the measurement using short pulse widths, the memory effect is not observed. This controllability of the memory effect with the pulse width is related to the bistability of the current with respect to the photoirradiation intensity. The shape of the hysteresis loop appearing in the current versus photoirradiation intensity curve can be varied by changing the pulse width.

DOI： 10.1088/1742-6596/148/1/012009

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Magnetoresistance and magnetic torque measurements of one-dimensional pi-d organic conductor TPP[Fe(Pc)(CN)(2)](2) are performed in the temperature range of 30-1.5 K. The resistance shows semiconducting behavior in the whole temperature range, suggesting a charge ordered state. Quite large negative magnetoresistance is observed at low temperatures, which is associated with the change of the magnetic torque. These results show that the charge gap steeply decreases at about 14.5 T, where some magnetic transition of Fe 3d spins occurs. This is clear evidence that the pi electron transport is strongly correlated with the local spins via the strong pi-d interaction. Possible theoretical models, double-exchange interaction and pi-d spin-singlet models are discussed.

DOI： 10.1088/1742-6596/150/2/022040

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The K-type organic superconductors have unique physical properties, many of which are yet to be understood. Most of their physical properties are closely related to carrier dynamics, which can be directly observed by ultrafast optical measurements in their nonequilibrium states. Time-resolved temperature-dependent reflectivity changes were measured on single crystals of an isostructural pair of organic charge transfer salts kappa-(ET)(2)Cu[N(CN)(2)]X, which are ambient- (X = Br) or high-pressure (X = Cl) superconductors. The latter compound in its ground state is a Mott insulator under ambient pressure. The obtained temperature dependences of relaxation times for both salts indicated the existence of an intermediate electronic state between those of metals and insulators at all measurement temperatures. Such an unusual electronic state coexisted with the superconducting and Mott insulating states in X = Br and X = Cl, respectively. In addition, the results for X = Br revealed the formation of a temperature-dependent well-defined gap in the superconducting transition, while those for X = Cl suggested that the Mott transition in this salt does not depend on electron-phonon interactions, consistent with the theory that the Mott transition should originate from electron correlation.

DOI： 10.1143/JPSJ.77.064709

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By maintaining alpha-Ag(DM)(2) (DM = C10H8N4) around room temperature (RT) (&lt;&lt; 155 degrees C) during ultraviolet-visible (UV-vis) irradiation, a series of photochemical products named beta was obtained. The solid beta was comprised of structurally different compounds. All of the solid beta phases share the original chemical formula of Ag(DM)(2) and exhibit semiconducting behaviour, yet they differ from each other in their XRD patterns. They are divided into two phases: beta 1 and beta 2. Compared with the XRD pattern of the alpha phase, the beta 1 phase exhibited XRD peaks at the same 2 theta-angles but with different relative intensities, while the beta 2 phase exhibited totally different XRD patterns from those of the alpha or beta 1 phases. The actual composition of a particular solid of 'beta' phase is dependent upon irradiation time, and can be controlled continuously. Around RT, the alpha phase exhibits metallic conductivity, while the beta 1 and beta 2 phases are suggested to be semiconductors. As a result, one can continuously and finely control the electrical resistivity of Ag(DM)(2) by UV irradiation to modify it into a mixture of alpha, beta 1 and/or beta 2 phases.

DOI： 10.1088/0957-4484/18/42/424008

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UV-vis light converts A-(DM)(2) (DM = 2,5-dimethyl-N,N'-dicyanoquionediimine; DMe-DCNQI) to several solids with metallic, semiconducting, or insulating conductivities depending on the irradiation conditions. Ag valence state in each photochemical product was determined by Ag L-3-edge XANES. The XANES result requires the correction of the redox mechanism to explain the photoinduced conductivity change of Ag(DM)(2) photoproducts.

DOI： 10.1246/cl.2007.1008

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

A charge-transfer complex of 2,5-dimethyl-N,N'-dicyanoquinonediimine (DM) with silver (crystalline Ag(DM)(2), defined as a) is irreversibly transformed by UV-vis illumination. Depending on the illumination conditions, three new types of solids (defined as gamma, delta, and epsilon) with different structural and physical properties are obtained and examined by a variety of analytical techniques, including solid-state, high-resolution, cross-polarization magic angle spinning (CP-MAS) (CNMR)-C-13, elemental analysis (EA), mass spectrometry (MS), X-ray absorption fine structure (XAFS), and powder X-ray diffraction (XRD). The CP-MAS, EA, MS, and XAFS results indicate that compound gamma is a glass state of Ag(DM)(2). The transformation from crystalline (a) to amorphous (gamma) solid Ag(DM)(2) is an irreversible exothermic glass transition (glass-transition temperature 155.2 degrees C; Delta H=-1.26.8 kJ mol(-1)), which implies that the glass form is thermodynamically more stable than the crystalline form. Compound delta (Ag(DM)(1.5)) consists of silver nanoparticles (diameter (7 +/- 2) nm) dispersed in a glassy matrix of neutral DM molecules, The =N-CN-Ag coordination bonds of the a form are not maintained in the delta form. Decomposition of a by intense illumination results in a white solid (epsilon), identified as being composed of silver nanoparticles (diameter (60 +/- 10) nm). Physical and spectroscopic (XAFS) measurements, together with XRD analysis, indicate that the silver nanoparticles in both delta and epsilon are crystalline with lattice parameters similar to bulk silver; however, the magnetic susceptibilities differ from bulk silver.

DOI： 10.1002/adfm.200600583

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Photoirradiation effects on conductivity in the organic salt alpha-(BEDT-TTF)(2)I-3 at temperatures close to the metal-insulator (M-I) phase boundary are investigated using time-resolved measurements of photocurrent. The transient photocurrent at 115 K shows a remarkable persistence at the metallic conductivity and a nonlinear dependence on the light intensity, probably originating from the photoinduced M-I phase conversion in the presence of electric fields.

DOI： 10.1246/cl.2007.536

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Pyromellitate is known to form hydrogen-bonding anionic networks when the number of deprotonation from pyromellitic acid is one or two. This unique anion has been utilized for the construction of the pi-radical cationic salts of the tetrathiafulvalene (TTF) derivatives. In the crystals of three kinds of the TTF salts and the tetramethyltetraselenafulvalene salt, pyromellitate was found to form two-dimensional sheets. The anions in the two TTF salts were connected by rhombic-type inter-anionic connection, which is a typical inter-anionic connection pattern for pyromellitate. The TTF derivatives were all in a 7 pi-radical mono-cationic state and dimerized in a space dictated by the anionic networks. The extra space in the crystals was filled with crystal solvents. On the other hand, in the crystals of the ethylenedithia-tetrathiafulvalene salts, pyromellitate formed only intra-molecular hydrogen bonds. The anion was thus isolated in these crystals.

DOI： 10.1246/bcsj.80.476

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

We report that the photoinduced high conductivity (HC) state in the organic charge-transfer salt alpha-(BEDT-TTF)(2)I-3, which is initially triggered by a pulsed voltage and synchronous photoirradiation, can be repeatedly recovered without further photoirradiation by application of a pulsed voltage even after the current has been reduced to zero. The recovery to the HC state can be controlled by adjusting the pulse width and/or amplitude. By proper selection of pulsed voltage parameters, the switching can be made reversible or irreversible. Hysteresis loops in the current-voltage and current-irradiation intensity curves of the circuit demonstrate a memory effect with potential application in unconventional photoswitching operations. The characteristic of the hysteresis loop and current bistability can be flexibly varied by changing the width of the applied pulsed voltage.

DOI： 10.1021/ja068791d

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Language：Japanese   Publishing type：Research paper (other academic)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

Electrochemical oxidation of ET with Br- in methanol/ CHCl3 yields a metallic crystalline product, (ET)(3)(Br-3)(5), in which the bromine chemical species is all Br-3(-) and the formal charge of ET becomes an unusually high value (5/3+).

DOI： 10.1246/cl.2007.74

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PHYSICAL SOC JAPAN  

We investigated the ground state of a highly one-dimensional conductor, TPP[Co(Pc)(CN)(2)](2) (TPP tetraphenylphosphonium and Pc = phthalocyanine), by the measurement of the X-ray diffraction, electron spin resonance, nuclear quadrupole resonance, and magnetoresistance. An increase of the magnetic fluctuations was observed below 20 K, where no structural deformation was detected. In the Co-59 nuclear quadrupole resonance, we found an asymmetric broadening of the spectra owing to the intrinsic inhomogeneity of the molecular charge. We propose that the ground state is characterized by a weak charge disproportionation with antiferromagnetic fluctuations due to the high one dimensionality. A large magnetoresistance was observed under a high magnetic field. Spin effects are dominant at low fields. The anisotropic magnetoresistance suggests a change in the ground-state nature above 10 T.

DOI： 10.1143/JPSJ.75.104713

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

The one-pot syntheses of partially oxidized cobalt(III) phthalocyanine salts with axial halides, as well as a shorter route (single-step) for the axial dicyano counterpart are reported. The method utilizes an electrolytic reaction, and appears to be solvent dependent. Overlap integral calculations and electrical transport measurements indicate axial ligand effects on the molecular stacking of the cobalt phthalocyanine.

DOI： 10.1246/cl.2006.602

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The C-4h isomer of the 1,2- Nc ( 1,2- naphthalocyaninato) ligand has been efficiently isolated as a hydrated magnesium complex by the fractional crystallization from the benzene/ acetone solution after treating the crude mixture of the four isomers ( C-4h, C-s, C-2v, D-2h) with benzene. The C-4h symmetry has been confirmed by X- ray structure analysis. The central metal ion has been demetalated and subsequently converted to the Li-2 complex followed by conversion to the cobalt( II) complex. Electrochemical oxidation of the Co-III( 1,2- Nc)( CN)(2) anion prepared from the cobalt( II) complex with TPP ( tetraphenylphosphonium) has yielded a partially oxidized salt, TPP[ Co-III( 1,2- Nc- C (4h))( CN) (2)] (2). The crystal comprises slipped stacked Co-III( 1,2- Nc- C (4)h)( CN)(2) one- dimensional chains and one- dimensional arrays of TPPs. The conductivity at room temperature is 0.1 S cm(-1), and the temperature dependence is semiconducting with a small activation energy of about 0.05 eV. The positive temperature- independent value of about 60 mu V deg(-1) observed in the thermoelectric power measurements suggests that the salt is in the correlated hopping regime.

DOI： 10.1021/ic0520622

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PHYSICAL SOC JAPAN  

Materials containing Fe(Pc)(CN)(2) dicyano(phthalocyaninato)iron molecules show a giant negative magnetoresistance from the interaction between the conduction and the local moment. Under a magnetic field, the resistance becomes two orders of magnitude smaller than the zero-field resistance. The magnetic-field-angle dependence of the magnetoresistance reflects the symmetry of the Fe(Pc)(CN)(2) molecule. We discuss, according to the scaling relation, the correlation between the magnetoresistance and the molecular spin fluctuation.

DOI： 10.1143/JPSJ.75.033703

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER/PLENUM PUBLISHERS  

Thermal analysis of Ag(DM)(2), where DM = 2,5-dimethyl-NN'-dicyanoquinonediimine, clarified that the salt had an insulating amorphous phase (&gt;= 155 degrees C). Characterization of this and related solid states of Ag(DM)(2) indicated that a photo-induced process should be essential in controlling the number of carriers and thus conduction behavior of the salt by illumination. In fact, while heating could do nothing but make the salt insulating when the sample temperature exceeded 155 degrees C, ultraviolet-visible light illumination (&lt; 155 degrees C) could gradually change the properties to be semiconducting with retaining the crystal lattice (average structure).

DOI： 10.1007/s10909-006-9138-3

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DOI： 10.1080/15421400600698121

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

The conductivity of a silver salt of N,N'-dicyanoquinonediimine irreversibly varied in approximate proportion to an illumination of a wide range of wavelengths. Depending on the illumination conditions, four different states (beta, gamma, delta, and epsilon) were obtained with different structures. The b structure is in particular important, where the formal charge of the N,N'-dicyanoquinonediimine molecules continuously decreased to -0.4 - -0.35 with retaining the crystal structure, when we kept the temperature &lt; 155 degrees C during the illumination. The non-illuminated area of the sample retained its original electrical property with a well-defined interface, which enabled a fabrication of a junction-structure in the single crystal.

DOI： 10.1080/15421400600699012

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：EDP SCIENCES S A  

Charge disproportionation (CD) recently observed in many organic conductors is reviewed. CD is closely related to the charge ordering (CO) but is observed even when no long range CO is established. In a theta-phase BEDT-TTF salt, (BEDT-TTF)(2)RbZn(SCN)(4), an extremely slow dynainics of CD has been observed above T-MI. A similar phenomenon is also observed in the Cs-analog, (BEDT-TTF)(2)CsZn(SCN)(4). However, a spin-singlet ground State Without CD is suggested in this salt at low temperatures. It is shown that alpha-(BETS)(2)I-3 exhibits CD at low temperatures, as in alpha-(BET-TTF)(2)I-3. Recently, an abnormal line broadening has been observed in C-13-NMR of (TMTSF)(2)FSO3 under pressure as well as in Se-77-NMR of lambda-(BETS)(2)FeCl4 in a high field. We expect that both are very likely caused by a large CD among the organic molecular sites.

DOI： 10.1051/jp4:2005131002

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

Molecular materials have been recently spotlighted as promising candidates for advanced functional materials. We have developed a novel and simple doping method for a molecular material which utilizes a light-induced solid state reaction. The electrical behavior of a single crystal of a molecular charge-transfer salt of silver(I) ion qualitatively becomes differed after illumination with ultraviolet-visible (UV-VIS) light. The X-ray photoelectron spectroscopy also demonstrated that there was neutral silver species concentrated in the illuminated part of the pressed pellet sample, while only silver (I) ions were detected in the rest part and non-illuminated samples. Raman spectra of the pressed pellet sample showed that the formal charge of the constituent organic pi-acceptor molecule, which is responsible for the conductivity of this material, varied in accordance with the time of illumination. Illumination with UV-VIS light upon only half of a thin single crystal of the same material transformed it to junction structure, exhibiting a rectifying character. This doping method has opened a new way for fabrication of devices from molecular solids.

DOI： 10.1016/j.synthmet.2005.07.128

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Nearly isotropic two-dimensional sheets of partially oxidized Co(Pc)(CN)2 units were observed to form in a salt with PXX (PXX = peri-xanthenoxanthene), [PXX]2[Co(Pc)(CN)2]· CH3CN. The crystal is semiconducting under ambient pressure but displays stable metallic behavior under high pressure. Copyright © 2005 The Chemical Society of Japan.

DOI： 10.1246/cl.2005.936

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SOC PORPHYRINS & PHTHALOCYANINES  

A unique salt composed of cationic and anionic phthalocyanine complexes has been prepared and structurally characterized. The cationic component is di(pyridine)(phthalocyaninato)cobalt(III) and the anionic one is dicyano(phthalocyaninato)cobalt(III). They arrange alternately in the crystal, forming a two-dimensional sheet with partial it-it overlaps. Copyright (c) 2005 Society of Porphyrins & Phthalocyanines.

DOI： 10.1246/cl.2005.936

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

A new charge-transfer salt of ET with a chloromanganate(II) complex anion has been synthesized and characterized by X-ray structural analysis, resistivity measurements, magnetic susceptibility, electron spin resonance (ESR), and an extended Huckel tight biding (EHTB) band calculation. The crystal has a sheet structure comprised of an a-type two-dimensional (2D) donor arrangement in the bc-plane and insulating sheets of discrete [MnCl4](2-) anions and 1,1,2-C2H3Cl3 (TCE) molecules. Its conducting property exhibits considerable anisotropy, which is of effectively metallic along the b-axis down to 1.2 K under 2.9 kbar and higher pressure. The magnetic susceptibility is approximately reproduced by the Curie-Weiss law with a Weiss temperature of = -(1.35 +/- 0.07) K from 2-300 K. ESR measurements revealed that the 7r-electron system in this salt exhibits Pauli paramagnetism at least at 3.6 to similar to50 K. The band calculation suggests that the HOMO (the highest occupied molecular orbital) band has very small dispersion, almost solely along the b*-axis.

DOI： 10.1246/bcsj.77.1987

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WORLD SCIENTIFIC PUBL CO PTE LTD  

We have studied periodic orbit resonances (PORs) in order to probe the topology of the Fermi surface (FS) of the quasi-1D organic conductor (TMTSF)(2)ClO4 and the quasi-2D organic conductors kappa-(ET)(2)Cu(NCS)(2) and K-(ET)(2)I-3. The FS of (TMTSF)(2)ClO4 consists of a pair of weakly corrugated open sheets, while K-(ET)(2)Cu(NCS)(2) and kappa-(ET)(2)I-3 additionally possess warped cylindrical FS sections. In this paper, we review the POR technique for the straightforward case of (TMTSF)(2)ClO4. We then report on a detailed study of the FS topology for kappa-(ET)(2)Cu(NCS)(2).

DOI： 10.1142/S0217979204026895

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Single crystals of a silver/organic charge-transfer complex are doped by illumination via optical fibers (see Figure). Continuous illumination with UV-visible light induces electron transfer between the organic pi-acceptor and a silver ion in the organic charge-transfer complex in the solid state. Illumination of one half of a single crystal produces a p-n junction rectifier in a single step.

DOI： 10.1002/adma.200400308

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

A tetrathiafulvalene (TTF) pi-radicalcation salt with a unique helical-column structure (see Figure) was constructed using a supramolecular double-helix network of mellitate anions. The TTF radical tends to dimerize in a one-dimensional column, but a twisting distortion induces a kink defect. Utilizing the supramolecular network of a counterion is a promising method for the design of novel functional molecular materials.

DOI： 10.1002/adma.200400495

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Single crystals of mellitate anion ([C-6(COO)(6)H(6-)n](n-)) with piperidinium [C5H10NH2+](3)[C-6(COO)(6)H-3(3-)] (1) and [C5H10NH2+](2)[C-6(COO)(6)H-4(2-)].CH3OH.3H(2)O (2), with 1-methylpiperidinium [C5H10NHCH3+]2[C-6(COO)(6)H-4(2-)]. 2H(2)O (3), and with o-phenylenediammonium [C6H4(NH3)(2)(2+)](2)[C-6(COO)(6)H-2(4-)].2CH(3)OH (4) have been prepared and structurally characterized. In all of the salts, two-dimensional (2D) networks of mellitate anions were formed due to the strong self-organization of the anion. In 1, a 2D hexagon-type network of hydrogen-bond has been observed to form among the anions. This is characteristic of the mellitate anions with n = 3 (n: deprotonation number from the acid). In other salts, a 2D anion network containing either water molecules or -NH3 groups commonly formed. Since the network pattern occurs with different cation species, this hydrogen-bonding unit was determined to be dominant in the n = 2 anion with water and the n = 4 anion with = NH3 species.

DOI： 10.1039/b405097e

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：E D P SCIENCES  

Mellitate anions form hydrogen-bonding infinite networks in the salts with pyridinium cations. The network pattern depends on the number of deprotonation (n) from the mellitic acid; for n = 3, triangular hydrogen-bond units form a two-dimensional sheet, while for 11 = 2, dual 14 hydrogen-bond units induce one-dimensional belts or two-dimensional grids. These self-organizing properties have been utilized for the crystal design of the TTF-type radical cation salts. Crystallization with TMTTF gave two kinds of crystals. One of the radical cation salt crystals consists of a channel network of the anions and one-dimensional columns of TMTTF in the channels. In the other TMTTF salt, the anions with n = 1 form a two-dimensional sheet with methanol molecules. The TMTTF radicals are packed between the sheets with their molecular planes parallel to the anion planes.

DOI： 10.1051/jp4:2004114105

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：E D P SCIENCES  

We obtained three conducting crystals based on a [Fe-III(Pc)(CN)(2)] molecular unit. All crystals showed a large anisotropic negative magnetoresistance arising from the pi-d interaction self-contained in the [Fe-III(Pc)(CN)(2)] unit. The anisotropy is attributable to the anisotropic g-tensor in the [Fe-III(Pc)(CN)(2)] unit. We also obtained a thin film containing [Fe-III(Pc)(CN)(2)]. The film exhibits photocurrent response for the UV irradiation. These features suggest [M(Pc)(CN)(2)] molecular unit is a well-designed one for a building block of molecular devices.

DOI： 10.1051/jp4:2004114128

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：E D P SCIENCES  

In order to examine the possibility of (persistent) carrier doping to molecular crystals by light exposure, some different types of molecular crystals containing photoreactive species are synthesized and characterized. The [Ru(bpy)(3)](2+) cation (bpy = 2,2'-bipyridyl) yielded two different new complexes with [Ni(dmit)(2)](-) radical species, both of which were structurally characterized and turned out to be band insulators. Methy viologen (MV) has been found to yield a new phase of the complex with [Ni(dmit)(2)](-), MV[Ni(dmit)(2)](2). The temperature dependences of electrical resistivity (decreasing with lowering temperature down to 1.0 K) and magnetic susceptibility (Pauli paramagnetism from 300 K to 1.8 K with a hysteresis below - 100 K) clearly indicate that this phase is metallic. The thermoelectric power exhibited similar to0 muVK(-1) from 300 K-4.2 K. This phase turned out to be metastable, and the crystals gradually turned into insulating ones. The effects of UV-VIS light exposure to the conducting and magnetic properties of Ag(DMe-DCNQI)(2) have been studied, and clear differences between the exposed and the pristine crystals were observed. The ESR signal at 3.7 K suggested that the exposed sample should include the Ag(0) species.

DOI： 10.1051/jp4:2004114131

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

We synthesized TPP[Fe-III(Pc)(CN)(2)](2), PTMA(x)[Fe-III(Pc)(CN)(2)](.)y(MeCN), and PXX [Fe-III(Pc)(CN)(2)], a new series of charge-transfer salts containing the axially-substituted phthalocyanine (Pc), [Fe-III(Pc)(CN)(2)](-) In this molecular unit, the pi conduction electron derived from the Pc-ring coexists with the d electron which is a potential source of a local magnetic moment. Therefore various phenomena associated with the interplay between local magnetic moments and conduction electrons are expected. We observed the giant negative magnetoresistance (GNMR) in all the three salts. The GNMR is highly anisotropic for the magnetic-field direction, and reflects the g-tensor anisotropy of the local magnetic moment in the [Fe-III(Pc)(CN)(2)](-) unit. This indicates that the GNMR in these salts originates from the strong pi-d interaction in the [Fe-III(Pc)(CN)(2)](-) unit. (C) 2004 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jpcs.2003.11.011

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

A novel phthalocyanine conductor containing 2-D pi-pi stacks of the partially oxidized Co(Pc)(CN)(2) units has been obtained by the electrochemical oxidation method with PXX. The crystal is highly conductive (&gt; 10(3) S cm(-1)) at all the temperatures measured (5 K &lt; T &lt; 300 K). Though the metallic character becomes clearer compared with the single chain or ladder chain conductors, the 2-D sheet has been found to be still anisotropic.

DOI： 10.1246/cl.2004.128

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

The binuclear Cu complex salts of 1,4,7-trithiacyclononane (9S3) with an inorganic anion (BF4)(-) and with an organic radical anion TCNQ(-) (7,7',8,8'-tetracyanoquinodimethanide) were synthesized and their molecular and crystal structures were examined in connection with the magnetic properties. The new complex cation [Cu(9S3)CN(9S3)Cu](+) varies its charges and magnetic properties depending on the counter anions; [Cu(9S3)CN(9S3)Cu](BF4) (1) was obtained as diamagnetic colorless crystals, while [Cu(9S3)CN(9S3)Cu](TCNQ)2 (2) was obtained as dark blue crystals with antiferromagnetic properties. Complex I crystallized in the monoclinic space group C2/c with a = 26.863(2), b = 7.0878(5), c = 13.4864(8) Angstrom, beta = 116.318(2)degrees. Complex 2 crystallized in the triclinic space group P (1) over bar with a = 12.521(1), b = 20.2698(8), c = 8.0205(4) Angstrom, alpha = 100.688(4), beta = 93.846(5), gamma = 94.953(4)degrees. Both complexes are comprised of cyano-bridged two Cu(9S3) ions with tetrahedral coordination. The X-ray structural study revealed that 1 has two crystallographically equivalent copper(l) atoms, while 2 has two crystallographically independent Cu-I/II sites. The two Cu-I/II sites could not be distinguished from the X-ray structural study. For 2 the IR spectra show that both crystallographically independent TCNQ species were monoanions and are strongly dimerized due to pi-stacking, which well explains their diamagnetic contribution to the magnetic susceptibility and the highly insulating property of this salt. The temperature-dependent magnetic susceptibility of 2 showed a deviation from the Curie-Weiss behaviour around 60 K, which indicates a strong antiferromagnetic intermolecular interaction between the copper complexes and that such intermolecular interaction should partly occur via the TCNQ radical anion dimer.

DOI： 10.1002/zaac.200400313

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SOC PORPHYRINS & PHTHALOCYANINES  

Solid state properties of dicyano(2,3-naphthalocyaninato)cobalt(III) neutral radical crystal, [Co(2,3-Nc)(CN)(2)]CH3CN, were characterized by measurements of the resistivity under high pressure and under uniaxial strain, thermoelectric power, magnetic susceptibility, ESR and polarized reflectance spectra. The title compound exhibited thermally activated-type electrical conductivity along the c-axis. The room temperature (RT) resistivity rho(RT) along the c-axis and activation energy E-a rapidly decreased with increasing pressure. The temperature-dependent thermoelectric power S was that of a typical one-dimensional (ID) semiconductor. However the high absolute value of S suggested that this electronic system should be strongly correlated. Although the electrical resistivity exhibited monotonous temperature-dependence, the magnetic susceptibility clearly indicated a Peierls-type transition and marked fluctuation from RT. Both Peierls-type transitions and fluctuations are characteristic phenomena to 1D conductors. Furthermore ESR spectra manifested that the Peierls-type transition occurred at 100 K. The inconsistency between the electrical behavior (without a phase-transition) and magnetic behavior (with a phase-transition) indicates separation of the degrees of freedom in spin and charge (spin-charge separation) of this material. Spin-charge separation is a theoretically predicted phenomenon peculiar to the ID conductors with strong correlation. The reflectance spectra were quantitatively explained by a 1D Hubbard model, and manifested the existence of a structural fluctuation of this material from RT. Based on these observed physical properties it is concluded that [Co(2,3-Nc)(CN),]CH,CN is a strongly correlated ID semiconductor with a Mott(Hubbard) type energy gap and characterised with a fluctuation and spin-charge separation. Copyright (c) 2004 Society of Porphyrins S Phthalocyanines.

DOI： 10.1246/bcsj.77.1987

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ACADEMIC PRESS INC ELSEVIER SCIENCE  

An organic charge-transfer (CT) salt (BEDT-TTF)(3)(MnCl3)(2)(C2H5OH)(2) has been synthesized by a standard electrochemical method. The crystal data are monoclinic, C2/c (#15), a = 38.863(4) Angstrom, b = 6.716(1) Angstrom, c = 23.608(3) Angstrom, beta = 115.007(3)degrees, V = 5584(1) Angstrom(3), and Z = 4. The structure consists of one-dimensional (1D) infinite {[MnCl3](-)}(infinity) magnetic chains and two-dimensional (2D) organic conduction pathways. The former consists of face-sharing octahedra of manganese chloride complex ions, and dominates the magnetic properties of this compound. Such a feature of the crystal structure closely relates to transition metal hexagonal perovskite compounds, all of which are known for frustrated triangular lattices comprised of weakly interacting 1D magnetic chains. The new compound exhibits a high conductivity down to 4 K. (C) 2003 Elsevier Inc. All rights reserved.

DOI： 10.1016/S0022-4596(03)00418-3

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMERICAN PHYSICAL SOC  

We demonstrate a new method for determining the Fermi velocity in quasi-two-dimensional (Q2D) conductors. Application of a magnetic field parallel to the conducting layers results in periodic open orbit quasiparticle trajectories along the Q2D Fermi surface. Averaging of this motion over the Fermi surface leads to a resonance in the interlayer microwave conductivity. The resonance frequency is simply related to the extremal value of the Fermi velocity perpendicular to the applied field. Thus, angle dependent microwave studies enable a complete mapping of the in-plane Fermi velocity. We illustrate the applicability of this method for the highly 2D organic conductor kappa-(BEDT-TTF)(2)I-3.

DOI： 10.1103/PhysRevLett.91.216402

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

A novel low-dimensional molecular conductor, [PXX][Fe-III(Pc)(CN)(2)], has been synthesized. This salt contains the magnetic Fe-III ion (S = 1/2), and is isomorphous with [PXX][Co-III(Pc)(CN)(2)] which includes the non-magnetic Co-III ion. In both salts, the [M-III(Pc)(CN)(2)] (M = Fe or Co) units form a two-leg ladder chain. The two salts exhibit a similar temperature dependence of the thermoelectric power and a similar reflectance spectrum. The Fe-III salt shows serniconducting behavior in its electrical resistivity over the temperature range measured, while the isomorphous Co-III salt exhibits metallic behavior in its resistivity above 100 K. The difference in the transport properties between the two salts suggests that the conduction electrons in the Fe-III salt are seriously scattered by the local magnetic moment. Spontaneous magnetization is observed below 8 K in the Felt salt. Upon applying a magnetic field, the resistivity of the Fe-III salt drastically decreases below 50 K. The decrease in the resistivity is highly anisotropic to the field orientation. The field orientation dependence is highly consistent with the g-tensor anisotropy in the [Fe-III(Pc)(CN)(2)] unit, suggesting that the negative magnetoresistance originates from the large pi-d interaction self-contained in the [Fe-III(Pc)(CN)(2)] unit.

DOI： 10.1246/bcsj.76.1935

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

Single crystals of mellitate anion ([C-6(COO)(6)H6-n](n-)) salts with 3-aminopyridinium, [3-NH2C5H4NH+](3-)C-6(COO)(6)H-3 (3-)] (1). 4-methylpyridinium, [4-CH3C5H4NH+](2)[CH3C5H4N](2)[C-6(COO)(6)H-4(2-)] (2), [4-CH3C5H4NH+](2)-C-6(COO)(6)H (2-)(4)].2CH(3)OH (3), pyridinium, [C5H5NH+](2)[C-6(COO)(6)H-4(2-)].2H(2)O (4), 3-methylpyridinium, [3-CH3C5- H4NH+](2)[C-6(COO)(6)H-4(2-)] (5), [3-CH3C5H4NH+](5)[C-6(COO)(6)H-3(3-)]C-6(COO)(6)H-4(2-)].CH3OH (6), and isoquinolinium, [C9H7NH+](2) [C-6(COO)(6)H-4(2-)].CH3OH (7), [C9H7NH+](2)[C9H7NH0.50.5+]C-6(COO)(6)H-3.5(2.5-)].CH3OH (8) have been structurally characterized. In these crystals, strong hydrogen-bonds between the mellitate anions are formed. Various arrangements that depend on the deprotonation number, n, have been found. All hydrogen-bonds found between the anions are combinations of a carboxy and a carboxylato group. The "triangular hydrogen-bond" unit between the anions, in which three anions are connected by the three hydrogen-bonds to form a triangle, in the salt with n = 3, induces the two dimensional (2-D) sheet self-organizing structure in this crystal. "Dual hydrogen-bond" units between the anions, in which two pairs of the hydrogen-bonds connect the neighboring anions, have been found in the salts with n = 2 or 2.5. The repetition of the co-planer "dual hydrogen-bond" induces the anion one-dimensional (1-D) belt structure, while the combination of the standing and co-planer "dual hydrogen-bond" units induces the 2-D grid structure. These 2-D grids are further linked by hydrogen-bonds to form a channel. In all the salts (n = 3, 2, 2.5), the counter cation molecules are arranged in the space defined by the anion network.

DOI： 10.1246/bcsj.76.1351

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

have studied the magnetic susceptibility for one-dimensional system, TPP[Fe(III)xCo(1-x)(III)(Pc)(CN)(2)](2) (0.07 less than or equal to x less than or equal to 1). At x = 1, the system shows anisotropic Curie-Weiss behavior and spontaneous magnetization below 6 K The temperature below which spontaneous magnetization occurs (T-c) shifts downward with a decrease in Fe-III concentration, but is still above 2 K at x = 0.07. The anisotropic Curie-Weiss behavior in the susceptibility was observed for all the alloys measured. This magnetic anisotropy was associated with the g-tensor anisotropy in the [Fe-III...(Pc)(CN)(2)] unit.

DOI： 10.1016/S0379-6779(02)00754-3

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The magnetic torque shows the anomaly around 20K. The torque curve suggests the antiferromagnetic state in the one-dimensional Fe(Pc)(CN)(2) chain. The magnetic easy axis is directed along the CN-ligand in the Fe(Pc)(CN)(2) unit. Because of the strong spin-orbit coupling, the next highest occupied molecular orbital is also ordered so that the molecular orbital angular momentum of the neighboring Fe(Pc)(CN)(2) unit is antiparallel. We observed the weak ferromagnetism below 6K. This is ascribed to the canting of the antiparallel moments.

DOI： 10.1016/S0379-6779(02)01078-0

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The ET salt with a magnetic counter ion (ET)(3)(MnCl4)(TCE) (TCE = 1,1,2-trichloroethane) exhibits pressure-sensitive, complicated electrical behavior due to its semimetallic electronic structure. On the other hand, stronger d-pi coupling is suggested in (ET)(3)(MnCl3)(2)(C2H5OH)(2), which has infinite magnetic chains with semimetallic conducting behavior.

DOI： 10.1016/S0379-6779(02)00794-4

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We measured the electron spin resonance and the magnetoresistance in the iron(Ill) phthalocyanine complexes. The electron spin resonance in PNP[Fe(Pc)(CN)(2)] reveals the large anisotropy of the g-value. This is due to the strong spin-orbit coupling in the second HOMO (the third HOMO) hybridizing the d(yz)(d(zx)) orbital in the central Fe atom. This anisotropic g-value is consistent with the anisotropy of the magnetic susceptibility and the negative magnetoresistance in TPP[Fe(Pc)(CN)(2)](2). We also measured the large negative magnetoresistance in [PXX][Fe(Pc)(CN)(2)] and (PTMA)(x)[Fe(Pc)(CN)(2)](y)(CH3CN). The iron(III) phthalocyanine complexes are the good materials for the research of the one-dimensional pi-d electron system. (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0379-6779(02)00429-0

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Electrochemical oxidation of [Co-III(Pc)X-2](-) yields highly conducting partially oxidized salt crystals. Their crystal structures and dimensionality of the pi-pi interaction (electronic system) vary by the cationic species in the salts; one-dimensional for TPP (tetraphenylphosphonium) or PTMA (phenyltrimethylammonium) cations, and ladder and two-dimensional for the PXX (peri-xanthenoxanthene) radical cation. Substitution of the axial group (X) or extension of the pi-conjugated macrocycle (Pc) has been found to influence the magnitude of the pi-pi stacking interactions. Their electrical properties characterized by the conductivity and thermoelectric power measurements are found to be dependent on the dimensionality and the magnitude of pi-pi stacking interactions. (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0379-6779(02)00431-9

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The title salt was obtained as fine black needles from the electrolysis of ET (ET: bis(ethylenedithio)tetrathiafulvalene) with a Mn cluster in 1,1,2-trichloroethane containing 10% of ethanol. The conductivity at room temperature was 25 S cm(-1) with weakly semiconducting behavior, yet the salt kept a high conductivity down to 4 K (similar to0.1 S cm(-1)). The manganese(II) chloride anion formed an infinite chain made of face-shared MnCl6 octahedrons, and these chains formed insulating sheets with ethanol molecules between the chains. The ET cation radicals formed alpha'-type conducting sheets between the insulating sheets. Such crystal structure was characterized as that of a typical hexagonal perovskite ABX(3), where A equals to a bulky monocation. The magnetic behavior was reproduced by the Curie-Weiss law, which might be attributable to the face-shared MnCl6 octahedron chains. (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0379-6779(02)00269-2

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We have measured the angular dependence of the ESR spectra on DMDP[(Fe0.01Co0.99III)-Co-III(Pc)(CN)(2)] (DMDP = dimethyldiphenylphosphonium, Pc = phthalocyanine), which is the alloy system of magnetic Fe-III and non-magnetic Co-III. The spectra exhibit giant anisotropic shift in g-value of iron(III). We also report the temperature dependence of the polarized reflectance spectra of one-dimensional conductors, TPP[Fe-III(Pc)(CN)(2)](2), and TPP[Co-III(Pc)(CN)(2)](2) (TPP = tetraphenylphosphonium). With lowering the temperature, the plasma edge drastically shifts to a higher wavenumber in both salts. (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0379-6779(02)00341-7

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Three kinds of the 1:1 Ni(dmit)(2) salts with 4-(4-pyridyl)pyridinium (PP), 4-12-(4-pyridyl)ethenyllpyridinium (P = P), and 4-[2-(4-pyridyl)ethyl]pyridinium (P-P) cations have been prepared and structurally characterized. All of these crystals are composed of a multi-dimensional network of the Ni(dMit)(2) anions and the hydrogen-bonding one-dimensional cation chains. Compared with tight hydrogen bonds in the P = P and P-P chains, that in the PP chain is rather loose. The P = P and P-P salts show semiconducting behavior with high resistivity and large activation energy, while the PP salt shows the opposite temperature dependence with low resistivity at high temperature. The thermoelectric power indicates that the PP salt is an n-doped semiconductor. The proton defects may occur in the loosely bound PP chain which results in the carrier doping in the conduction band formed by the pi-pi interaction of the Ni(dmit)(2) anion radicals. (C) 2002 Elsevier Science (USA).

DOI： 10.1006/jssc.2002.9751

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The magnetoresistance study on TPP[M(Pc)(CN)(2)](2) (M = Fe, Co, Fe0.30CO0.70) salts is reported. These three salts have similar columnar structures, nevertheless exhibit different electrical behaviors. TPP[Fe(Pc)(CN)(2)](2) exhibits anisotropic giant negative magnetoresistance, while TPP[Co(Pc)(CN)(2)] exhibits large positive magnetoresistance. The alloyed compound, TPP[Fe-0.30 Co-0.70 (Pc)(CN)(2)](2), also exhibits anisotropic negative magnetoresistance, although the decrease in the resistivity under the magnetic field is less than that of TPP[Fe(Pc)(CN)(2)](2). The g-tensor anisotropy in the [Fe(Pc)(CN)(2)] unit qualitatively explains the field-orientation dependence of the negative magnetoresistance. Magnetic fluctuation associated with a weak-ferromagnetic transition is suggested as a possible origin of the giant negative magnetoresistance. (C) 2002 Elsevier Science (USA).

DOI： 10.1006/jssc.2002.9736

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With the axially CN-substituted phthalocyanines, novel one-dimensional conductors, (PTMA)(x)[M-III(Pc)(CN)(2)].yCH(3)CN (M = Co and Fe) have been obtained. Although their crystal structures appear as if they were simple salts, their physical properties show metallic behaviors, These crystals are therefore partially oxidized salts in which part of the cation sites are replaced by CH3CN. Especially, when M = Fe, the Pc unit has a local magnetic moment and a 1-D pi-d system is formed. The existence of the pi-d interaction is suggested from the electrical and magnetic measurements.

DOI： 10.1080/10587250290102017

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We will report on the synthesis of some new metal-dithiolene-derivative complexes which are considered to be promising components for new organic conductors. They include 1) unsymmetrical metal-dithiolene complexes with terminal cyano groups and 2) metal-complexes with radialene-type ligands. The group 1) complexes are designed for extended intermolecular interaction via the CN groups. In the course of this study a double-decker type Ni-complex has been synthesized and structurally characterized. The group 2) complexes are designed with the expectation that the pi-conjugation on a molecule expanding towards two different directions should enable two-dimensional molecular overlapping modes. Spectroscopic data and X-ray structural study have revealed that they have well-developed conjugated pi-electronic systems over the whole molecule and thus good planarity.

DOI： 10.1080/10587250290102891

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A novel dimerized Ni-dithiolene complex, (n-Bu4N)(2)[Ni(dmit)(i-mm)](2) (1), was synthesized and characterized by X-ray structure analysis. In this complex two [Ni(dmit)(i-mnt)] units were mutually connected by two long axial Ni-S bonds. The single crystals of TTF, BEDT-TTF and EDT-TTF salts with [Ni(dmit)(1-mnt)](2)(2-) were prepared by electrocrystallization and characterized by X-ray analyses. The Ni-S bonds of each dimer were also retained in these salts. Each salt exhibited semiconducting behavior.

DOI： 10.1080/10587250210784

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A series of the layered tin-iodide perovskite compounds with a general formula (RNH3)(2)SnI4 have been prepared. The RNH3 species adopted are normal-alkyl ammonium, cyclic-alkylammonium, and phenylethylammonium, and as the (RNH3)(2) unit alkyldiammonium is adopted. The obtained single crystals have been subjected to X-ray diffraction experiments. The structures of the SnI42- layers, their bond lengths and angles, are widely varied depending on the cationic organic species between the perovskite layers.

DOI： 10.1080/10587250290102891

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The C-2v isomer of Co(1,2-Nc-C-2v) (1,2-Nc = 1,2-naphthalocyaninato) has been isolated by fractional crystallization of the crude mixture of four isomers (C-4h, C-s, C-2v, D-2h), and its crystal structure, electronic absorption, and magnetic circular dichromism have been discussed.

DOI： 10.1246/cl.2001.260

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The magnetic and crystal structures of the [Ni(dmit)(2)](-) (dmit = 1,3-dithiol-1,2-thione-4,5-dithiolate) simple salts with N-alkylated cationic derivatives of pyridyl nitronyl nitroxide radical (N-R-PYNN) have been studied. In the system with p-nBuPYNN (p-N-nbutyl-), [Ni(dmit)(2)](-) is found to form ladder chains similar with those found in p-EPYNN[Ni(dmit)(2)]. The magnetic susceptibility in this salt shows spin-ladder behavior.

DOI： 10.1016/S0379-6779(00)00615-9

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A novel dimerized Ni-dithiolene complex, (n-Bu4N)(2)[Ni(dmit)(i-mnt)](2), was synthesized and characterized by X-ray structure analysis. In this complex two [Ni(dmit)(i-mnt)l units were mutually connected by two long axial Ni-S bonds. The single crystals of BEDT-TTF and TTF salts with [Ni(dmit)(i-mnt)](2)(2-) were prepared by electrocrystallization and characterized by X-ray analysis. The Ni-S bonds of each dimer were also retained in both salts. Both salts exhibited semiconducting behavior with the room-temperature resistivity rho (rt) / Omega cm = 10(2), 10(3), respectively.

DOI： 10.1016/S0379-6779(00)01530-7

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The title compound (ET=bis(ethylene)dithiotetrathiafulvalene TCE=1,1,2-trichloroethane) is a new molecular conductor obtained by the standard electrochemical oxidation. It has a beta " -donor arrangement without any crystallographic disorder or non-integral stoichiometry. The electrical behavior, which was sensitive to pressure, was semiconducting (35 Scm(-1) at RT) at ambient pressure with a clear hump around 60 K accompanied by a large hysterisis. No corresponding anomalies, however, were observed in its temperature-dependent magnetic susceptibility. The calculated band structure is two-dimensional, which agrees well with the observed physical properties.

DOI： 10.1016/S0379-6779(00)00826-2

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We found the giant negative magnetoresistance in TPP[Fe(Pc)(CN)(2)](2) below 50K, The magnetic susceptibility shows a highly anisotropic Curie behavior. Under the field along the a-axis (the c-axis), we observed the large (small) negative magnetoresistance and the large (small) magnetic susceptibility. This experimental results suggest the pi -d interaction between the one-dimensional conduction electrons and the local magnetic moments. We proposed the field-induced reduction of the spin scattering of the conduction electrons by the local moments as the origin of the negative magnetoresistance. In the isostructural compound TPP[Co(Pc)(CN)(2)](2) without magnetic moments, we observed large positive magnetoresistance. The experimental result of the Go-compound suggests that the local moments are essential for the mechanism of the negative magnetoresistance of the Fe-compound.

DOI： 10.1016/S0379-6779(00)00997-8

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We have observed periodic orbit resonances in the normal state of the organic superconductor kappa-(ET)(2)I-3 Frequency dependent studies allow for a determination of the cyclotron mass, which can then be compared with the effective mass obtained by other techniques. Tilting the sample in the applied magnetic field enhances the resonance harmonics and enables investigation of the warping of the nearly cylindrical Fermi surface; our findings confirm recent theoretical predictions for quasi-two-dimensional conductors.

DOI： 10.1016/S0379-6779(00)00931-0

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Three kinds of charge-transfer (CT) complexes of PXX (PXX = 6, 12-dioxaanthanthrene) have been newly prepared and structurally characterized. In the 1:2 CT complex with TNP (TNP = 2,4,6-trinitrophenol), PXX is practically neutral. In the semiconducting partially oxidized salt with I-3,the PXX molecules form a trimer and each PXX is formally oxidized by e/3. In the 3:2 salt with [Ni(mnt)(2)](-) (mnt = maleonitriledithiolate),the PXX molecules again form a trimer unit and each PXX is formally oxidized by 2e/3. Together with the structural data obtained from the PXX single component crystal, the molecular geometry change by the formal charge on PXX has been examined. A noticeable change has been found in the aromatic ring framework, which is consistent with the distribution of the HOMO coefficients obtained from the extended Huckel calculation.

DOI： 10.1246/bcsj.74.53

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An electrolysis of bis(ethylenedithio)tetrathiafulvalene (ET) and a Mn-cluster in a 1,1,2-trichloroethane solution containing 10% (vol/vol) of ethanol yields black lustrous single crystals, β″-(ET)3(MnCl4)(1,1,2-C2H 3Cl3) based on the X-ray structural study. The crystal structure can be characterized as alternating two-dimensional donor sheets and insulating sheets made of isolated [MnCl4]2- ions and the 1,1,2-C2H3Cl3 molecules. Every pair of the neighbouring donor molecules has a large displacement along both short and long molecular axes. A tight-binding band calculation suggests that this arrangement should lead to a weak but isotropic intermolecular interaction in the donor sheets, and this in turn should lead to a marginally metallic or semiconducting electronic structure. Although the polarized reflectance spectra and the temperature-dependent spin susceptibility derived from the EPR spectra on the single crystal indicate metallic nature, the electrical behaviour under atmospheric pressure is semiconductive with room temperature conductivity of 35 S cm-1 and apparent activation energy of 0.023 eV. It exhibits a resistive hump with hysteresis at around 60 K, which could be associated with a structural transition demonstrated by a series of low temperature X-ray oscillation photographs. The magnetic susceptibility at 4.5-300 K does not exhibit any anomaly and is well reproduced by the Curie-Weiss model with Curie constant C/emu K mol-1 = 3.89 and Weiss temperature θ/K = -0.10. This magnetic behaviour can be quantitatively understood as the sum of Pauli paramagnetism of the π-electrons and the contribution from the local spins on the Mn(II) ions with d5-configuration (S = 5/2). High pressure easily suppresses the increase in resistivity at low temperature, and the electrical behaviour is particularly sensitive to the first 3-5 kbar.

DOI： 10.1039/b102786g

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Air-oxidation of the acetone-acetic acid solution Of (C7H13NH)(2)[Pd(dmit)(2)] yielded black shiny platelets of (C7H13NH)[Pd(dmit)(2)](2). The crystal structure was characterized by a criss-cross columnar structure, which has been often observed in M(dmit)(2)-based (M = Ni, Pd) superconductors. Although the quinuclidinium cation (C7H13NH)(+) is found to be orientationally disordered on a 2-fold axis, the crystal exhibited metallic conductivity down to similar to 40 K. Under ambient pressure the room temperature conductivity is around 22 S cm(-1) and the resistivity gradually decreased with decreasing temperature down to 200 K, where it suddenly started to decrease more rapidly and kept decreasing down to similar to 40 K, where it started to increase steeply. At ea. 200 K the structural transition occurred, yet the crystal and molecular structures remained practically unaffected including the cation site disorder and the strong dimerization of the Pd(dmit)(2) molecules. The electrical behaviour under high pressure was rather unusual but could be compared with structurally related Pd(dmit)(2)-based superconductors.

DOI： 10.1039/b102260c

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Electrochemical oxidation of PTMA[M-III(Pc)(CN)(2)] (PTMA=phenyltrimethylammonium, Pc=phthalocyaninato, and M=Co or Fe) gives partially oxidized salts (PTMA)(x)[M-III(Pc)(CN)(2)].y(solvent) (solvent=acetonitrile or acetone). The obtained crystals in which the solvent molecules partially occupy the cationic sites are isomorphous regardless of M and solvent. They are highly conducting and metallic behavior is observed in the conductivity and thermoelectric power measurements. In contrast to the Pauli-like behavior of the Co-III salt, Curie-like behavior with an anomaly due to antiferromagnetic interactions was observed for the Fe-III salt in magnetic susceptibility measurements. The existence of local magnetic moments in the Fe-III salt leads to a significant influence on the transport properties, suggesting the existence of pi -d interactions in this system.

DOI： 10.1039/b100623l

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A charge-transfer complex of DAP with F(4)TCNQ has been obtained by electrochemical reduction of F4TCNQ in acetonitrile in the presence of DAP . BF4. The crystal comprises segregated one-dimensional columns of donors and accepters with CH3CN as the crystal solvent. The molecular geometry and infrared spectrum show that the donor and acceptor components are completely ionized. These features are the same as those found in DAP.TCNQ. However, a marked difference lies in the column structure; both the DAP and F4TCNQ columns are composed of the dimerized units, while they are uniform in DAP.TCNQ. The difference can be accounted by the increase of the transfer energy in DAP .F(4)TCNQ . CH3CN compared with DAP.TCNQ.

DOI： 10.1246/bcsj.73.2231

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We have found giant negative magnetoresistance in the one-dimensional conductor TPP[Fe(Pc)(CN)2]2 below 50 K. The reduction of the resistance is larger in the field perpendicular to the one-dimensional axis than parallel to the axis. The magnetic susceptibility shows anisotropic Curie-Weiss behavior. The experimental results suggest the interaction between the one-dimensional electron system and the local moments. The reduction of the spin scattering of the itinerant electrons by the local moments under the field is proposed as the origin of the giant negative magnetoresistance.

DOI： 10.1103/PhysRevB.62.5839

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

We have found giant negative magnetoresistance in the one-dimensional conductor TPP[Fe(Pc)(CN)(2)](2) below 50 K. The reduction of the resistance is larger in the field perpendicular to the one-dimensional axis than parallel to the axis. The magnetic susceptibility shows anisotropic Curie-Weiss behavior. The experimental results suggest the interaction between the one-dimensional electron system and the local moments. The reduction of the spin scattering of the itinerant electrons by the local moments under the field is proposed as the origin of the giant negative magnetoresistance.

DOI： 10.1103/PhysRevB.62.5839

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A fused polycyclic aromatic compound, rubrene (RB), has been found to form a charge-transfer compound with iodine with the stoichiometry of RB·I9. The crystal is monoclinic, space group C2/c, a = 14.482(4), b = 16.676(8), c = 19.985(4) Å, β = 106.90(2)°, V = 4618(2) Å3, and Z = 4. In this crystal, a unique branched crank-shaped one-dimensional (I9/-)∞ polyiodide chain is formed. RB is surrounded by the polyiodide, and its cation radical state which is unstable under normal conditions, is stabilized. The formation of the RB cation radical has been confirmed by IR, VISNIR, and EPR spectroscopies. The magnetic susceptibility measurement has indicated the existence of superexchange interactions through the polyiodide.

DOI： 10.1246/bcsj.73.61

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DOI： 10.1246/bcsj.73.61

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A conducting partially oxidized salt of TPP[Fe(Pc)(CN)(2)](2), which contains paramagnetic iron(III), has been obtained by electrocrystallization of TPP[Fe(Pc)(CN)(2)]. The crystal is composed of one-dimensional TPP arrays surrounded by slipped-stacked one-dimensional Fe(Pc)(CN)(2) chains. This structure is isomorphous with TPP[Co(Pc)(CN)(2)](2), in which the central metal is non-magnetic cobalt(III). The electrical conductivity at room temperature, ca. 10 Omega(-1)cm(-1), is about one order of magnitude lower than that of the Co analogue. On lowering the temperature, the conductivity shows a much steeper decline compared with the temperature dependence of the conductivity of TPP[Co(Pc)(CN)(2)](2). The band width, estimated from both thermoelectric power measurements (which show apparent metallic behavior at high temperatures) and an extended Huckel calculation, is found to be the same as that obtained for TPP[Co(Pc)(CN)(2)](2). This is consistent with observations from the single-crystal reflectance spectra, in which both partially oxidized salts show almost the same plasma edge. On the other hand, the magnetic susceptibility of TPP[Fe(Pc)(CN)(2)](2) is quite different from that of TPP[Co(Pc)(CN)(2)](2); both of the magnetic moments originated from Fe-III and the pi-radical seem to be localized in TPP[Fe(Pc)(CN)(2)](2), while the moments originated from the pi-radical in TPP[Co(Pc)(CN)(2)](2) are interacting with each other to lead to temperature-independent Pauli-like susceptibility. At low temperatures, a decrease in the susceptibility has been observed, suggesting the existence of antiferromagnetic interactions.

DOI： 10.1039/a909159i

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Electrochemical oxidation of the dicyano(2,3-naphthalocyanato)cobalt(III) anion ([Co(2,3-Nc)(CN)(2)](-)) yields electrically conducting crystals comprised of the Co(2,3-Nc)(CN)(2) neutral radicals and some crystal solvents. The oxidation of the potassium salt in acetonitrile gives Co(2,3-Nc)(CN)(2). CH3CN, while that in a mixed solvent of acetonitrile/o-dichlorobenzene (DCB) gives Co(2,3-Nc)(CN)(2). 2DCB. X-Ray structure analyses show that two- or three-dimensional pi-pi stacking interactions are achieved in these crystals. Compared with the phthalocyanine (Pc) derivatives this higher-dimensionality in the 2,3-Nc radical crystals, even with a large crystal solvent, arises from the linear extension of the pi-conjugation system of Pc.

DOI： 10.1039/b004025h

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We found the giant negative magnetoresistance in the one-dimensional pi-d system TPP[Fe(Pc)(CN)(2)](2) below 50K. The large negative magnetoresistance was observed for the field along the a-axis, while the small one along the c-axis. We also observed the anisotropic Curie behavior of the magnetic susceptibility. The large (small) magnetoresistance was observed in the field orientation for the large (small) magnetic susceptibility. The reduction of the spin-flip scattering of the itinerant electrons by the local moments under the magnetic field was proposed as the origin of the negative magnetoresistance. In the isostructural compound TPP[Co(Pc)(CN)(2)](2) we observed the large positive magnetoresistance. This positive magnetoresistance cannot be explained in terms of the orbital effects under the field.

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Electrically conducting neutral radical crystals can be obtained by electrochemical oxidation of dicyano(phthalocyaninato)cobalt(III) anion, [Co(Pc)(CN)(2)](-). The electrolysis of the potassium salt in DMSO gives Co(Pc)(CN)(2). 2DMSO. The solvent-free crystal can be obtained by electrolysis of K[Co(Pc)(CN)(2)] in acetonitrile in the presence of various second components or using salts with other cations. The intermolecular pi-pi overlap is efficient in the solvent-containing crystal, while that in the solvent-free crystal is much less. The electrical resistivity at room temperature of the latter has been found to be 4.5 x 10(3) Omega cm, which is nearly three orders higher than that of Co(Pc)(CN)(2). 2DMSO. Copyright (C) 1999 John Wiley & Sons, Ltd.

DOI： 10.1002/(SICI)1099-1409(199912)3:8<720::AID-JPP164>3.3.CO;2-R

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The crystal and magnetic structures of the 1:1 salts of [M(dmit)(2)](-) (M = Ni and Au) with the p-EPYNN (p-N-ethylpyridinium cr-nitronyl nitroxide) cationic radical have been studied. Both crystals contain one-dimensional p-EPYNN chains with alternate head-to-tail orientation. In this chain a ferromagnetic interaction has been found to operate in common. Similarly, there is a common feature in the arrangement of M(dmit)(2); in both crystals M(dmit)(2) forms a one-dimensional chain through intermolecular S...S contacts between the outer rings of the ligand. However, a marked difference exists in the arrangement of these chains. The one-dimensional Au(dmit)(2) chain is sandwiched between the p-EPYNN chains, resulting in isolation of each one-dimensional Au(dmit)(2) chain. On the other hand, every two chains of Ni(dmit)(2) are sandwiched between the p-EPYNN chains, resulting in the Ni(dmit)(2) ladder-chain formation. In contrast to the absence of the unpaired electron in [Au(dmit)(2)](-), the presence of the unpaired electron in the frontier orbital of [Ni(dmit)(2)](-) plays an important role in the formation of an antiferromagnetic molecular spin ladder.

DOI： 10.1021/ja991058k

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Paramagnetic Fe(III) has been introduced into molecular conductors based on axially substituted metal phthalocyanine for the purpose of constructing a system which has magnetic spins on the conduction paths. Some crytstals have been obtained from the electrochemical oxidation of [Fe(III)(Pc)(CN)(2)](-). The crystal structures are the same as the cases where the metal ion is Co(III), but their physical properties are quite different.

DOI： 10.1016/S0379-6779(98)00502-5

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Some new complex molecules of transition metals with an ET-like ligand and bridging like cyano groups were synthesized.

DOI： 10.1016/S0379-6779(98)00596-7

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The magnetoresistance of alpha-[(CH3)(2)(C2H5)(2)N][Ni(dmit)(2)](2) has been studied at ambient pressure in magnetic fields of up to 60 T and under hydrostatic pressures of up to 6 kbar in fields of up to 17 T. The high field measurements indicate a very simple Fermi surface. Measurements in medium fields, however, indicate several quantum oscillation frequencies, whose weight gets reduced with increasing field in favour of the major gamma-orbit. The low field alpha- and beta-orbits exhibit a strong pressure sensitivity. Whereas no quantum oscillations were observed at 2 kbar, shifted alpha-and beta-frequencies occur at a pressure of 6 kbar.

DOI： 10.1016/S0379-6779(98)00487-1

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The tautomeric structures in solid phase were studied by near-edge X-ray absorption fine structure (NEXAFS) and X-ray photoelectron spectroscopy (XPS) for five N-salicylideneaniline derivatives. The observed features in the NEXAFS spectra were assigned by (1) the comparison with the core excitation spectra of reference compounds and (2) ab initio MO calculations of the core-excited states by the improved virtual orbital method. The relative intensity of the observed peaks characteristic of each tautomer enabled us to deduce the tautomeric structures of these compounds. The XPS spectra allowed quantitative estimation of the relative tautomer populations. These structures are consistent with the previous estimation by Xray diffraction. These results demonstrate the usefulness of NEXAFS as well as XPS for studying the tautomerism in hydrogen bonded systems.

DOI： 10.1021/ja991058k

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Two polymorphs of 1 : 1 charge-transfer complexes of DAP-BRL were grown from a benzene solution. The gamma-form is triclinic, space group P (1) over bar, a = 16.53(1), b = 17.80(1), c = 8.235(5) Angstrom, alpha = 96.42(7), beta = 97.76(6), gamma = 120.79(5)degrees, V = 2015(3) Angstrom(3) and Z = 4; the delta-form is monoclinic, space group Po, a = 6.862(3), b = 9.891(2), c = 15.246(2) Angstrom, beta = 101.78(2)degrees, V = 1012.9(5) Angstrom(3), and Z = 2. Both crystals comprise mixed stacks of donors and accepters. The molecular geometry, the CO stretching frequencies, and the EPR spectra indicate that most of the component molecules in both crystals are in the neutral state. The electrical conductivity is, however, found to be high; especially the value for gamma DAP-BRL (10(-1) Omega(-1) cm(-1)) is unusually high as a neutral mixed-stack complex.

DOI： 10.1246/bcsj.72.21

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Electrochemical oxidation of PXX and [Co(Pc)(CN)(2)](-) in acetonitrile gives a highly conducting crystal containing two-leg ladder chains of the partially oxidized Co(Pc)(CN)(2) units. The doubling of the one-dimensional chains makes the electrical properties quite different from those in the single chain conductor.

DOI： 10.1016/S0379-6779(97)80317-7

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New Ni-complexes [(C4H9)(4)N](n)[Ni(C8H4S8)(CN)(2)] (n = 1, 2) have been synthesized and characterized in order to understand a change in the chemical property and electronic structure of bis(ehtylenedihthio)tetrathiafulvalvene molecule by introducing a transition metal with small bridging ligands in place of an ethylene group. The effect of such a metalation has turned out to be larger than that of any alkylation.

DOI： 10.1246/cl.1998.723

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A highly conducting partially oxidized salt of TPP[Co(Pc)(CN)(2)](2) can be obtained by electrocrystallization of TPP[Co(Pc)(CN)(2)]. The crystal is composed of one-dimensional TPP arrays surrounded by slipped-stacked one-dimensional [Co(Pc)(CN)(2)] chains. The electrical conductivity at room temperature is quite high, 120 Omega(-1) cm(-1), though at low temperature it is weakly semiconducting. The band width for this stacking mode has been estimated from both thermoelectric power measurements and an extended Huckel calculation. The latter suggests that the band width value for the slipped-stacking mode is about 40% of the value for the face-to-face stacking mode. The width estimated from the metallic temperature dependence of the thermoelectric power is actually in excellent agreement with that estimated from the calculation.

DOI： 10.1039/a800123e

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Electrochemical oxidation of the solution containing benzo[c]phenothiazine (B[c]PT) and dicyanophthalocyaninatocobalt(III) anion, [Co(Pc)(CN)(2)](-), gives crystalline solids containing cyano-bridged cobalt-phthalocyanine dimer units. The dimeric species which may exist in equilibrium with the monomer is selectively trapped by crystallization with the B[c]PT cation radical.

DOI： 10.1039/a707540e

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We report the anisotropy of the upper critical magnetic field and the pressure-temperature phase diagram for a molecular superconductor, α-EDT-TTF[Ni(dmit)2], which is a charge-transfer salt formed between EDT-TTF and Ni(dmit)2. The critical field was found to be almost isotropic within the conductive ab-plane. The pressure-temperature (P-T) phase diagram shows decreasing of a superconducting transition temperature by increasing an applied pressure. These results are discussed in connection with the electrical-anisotropy studies reported for the normal-conducting state of this salts. [molecular superconductor, low-dimensional conductor, superconductivity, pressure-temperature phase diagram, upper critical magnetic field]. © 1998, The Japan Society of High Pressure Science and Technology. All rights reserved.

DOI： 10.4131/jshpreview.7.532

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Single crystals of [Me3HN][Ni(dmise)(2)](2), [Me2H2N][Ni(dmise)(2)](2), [MeH3N][Ni(dmise)(2)](2), and Cs[Pd(dmise)(2)](2) were grown electrochemically. The crystal structures of [Me3HN][Ni(dmise)(2)](2), [Me2H2][Ni(dmise)(2)](2) and [MeH3N][Ni(dmise)(2)](2) were determined. Crystal data are as follows: [Me3HN][Ni(dmise)(2)](2) (C15H10NNi2S16Se4), triclinic, P (1) over bar, a=7.606(3)Angstrom, b=17.761(3)Angstrom, c=6.660(2)Angstrom, alpha=100.27(2)degrees, beta=114.93(2)degrees, gamma= 81.84(2)degrees, Z=1;[Me2H2N][Ni(dmise)(2)](2) (C14H8NNi2S16Se4), triclinic, P (1) over bar, a=7.625(3)Angstrom, b=17.583(5)Angstrom, c=6.526(2)Angstrom, alpha=100.01(2)degrees, beta=114.81(5)degrees, gamma=80.82(5)degrees, Z=1;[MeH3N][Ni(dmise)(2)](2) (C13H6NNi2S16Se4), monoclinic, P2(1)/c, a=7.636(2)Angstrom, b=9.545(3)Angstrom, c=22.555(6)Angstrom, beta=92.95(2)degrees, Z=2, Shea contacts between Se atoms across the cation sheet were found in [Me3HN][Ni(dmise)(2)](2) and [Me2H2N][Ni(dmise)(2)](2). A tight-binding band structure calculation by extended Huckel methods indicated that [Me3HN][Ni(dmise)(2)](2) has even stronger intermolecular interactions along the long molecular axis than along the transverse direction owing to a close selenium-selenium contact. Cs[Pd(dmise)(2)](2) kept metallic behavior down to 4 K at ambient pressure.

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The tautomerism in solid phase was studied by near-edge X-ray absorption fine structure (NEXAFS) spectroscopy at the N K- and O K-edges and X-ray photoelectron spectroscopy (XPS) in the N1s and O1s regions for five N-salicylideneaniline derivatives: N,N'-disalicylidene- 1,6-pyrenediamine (DSPY), N'N-disalicylidene-p-phenylenediamine (BSP), N-(2-hydroxy-1-naphthylidene)-1-pyrenylamine (NPY), N,N'-di(2-hydroxy-1-naphthylidene)p-phenylenediamine (DNP), and the complex between DNP and 7,7,8,8-tetracyanoquinodimethane (DNP-TCNQ). The NEXAFS spectral features were assigned by (1) the comparison with the core excitation spectra of reference compounds and (2) ab initio MO calculations of the core-excited states by the improved virtual orbital method using the relaxed Hartree-Fock orbitals. The tautomeric structures were deduced by the intensity of peaks characteristic of the tautomers in OH- and NH-forms. The XPS spectra gave structures consistent with those by NEXAFS and also allowed quantitative estimation of the relative tautomer populations. The results range from the dominance of the OH-form in DSPY and BSP to a comparable mixture of the OH- and NH-forms in DNP and DNP-TCNQ. These structures are consistent with the previous estimation by X-ray diffraction (XD), except for DNP-TCNQ where XD suggested the NH-form dominance. The good correlation of the population by XPS with the C-O bond length by XD supports the present conclusion for DNP-TCNQ. These results demonstrate the usefulness of NEXAFS as well as XPS for studying the tautomerism in hydrogen bonded systems.

DOI： 10.1021/ja9641362

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A series of organic superconductors with tetrahalide GaX4- anions lambda-BETS2GaXZY4-Z (X=Br, Cl, F; 0&lt;z&lt;4; BETS=bis(ethylenedithio)tetraselenafulvalene) are reported together with related BETS conductors. Electric, magnetic and structural properties are briefly described. The resistivity behavior and the superconducting transition temperature have a strong correlation with the size of the anion (or unit cell volume).

DOI： 10.1016/S0379-6779(97)80317-7

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lambda-(BETS)(2)FeCl4, where BETS is bis(ethylenedithio)tetraselenafulvalene, is an organic molecular metal with magnetic anions. It undergoes a metal-insulator transition at about TM-I similar to 8 K. This insulating state can be suppressed and a metallic or highly-conducting state can be restored by applying external magnetic field higher than 10 T. The nature of this phase transition and the ground state, whether a spin-Peierls or antiferromagnet, has not been clarified.
In this paper, we report the anisotropy of magnetic properties of lambda-(BETS)(2)FeCl4 studied using SQUID magnetometer. The temperature dependence of the static magnetic susceptibility below TM-I was found to show a strong field dependence when the field is applied parallel to the crystalline long axis (H//c). The nonlinear behavior in magnetization (M-H), reminiscent of a spin-flop transition of antiferromagnet, is observed at magnetic fields around 1 T, well below the field necessary for restoration of highly-conducting state. This strong field dependence is absent for other magnetic field directions, suggesting that the groundstate of lambda-(BETS)(2)FeCl4 is antiferromagnet rather than spin-Peierls.

DOI： 10.1016/S0379-6779(97)81076-4

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We have investigated magnetoresistance and Hall effect of alpha-(BEDT-TSeF)(2)I-3 at low temperatures on samples under high pressure(14 kbar).
Positive magnetoresistance in law magnetic field (H similar to 0.5 T) and negative magnetoresistance in high field (H &gt; 1 T) are observed at 1.3 K. Hall effect which is nonlinear to the magnetic field is observed.

DOI： 10.1016/S0379-6779(97)80987-3

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BETS (=bis(ethylenedithio)tetraselenafulvalene) conductors with M(CN)(4) anions (M=Pd, Pt) are metallic down to 4K. Crystals of MCl4 salts (M=Co, Ni, In) are metallic down to 4 K. BETS2InCl5[(C2H5)(4)N](0.7) undergoes a gradual metal-insulator transition around 50 K. The magnetic susceptibility of BETS4Cu2Cl6 exhibits a round maximum showing an antiferromagnetic interaction between Cu2+ in Cu2Cl62- anions (J=163 K). The electrical properties and crystal structures of BETS complexes with M(dts)(2) (M=Au, Pd, Pt; dts=dithiosquarate) are briefly mentioned.

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The low-temperature crystal structures of alpha-[(CH3)(2)(C2H5)(2)N][Ni(dmit)(2)](2)(11 K), (C7H16N)[Ni(dmit)(2)](2)(20 K) and gamma-[(CH3)(2)(C2H5)(2)N][Ni(dmit)(2)](2)(4.3 K) were determined by use of new imaging plate(IP) system equipped with He refrigerator. gamma-[(CH3)(2)(C2H5)(2)N][Ni(dmit)(2)](2) was found to be metallic down to 2K with the Pauli-like magnetic susceptibility and to have the round 2D Fermi surfaces at 4.3 K. [(CH3)(3)NH][Ni(dmise)(2)](2) and [(CH3)(2)H2N][Ni(dmit)(2)](2) gave 3D Fermi surfaces owing to the strong intersheet interactions between their selenone groups.

DOI： 10.1016/S0379-6779(97)80930-7

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The temperature dependence of the electrical resistivity of (DED)(2)PF6(THF)(2), where DED is thiadiazoleethylenedithiodiselenadithiafulvalene, is metallic down to similar to 20 K. At lower temperatures the resistivity rises proportionally to the logarithm of temperature, followed by a saturation of the resistivity upturn at around 1 K. The magnetic susceptibility exhibits Curie-like behavior down to similar to 20 K, and chi T suddenly goes towards zero at lower temperatures. Such behaviour indicates that this salt could be a rare example of 'purely organic' systems whose electrical behavior at low temperatures might be best explained as a result of Kondo effect.

DOI： 10.1016/S0379-6779(97)80917-4

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The anisotropy of the upper critical field, Meissner and diamagnetic shielding effect, temperature dependence of magnetic susceptibility were examined for an ambient pressure superconductor, alpha-EDT-TTF[Ni(dmit)(2)]. The upper critical field was found to be almost isotropic within conductive ab-plane. The Meissner and diamagnetic shielding effect revealed that this salt is a bulk superconductor that has a diamagnetic transition of 1.39 K. The magnetic susceptibility does not exhibit any drop suggesting CDW formation.

DOI： 10.1016/S0379-6779(97)80365-7

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Shubnikov-de Haas (SdH) effect and angular-dependent magnetoresistance oscillation (ADMRO) were observed for an organic conductor, kappa-(BETS)(2)GaCl4. The data of SdH oscillation revealed two kinds of closed orbits (alpha- and beta-orbits), having cross-sections of 7.79 x 10(14) cm(-2) and 4.152 x 10(15) cm(-2), respectively. The cyclotron masses for both orbits were estimated to be 1.2m(e) and cm 2.4m(e), respectively. In addition to these SdH oscillations an oscillation attributable to Stark quantum interference (SQI) was observed. The data of ADMRO revealed that the shape of Fermi surface is consistent with the extended Huckel calculation.

DOI： 10.1016/S0379-6779(97)80960-5

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The hybrid donor between bis(ethylenedithio)tetrathiafulvalene and -tetraselenafulvalene (ET and BETS, respectively) has been synthesized and the electrical properties together with the crystal structures of its cation radical salts investigated. All of the crystals studied by X-ray structural analysis turned out to have an orientational disorder at the donor site. Although some of the charge-transfer salts were found to be isostructural with the corresponding ET and/or BETS salts, not all of their electrical properties are parallel to them; some are similar, others are significantly different from those of the parent donor salts. Such a trend indicates that the effect of the disorder on the electrical behavior might not be always equal, and should depend on some factor(s) yet to be clarified.

DOI： 10.1246/bcsj.70.107

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：VCH PUBLISHERS INC  

A new series of organic superconductors is reported: lambda-type salts of bis(ethylenedithio)tetraselenafulvalene (BETS) with mixed halide gallium anions. Their preparation and properties are described, with particular emphasis on the electrical resistivity. A strong correlation is observed between the superconducting transition temperature T-c and the unit cell volume, which should enable the superconducting transition to be investigated systematically and facilitate the design of new organic superconductors with enhanced T-c.

DOI： 10.1002/adma.19960081009

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The ambient-pressure superconductor alpha-(EDT-TTF)[Ni(dmit)(2)], which is a charge transfer salt formed between EDT-TTF and Ni(dmit)(2), exhibits a superconducting transition at 1.3 K and a phase transition around 20 K featuring a characteristic resistance hump.
We estimated that the room-temperature electrical conductivity was 140-370 and 14-36 S cm(-1) for the current parallel and perpendicular to the conducting plane respectively. We measured the upper critical magnetic field (H-c2) in the superconducting phase, The temperature dependence of H-c2 was estimated \dH(c2)/dT\(T=Tc) approximate to -0.27 T K-1 (B parallel to c*-axis); \dH(c2)/dT\(T=Tc) approximate to -3.5 T K-1 (B parallel to ab-plane). The anisotropy of H-c2 within the ab-plane was found to be quite small, indicating a two-dimensionally isotropic character within the ab-plane in the superconducting state of the salt.

DOI： 10.1002/(SICI)1099-0712(199609)6:5/6<367::AID-AMO259>3.0.CO;2-1

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Meissner and diamagnetic shielding effects were investigated for an organic superconductor, alpha-EDT-TTF[Ni(dmit)(2)] (dmit = 4,5-dimercapto-1,3-dithiole-2-thione, EDT-TTF = ethylenedithio-tetrathiafulvalene),under ambient pressure. The onset of the diamagnetic transition occurred at 1.39 K. From the measurements of the Meissner effect, the volume fraction of the superconducting phase was estimated to be more than 62%. From the measurements of the diamagnetic shielding effect, this fraction was estimated to be about 93%. This high level of volume fraction shows that the superconducting phase is the main phase in alpha-EDT-TTF[Ni(dmit)(2)].

DOI： 10.1016/0379-6779(96)80181-0

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The charge transfer salts of newly synthesized donor thiadiazolo(ethylenedisulfanyl)diselenadithiafulvalene (DED) exhibit metallic behaviour down to low temperatures with a unique crystal structure and small S---N distances in addition to an inter-chalcogen network.

DOI： 10.1039/cc9960000521

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PHYSICAL SOC JAPAN  

Electrical resistivity under a high pressure and the upper critical magnetic field (H-c2) in the superconducting state were investigated on the ambient-pressure superconductor alpha-(EDT-TTF)[Ni(dmit)(2)], which exhibits a phase transition around 20 K and the superconducting transition at 1.3 K under ambient pressure. Above 9.9 kbar, the superconducting transition was not observed down to 0.5 K; while the former transition survived up to 13.7 kbar. The temperature dependence of H-c2 was estimated: \dH(c2)/dT\(T=Tc) approximate to -0.27 T/K (B parallel to c*-axis); \dH(c2)/dT\(T=Tc) approximate to -3.5 T/K (B parallel to ab-plane). The anisotropy of H-c2 within the ab-plane was found to be quite small indicating the two-dimensionally isotropic character within the ab-plane in the superconducting state of the salt.

DOI： 10.1143/JPSJ.65.538

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The preparation, crystal structures, and electric and magnetic properties of (BETS)(2)MX(4) molecular conductors (BETS = bis(ethylenedithio)tetraselenafulvalene; M = Mn2+, Fe3+, Co2+, Ni2+, Cu2+; X = Cl, Br, CN) are reported. Resistivity measurements down to 2 K reveal the coexistence of the BETS pi conduction electrons and the localized magnetic moments of the anions in the K-(BETS)(2)FeCl4 and kappa-(BETS)(4)(CoCl4)(C2H3Cl3) salts. Another FeCl4 phase, lambda-(BETS)(2)FeCl4, undergoes a sharp metal-insulator (MI)) transition around 8 K. At the same temperature, a magnetic transition of the FeCl4-anions takes place cooperatively. A superconducting transition is observed at 4.6 K in lambda-(BETS)(2)(FeCl4)(0.5)(GaCl4)(0.5), where half of the anion sites are occupied by magnetic ions. The crystals prepared from 1,1,2-trichloroethane solutions with the NiCl42- and MnCl42- anions exhibit the behavior of a semimetal down to approximate to 100 K. The (BETS)(4)(Cu2Cl6) salt remains metallic down to 4.2 K. ESR studies show that the Fe3+ ions in kappa- and lambda-(BETS)(2)FeCl4 are in a high-spin state. The temperature dependencies of the spin susceptibilities of kappa- and lambda-(BETS)(2)FeCl4 indicate antiferromagnetic interactions between the Fe3+ ions. The crystal structure analyses of kappa- and lambda-(BETS)(2)FeCl4 have been carried out at 298 and 10 K. Closer BETS ... FeCl4 contacts in lambda-(BETS)(2)FeCl4 are observed, which is consistent with the larger Weiss temperature of this compound.

DOI： 10.1016/0038-1098(96)00084-1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：GORDON BREACH SCI PUBL LTD  

Two types of BETS conductors are reported. Needle crystals of lambda-BETS(2)GaX(x)Y(4-x) gave a series of new superconductors: lambda-BETS(2)GaCl(4) (T-c=7 K), lambda-BETS(2)GaBrCl(3) (8 K), lambda-BETS(2)GaCl(3)F (3.5 K), lambda-BETS(2)GaBr(0.5)Cl(3.5) (6.5 K). lambda-BETS(2)GaBr(1.5)Cl(2.5), which is a semiconductor at 1 bar, exhibited a superconducting transition at 8 K and ca. 1 kbar. Pressure and temperature dependencies of the resistivities of lambda-BETS(2)GaX(x)Y(4-x) closely resemble those of kappa-type BEDT-TTF superconductors. Many BETS metals with magnetic ions (Fe3+, Mn2+, Co2+, Cu2+) were prepared. Among them, kappa-type MX(4) (M=Fe, Co; X=Cl, Br) salts and theta-type Cu2Cl6 salts are metallic down to at least 4 K. The static susceptibility of lambda-BETS(2)FeCl(4) shows a characteristic magnetic field dependence below its metal-insulator transition temperature.

DOI： 10.1080/10587259608037913

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Novel electric, magnetic and structural properties of molecular metals based on BETS (=Bis(ethylenedithio)tetraselenafulvalene) molecules and magnetic anions such as FeCl4- and Cu2Cl62- were reported. BETS(2)FeCl(4) has two modifications (kappa and lambda). Unlike kappa-BETS(2)FeCl(4) with stable metallic state down to 2 K, lambda-BETS(2)FeCl(4) exhibited a cooperative electric (metal-insulator) and magnetic (paramagnetic-antiferromagnetic) transition at 8 K. BETS(4)Cu(2)Cl(6) with theta-type arrangement of BETS molecules is metallic down to 4 K. Two Cu2+ ions are bridged by two Cl atoms to form binuclear magnetic anion Cu2Cl62-. The Crystal structure and the temperature dependence of the magnetic susceptibility were briefly described.

DOI： 10.1039/cc9960000521

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier Ltd  

The Shubnikov-de Haas (SdH) effect and angular-dependent magnetoresistance oscillation (ADMRO) were observed in magnetoresistance measurements at 0.5 K for an organic conductor κ-(BETS)2GaCl4. From a frequency of a SdH oscillation, a Fermi surface cross-section perpendicular to the crystallographic b-axis is estimated to be 4.20 × 1015cm-2, which corresponds to 105% of the first Brillouin zone. From the results of ADMRO, a Fermi wave number along the crystallographic c-axis is evaluated to be 0.35 Å-1. Both results are consistent with a band structure calculated on the basis of the extended Hückel method.

DOI： 10.1016/0038-1098(96)00084-1

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The band energy scheme of [(CH3)2(C2H5)2N][Pd(dmit)2]2 at high pressure was discussed and it might be possible that the insulating phase above 7 kbar is related to the 1D metal instability. The low-temperature crystal structures of 2D M(dmit)2(M=Ni,Pd) compounds, alpha-[(CH3)2(C2H5)2N][Ni(dmit)2]2 and (C7H16N)[Ni(dmit)2]2 were determined by imaging plate(IP) system equipped with a closed-cycle herium refrigerator. The X-ray satellite reflections of gamma-(EDT-TTF) [Pd(dmit)2]2 indicating CDW formation below 80 K were also observed by IP system. [(CH3)3HN][Ni(dmise)2]2 has a nearly three-dimensional Fermi surface owing to a strong intersheet interaction between their selone groups.

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Crystals of kappa-(BEDT-TTF)(2)I-3 have been prepared electrochemically from a tetrahydrofuran (THF) solution containing the mixed supporting electrolytes {[(C4H9)(4)N]I-3 (95%)-[(C4H9)(4)N]AuI2 (5%)} and also from a THF solution without [(C4H9)(4)]AuI2. A resistivity drop indicating a superconducting transition was observed at 4.2 K (mid-point). The T-c decreased with increasing pressure (dT(c)/dP = -0.8 K kbar(-1)). The resistivity exhibited an anomaly around 170 K, which was coupled with the structural phase transition accompanied by the change of the space group (P2(1)/c--&gt;P2(1)). The crystal structure was determined at 295, 150 and 10 K. The extinction rule of the X-ray intensity data collected at 295 K confirmed the space group to be P2(1)/c as reported previously. The (h 0 l) reflections at 150 and 10 K revealed the absence of c-glide symmetry. The low-temperature crystal structure analyses showed conformational change of the ethylene groups. The low-temperature band structure calculation based on a simple extended Huckel approximation gave Fermi surfaces consistent with de Haas-van Alphen experiments.

DOI： 10.1039/jm9950501681

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alpha-(EDT-TTF)[Ni(dmit)(2)] comprises crossing columns of EDT-TTF and Ni(dmit)(2) and exhibits unique metallic behaviour with a characteristic resistivity peak at around 14 K. The possibility of the development of the superstructure was examined down to 9 K by using a low-temperature imaging plate X-ray system, but no extra X-ray reflections could be found below 14 K. The 14 K anomaly is, therefore, thought not to originate from charge density wave (CDW) instability New phases of gamma-(EDT-TTF)[Pd(dmit)(2)] and gamma-(EDT-TTF)[Ni(dmit)(2)] were found. gamma-(EDT-TTF)[Pd(dmit)(2)] has parallel columns of EDT-TTF and Pd(dmit)(2) and shows a resistivity anomaly around 80 K. Below 80 K, X-ray satellite reflections indicating CDW formation were observed. gamma-(EDT-TTF)[Ni(dmit)(2)] undergoes a metal-insulator transition at around 100 K.

DOI： 10.1039/jm9950501671

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A new organic superconductor, lambda-BETS(2)GaBrCl(3), exhibits an onset of the superconducting transition at 7.5-10 K with a broad resistivity maximum at 55-60 K and a second resistivity increase below ca. 15 K, probably related to the electron localization effect owing to disorder of the tetrahedral anions; the superconducting state persists up to 14 kbar.

DOI： 10.1039/c39950001225

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The very sharp metal-insulator transition, which occurs at 8 K at ambient pressure in lambda-(BETS)(2)FeCl4 is suppressed when applying magnetic fields &gt; 10T. This unusual phenomenon may be connected to ferromagnetic ordering of the Fe3+ moments, which could drive some ''evaporation'' of the previously condensed conduction electrons, into a field-restored highly conducting state (FRHCS) in which oscillations of the magnetoresistance are reported.

DOI： 10.1016/0921-4526(94)01043-Z

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

We report on the magnetotransport properties, up to 37 T, of the first organic conductor containing magnetic Fe3+ ions, lambda-(BETS)(2)FeCl4, where BETS is bis(ethylenedithio)tetraselenafulvalene. The previously reported very sharp metal-insulator phase transition, which occurs at 8 K under ambient pressure, is suppressed when applying magnetic fields &gt; 10 T. This unusual phenomenon may be connected to a field-induced ferromagnetic ordering of the Fe3+ ion moments. This could result in some kind of ''evaporation'' of the previously condensed carriers, into a field-restored highly conducting state (FRHCS). In this ground state, angular dependence of the magnetoresistance is observed for current flowing perpendicularly to the best-conduction c axis.

DOI： 10.1016/0379-6779(94)03099-R

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Room temperature and low-temperature(13K) crystal and band electronic structures of alpha- (BETS)(2)I-3 (BETS=bis(ethylenedithio)tetraselenafulvalene) were examined by using a newly developed X-ray crystal structure analysis system based on imaging plate(IP) equipped with a closed-cycle helium refrigerator. The X-ray low-temperature studies of (MeBr-DCNQI)(2)Cu (DCNQI =dicyanoquinonediimine) by using IP system have revealed that the structure change mainly associated with the charge ordering of Cu occurs discontinuously at T-MI but the structure change related to the development of CDW on DCNQI stacks is continuous.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

The crystal structure of alpha[(CH3)(2)(C2H5)(2)N][Ni(dmit)(2)](2)(dmit=1,3-dithiol-2-thione-4,5-dithiolate) was determined at 11 K by use of newly developed X-ray system based on the imaging plate(IP) equipped with closed cycle He refrigerator. The space group of C2/c of the high-temperature phase changes to P21/c at low temperature. The extended Huckel tight-binding band calculation based on the 11K structure and the X-ray evidence showing the appearance of the twofold superlattice gave two-dimensional Fermi surfaces, which are consistent with those derived from the experiments on the magnetoresistance oscillation.

DOI： 10.1016/0379-6779(94)02769-U

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

For the purposes of development of new organic conductors and superconductors several unsymmetrical donors derived from BETS were synthesized, some of whose charge-transfer salt have been characterized by X-ray analysis and electrical resistivity measurement.

DOI： 10.1016/0379-6779(94)02799-5

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

We present experimental evidences showing coexistence of superconductivity with CDW (or SDW) in alpha-EDT-TTF[Ni(dmit)(2)], a new ambient-pressure superconductor with donor-acceptor structure. The electrical resistance of this salt exhibits a hump around 10 similar to 14 K and drops at 1.3 K due to the superconducting transition. Based on the electrical anisotropy derived from reflectance spectra and weak-field magnetoresistance, this resistance hump is assigned to the CDW (or SDW) formation within EDT-TTF chain. Above 20 K both EDT-TTF and Ni(dmit)(2) chain contribute to the electrical conduction, while below 10 K electrical conduction is mainly through Ni(dmit)(2) chain. Temperature-pressure phase diagram determined by resistance measurements under pressure is presented.

DOI： 10.1016/0379-6779(94)02747-M

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

Crystal structures and electronic properties of BETS compounds with tetrahedral anions, MX(4) (BETS=bis(ethylenedithio)tetraselenafulvalene: M=Ga; Fe, In; X=Cl, Br) were examined. The salts can be classified into two types (kappa, lambda). All the compounds with so-called kappa-type molecular arrangements retained metallic behavior down to 4 K. lambda-(BETS)(2)GaCl4 demonstrated a a superconducting transition around 8 K. Whereas lambda-(BETS)(2)FeCl4 with the isomorphic h-type structure exhibited a sharp metal-insulator transition at 8 K. Low-temperature X-ray studies showed that the structural difference between lambda-GaCl4 and lambda-FeCl4 salts is very small. The structure analysis of kappa-(BETS)(2)FeCl4 at 18 K indicated that the FeCl4 anion has approximately C-3v symmetry. The ESR measurements revealed the high-spin state of Fe3+ in lambda-FeCl4 salt and and low-spin state in kappa-FeCl4 salt. ESR intensities of kappa- and lambda-FeCl4 salts suggested antiferromagnetic interaction between Fe3+ ions.

DOI： 10.1016/0379-6779(94)02683-P

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Both of the newly synthesized [Me(3)HN][Ni(dmise)(2)](2) and (EDT-TTF) [Ni(dmise)(2)] exhibit metallic behaviour around room temperature at ambient pressure; tight-binding band calculation indicates that the former has a nearly three-dimensional Fermi surface owing to a strong intersheet interaction between their selone groups.

DOI： 10.1039/c39950000351

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Language：English   Publisher：AMERICAN PHYSICAL SOC  

DOI： 10.1103/PhysRevB.51.3198

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

The electrical and optical properties were studied concerning alpha-(BETS)(2)I-3 and alpha-(BEDT-STF)(2)I-3, which are isostructural to alpha-(BEDT-TTF)(2)I-3. It has been shown that alpha-(BETS)(2)I-3 and alpha-(BEDT-STF)(2)I-3 undergo metal-insulator transitions at around 50 and 80 K, respectively, and that their electrical resistivities exhibit temperature dependences resembling that of alpha-(BEDT-TTF)(2)I-3 under high pressure. The optical reflectance spectra of these salts show a two-dimensional nature of their electronic structures, and analyses of the spectral data show that the transverse inter-molecular interaction increases in the order alpha-(BEDT-TTF)(2)I-3 &lt; alpha-(BEDT-STF)(2)I-3 &lt; alpha-(BETS)(2)I-3.

DOI： 10.1246/bcsj.68.547

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：EDITIONS PHYSIQUE  

Magnetotransport properties of two isostructural salts, the superconducting lambda-(BETS)2GaCl4 phase and the first organic conductor containing magnetic Fe3+ ions, lambda-(BETS)2FeCl4, where BETS is bis(ethylenedithio)tetraselenafulvalene, have been studied up to 37 T. The previously reported sharp metal-insulator phase transition occurring at 8 K under ambient pressure for lambda-(BETS)2FeCl4 is suppressed when applying magnetic fields &gt; 10 T. This unusual phenomenon may be connected to a field-induced ferromagnetic ordering of the Fe3+-ions moments. This could result in some kind of ''decondensation'' of the carriers, initially condensed below 8 K, into a field-restored highly conducting state (FRHCS). The temperature-magnetic-field (T-H) phase diagram is presented. The angle dependence of the critical field H(c2) has been determined for the superconducting lambda-(BETS)2GaCl4 phase at 4.2 K.

DOI： 10.1209/0295-5075/28/6/009

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

The crystal structures and/or electrical properties of EOTT2X [X = AuCl2, AuBr2, Aul2, Au(CN)2, Ag(CN)2, ICl2, IBr2, I2Br, I3, Br3 and MnCl4, FeCl4, CoCl4, NiCl4] are reported. Concerning the linear anion salts seven (X = AuBr2, Aul2, ICl2, I2Br, I3, Br3) of them were found to be isostructural. Although they apparently have columnar structures, there are many sulfur-sulfur short contacts, which lead to a two-dimensional network in the donor sheet. Their Fermi surfaces were calculated to be closed and elliptical by the tight-binding band approximation. EOTT2FeCl4 is disordered at the anion site and has a dimeric columnar structure along the a axis. The Aul2 salt is metallic down to low temperatures. The IBr2 salt also exhibited decreased resistivity with an inflexion at ca. 110 K and a sample-dependent minimum around 25 K. The metal-insulator (M-I) transitions occurred in AuBr2, ICl2 and Br3 salts at temperatures &gt; 100 K. The other salts [I3, I2Br, AuCl2, Au(CN)2, Ag(CN)2, FeCl4, NiCl4, MnCl4 and CoCl4] are semiconductors. EOTTICl2 is polymorphic: the alpha-type is isostructural with the other linear anion salts with an M-I transition around 145 K. The beta-type is semiconducting and has a dimeric structure. The M-I transition of alpha-EOTT2ICl2 might be explained by a structural transition to a similar insulating state to the beta-type.

DOI： 10.1039/jm9940401559

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

An unsymmetrical donor 4,5-ethylenedithio-4',5'-(2-oxatrimethylenedithio)-diselenadithiafulvalene (EOST)dagger has been synthesized. Single crystals of some charge-transfer salts of EOST have been prepared electrochemically. The crystal structures of EOST and its charge-transfer salts were analysed by X-ray crystallography. The dc resistivities were measured on the single crystals. Eight of the salts with linear anions [(EOST)2I3, alpha-(EOST)2IBr2, beta-type IBr2 salt, (EOST)2ICl2, (EOST)2I2Br, alpha- and beta-type AuBr2 salts and Au(CN)2 salt] retained their metallic conductivity down to low temperatures (less-than-or-equal-to 35 K) and some were found to be isostructural. The overlap integrals of some salts and the tight-binding band was examined for (EOST)2I3. The result suggested that it has a quasi-one-dimensional electronic structure and that EOST molecules interact most strongly in a side-by-side direction. The crystal and electronic structures of (EOST)2I3 are discussed by comparison with the isostructural compound (EOTT)2IBr2 [EOTT: 4,5-ethylenedithio-4',5'-(2-oxatrimethylenedithio)tetrathiafulvalene].

DOI： 10.1039/ft9949000763

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

Crystal structures and electrical properties of BETS compounds with tetrahedral anions, MX4- (BETS = bis(ethylenedithio)tetraselenafulvalene; M = Ga, Fe, In; X = Cl, Br) were examined. Every kappa-type salt is metallic below 50 K. Lambda-(BETS)2FeCl4, which is isomorphous to the superconductor GaCl4 salt, undergoes a sharp metal-insulator transition at 8 K.

DOI： 10.1246/cl.1993.2179

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

Lambda-(BEDT-TSF)2GaCl4 has revealed to be a new organic superconductor, where BEDT-TSF is bis(ethylenedithio)tetraselena-fulvalene. The onset temperature of the superconducting transition was about 9.5K and the mid-point transition temperature (T(c)) was 8 K. The crystal belongs to triclinic system. BEDT-TSF molecules are arranged to form a ''quasi-stacking structure,'' where four molecules form a repeating unit.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA LAUSANNE  

High-pressure resistivity studies on beta-[(CH3)4N][Pd(dmit)2]2 and [(CH3C2H5)2N]-{Pd(dmit)2]2 have revealed the system to be new molecular superconductors with Tc=6.3 K at 6.5 kbar and Tc=4K at 2.4kbar, respectively, beta-[(CH3)4][Pd(dmit)2]2 has the structure almost isomorphous to the high-pressure superconductor, [(CH3)4N][Ni(dmit)2]2, though they have the dimeric columns of Pd(dmit)2 molecules. The determination of the phase diagram has revealed the existence of a narrow temperature region where the superconducting phase invades into the insulating phase. The crystal of [(CH3)2(C2H5)2N][Pd(dmit)2]2 belongs to triclinic system and has the dimeric columns of Pd(dmit)2. It is of interest that the insulating phase emerges when superconducting state is suppressed at high pressure.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA LAUSANNE  

We have obtained a variety of highly conducting cation radical salts of BEDT-TSeF(BETS)(bis-(ethylenedithio)tetraselenafulvalene) and asymmetrical pi-donors having a half of BETS skeleton, BEDT-STF(bis-(ethylenedithio)diselenadithiafulvalene), EDST((ethylenedithio)diselenadithiafulvalene) and EOST(4,5-ethylenedithio-4', 5'-(2-oxatrimethylenedithio)diselenadithiafulvalene). Crystal structure analysis of cation radical salts of BETS has revealed that BETS molecule has strong tendency to form 2-dimensional molecular arrangement. The crystal structures and electrical conductivities of radical salts of BEDT-STF, EDST and EOST were examined.

DOI： 10.1016/0379-6779(93)90376-8

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA LAUSANNE  

Electrical and structural properties of (R1R2-DCNQI)2M (R1, R2=CH3, Br..., M=Cu, Li,...) were studied. The IR evidence of the mixed-valency of Cu in (MeX-DCNQI)2Cu (X=CH3, Br) is presented. The 10% doping of DBr-DCNQI induces the metal instability of (DMe-DCNQI)2Cu. The three-fold structure develops below the sharp metal-insulator (MI) transition temperature, which suggests the universality of the three-fold structure in the insulating state of DCNQI-Cu system. The P-T phase diagram is depicted. The characteristic ''reentrant metal region'' will be related to the possible existence of ''molecular heavy elecron system''. The metallic state of (MeBr-DCNQI)2Cu was stabilized by doping Li in the Cu sites. The low-temperature X-my crystal structure analysis of three-fold structure of (MeBr-DCNQI)2Cu was made. A simple model of the antiferromagnetic spin tructure is proposed.

DOI： 10.1016/0379-6779(93)90337-V

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA LAUSANNE  

XANES (X-ray Absorption Near Edge Structure) measurement at Cu K-edge is reported in (R1, R2-DCNQI)2Cu (R1,R2=CH3,CH3O,Cl,Br). The valence states of Cu are examined using XANES spectra. The arguments in the valence state using XPS (X-ray Photoelectron Spectroscopy) are reconsidered. XANES spectroscopy can give intrinsic information because it is bulk sensitive in contrast to the XPS which is surface sensitive. The two groups in DCNQI-Cu family are examined, and it is confirmed that the difference in the spectra exists between two groups. We observed clear change of valence state in group II materials which show metal-insulater(M-I) transition, where the Cu2+ contribution clearly increases below M-I transition temperature. Therefore it is confirmed that the Cu-site is related to the transport property. On the other hand we have seen no marked change in valence for group I materials which are metallic down to low temperatures. And the Cu2+ contribution at room temperature is markedly smaller than that of group II. The valence mixing extents are different between group I and group II even at room temperature.

DOI： 10.1016/0379-6779(93)90452-3

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA LAUSANNE  

Alpha-BETS2I3 and alpha-(BEDT-STF)2I3, which are analogous of alpha-(BEDT-TTF)2I3, exhibit a metal-insulator-(M-I) transition. Polarized reflectance spectrum and magnetoresistarice under high pressure were studied on these salts in order to investigate the electronic structures and the phase transition.
The change of reflectance spectrum accompanying M-1 transition was found to be considerably smaller in alpha-BETS2I3 and alpha-(BEDT-STF)2I3 than in alpha-(BEDT-TTF)2I3.
Application of pressure suppresses the M-1 transition for both salts. Alpha-BETS2I3 becomes metallic under 9Kbar over the whole temperature region. A large positive magnetoresistance is observed in this metallic state alpha-BETS2I3 even at relatively high temperature.

DOI： 10.1016/0379-6779(93)90447-5

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA LAUSANNE  

Several BEDT-TTF salts were synthesized. BEDT-TTF3Br2 and BEDT-TTF-C(CN)3-CuCN were metallic down to 4.2 K. The crystal structure of the former salt was determined. New multi-sulfur TTF derivatives (OTHT, TOTT, and ETT) were synthesized, and their ion-radical salts were obtained by an electrochemical method. We also obtained new donor molecules containing six or seven sulfur atoms which were expected to give new conducting organic salts with two-dimensional electrical properties.

DOI： 10.1016/0379-6779(93)90369-8

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA LAUSANNE  

The electrical resistivities of organic metals with kappa-type molecular arrangements were examined. Superconducting transition temperature (T(c)) of alloy system kappa-[(ET)1-x(STF)x]2 Cu[N(CN)2]Br (ET=BEDT-TTF, STF=BEDT-DSeDTF) is rapidly depressed with increase of the doping amount of the asymmetric pi-donor STF. T(c) becomes lower than 1.6 K at x&gt;0.25 but the system retains metallic state at least up to x=0.6. The characteristic resistivity maximum is smeared with increasing x. The metal-insultor transition of kappa-ET2Au(CN)2 at 70 K is suppressed by applying ''soft pressure'' of about 550 bar. The electrical properties and the crystal structures of kappa-MT2Cu[N (CN)2]X (MT=BMDT-TTF, X=Cl Br) were also examined. The crystal of kappa-MT2Cu[N(CN)2]X belongs to monoclinic system with space group Cc. The structure of anion sheet closely resembles that of kappa-MT2Cu[N(CN)2]X. The electrical resistivity decreases monotonously down to 2 K.

DOI： 10.1016/0379-6779(93)90403-J

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN J APPLIED PHYSICS  

XANES and EXAFS measurements at Cu K-edge are reported for (R1,R2-DCNQI)2Cu. The mixed valence state of Cu proposed in this compound has been confirmed by the XANES study. The systematic XANES and EXAFS studies have revealed differences in the spectra between two groups in this compound (Group I is metallic down to low temperatures, and Group II shows a metal-insulator transition). The local structural change during the metal-insulator transition in the Group II compound has been confirmed using EXAFS analysis. The clear difference in XANES spectra between two groups has been attributed to the difference in the valence states.

DOI： 10.1246/cl.1993.1559

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

[Me2Et2N][Pd(dmit)2]2 is a new molecular superconductor with T(c)=4 K at 2.4 kbar. It is of interest that the insulating phase emerges when superconducting state is suppressed at high pressure. The crystal belongs to triclinic system and has the dimeric columns of Pd(dmit)2.

DOI： 10.1246/cl.1992.1909

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

The superconducting transition temperature (T(c)) was investigated by alloying (BEDT-TTF)2Cu[N(CN)2]Br with (BEDT-STF)2Cu[N(CN)2]Br. The T(C) of the former rapidly decreased with doping the latter. The relation between stoichiometry and structure is also discussed.

DOI： 10.1246/cl.1992.119

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

Four types of the crystals of BEDT-TSeF ("BETS") salts with bromomercurate anions were synthesized electrochemically. The salts with theta- and kappa-type molecular arrangements retain high conductivity down to 4 K.

DOI： 10.1246/cl.1991.1945

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

Superconducting transition of the grease-coated crystal of kappa-(BEDT-TTF)2 Cu[N(CN)2]Cl has been confirmed. There are at least three types of these crystals with different resistivity behaviors, of which the crystal exhibiting a resistivity anomaly around 50 K, undergoes a superconducting transition at 12.5 K, when it is coated with Apiezon L grease.

DOI： 10.1246/cl.1991.1997

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Polarized reflectance spectra of single crystals of (CH3)4As[Pd(dmit)2]2 and Cs[Pd(dmit)2]2 were measured and compared with those of (CH3)4N[Ni(dmit)2]2. Prominent absorption bands, which do not exist in the reflectance spectra of (CH3)4N[Ni(dmit)2]2 were observed around 10000 cm-1 in the spectra of [Pd(dmit)2] salts. Analysis of the reflectance spectra reveals the anomalous electronic structure in these salts where the energy levels derived from HOMO and LUMO of one molecule are partly inverted due to their strongly dimerized structure.

DOI： 10.1016/0038-1098(91)90557-C

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA LAUSANNE  

Visible and infrared reflectance spectra were observed on single crystals of [M(dmit)2] salts. The band parameters of Me4N[Ni(dmit)2]2 were obtained from the reflectance spectra and compared with the results of thermoelectric power measurements. The direct experimental evidences showing the "LUMO-HOMO energy level inversion" are presented for Cs[Pd(dmit)2]2, Me4As[Pd(dmit)2]2, and Me4N[Pt(dmit)2]2.

DOI： 10.1016/0379-6779(91)91396-R

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA LAUSANNE  

In order to probe the conduction band structure and the inter-molecular interactions, we have investigated the polarized infrared reflectance spectra of single crystals of theta- and kappa-(BEDT-TTF)2I3, (BEDT-TTF)2KHg(SCN)4, Me4N[Ni(dmit)2]2 and alpha-(Et2Me2N)[Ni(dmit)2]2. From the low temperature spectra, the Drude parameters are estimated by a Drude-Lorentz curve-fitting. Analyses of the plasma frequencies based on tight-binding band model afford the estimation of transfer integrals of these salts. The shape of Fermi surface and the conduction band structure are deduced by using these parameters.

DOI： 10.1016/0379-6779(91)91412-4

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

We report a series of measurements of the structural and electronic properties of the molecular conductor Cs[Pd(dmit)2]2 (dmit = isotrithionedithiolate). This material has a C2/c structure with stacks of the acceptor groups arranged in sheets separated by the cations, with appreciable dimerization of the acceptor groups along the stack direction. It shows metallic properties at room temperature. We have characterized this material with measurements of conductivity, thermopower, magnetic susceptibility and polarized optical reflectivity, and we find that the electronic structure is quite isotropic in the plane of the acceptor sheets. On cooling, there is a metal-insulator transition at 56.5 K, and this opens an energy gap at the Fermi energy. This transition is associated with a complex periodic lattice distortion comprising an incommensurate modulation and also a commensurate distortion, which breaks the C centring symmetry. We present a calculation of the electronic band structure using an extended Huckel formalism, and show that, owing to the strong dimerization along the stack direction, the Fermi energy lies halfway in a band of highest occupied molecular orbital character. We consider also how the observed structural instability is able to produce an energy gap over the whole Fermi surface, and propose a model that requires coupling between the two types of modulation.

DOI： 10.1088/0953-8984/3/8/007

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：GORDON BREACH SCI PUBL LTD  

DOI： 10.1080/00268949008036007

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

DOI： 10.1246/cl.1989.1839

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