Masateru Taniguchi

Synthesis, Structures And Properties Of Cyclopenteno Annelated Bis-Fused TTF Donors And Their Molecular Complexes

Abstract A series of cyclopenteno annelated bis-fused TTF derivatives (CP-TTP 1a-d) have been synthesized. The present donors have produced many molecular complexes showing high conductivity. In particular, several cation radical salts based on the bis(methylthio)- (CPTM-TTP 1c) and ethylenedithio (CPET-TTP, 1d) derivatives are metallic down to liquid helium temperature, though resistivity of CPTM-TTP salts increases a little at low temperature. Among metallic salts, (CPTM-TTP)4X (X = PF6 −, AsF6 − and SbF6 −) are isostructural and have two-dimensional “β-type” arrangement of donor molecules. The band calculations of these salts indicate they have eclipsed Fermi surfaces characteristic of two-dimensional metals.

Genuine organic magnetic semiconductors: electrical and magnetic properties of the TCNQ and iodide salts of methylpyridinium-substituted verdazyl radicals

Two kinds of iodide salts of 3-(4- and 3-methylpyridinium)-1,5-diphenylverdazyl radical cations ([p-MePyDV]+I− n(1) and [m-MePyDV]+I− n(2)) and four kinds of 1 ∶ 1 and 1 ∶ 2 salts of the same verdazyl radical cations with tetracyanoquinodimethanide (TCNQ) anion ([p-MePyDV]+[TCNQ]− n(3), [m-MePyDV]+[TCNQ]− n(4), [p-MePyDV]+[TCNQ]2− n(5), and [m-MePyDV]+[TCNQ]2− n(6)) have been prepared, and the magnetic susceptibilities (χM’s) have been measured between 1.8 and 300 K. Salts (1) and (2) behave as one-dimensional (1D) alternating and nonalternating Heisenberg antiferromagnets with exchange interactions of 2JI-II/kB n= n−171 ± 4 K (alternation parameters α n= nJI-III/JI-II n= 0.5) and 2J/kB n= n−15.4 ± 0.9 K (α n= 1), respectively. The χM of (3) follows the Curie–Weiss law with a Curie constant of 0.365 K emu mol−1 and a positive Weiss constant of +2.1 ± 0.2 K, indicating disappearance of a net magnetic moment due to the formation of strong spin pairs in TCNQ anion molecules. The χM of (4) shows a broad maximum at Tmax n= 24 ± 1 K. The χM can be well reproduced by the sum of the contributions from i) a 1D Heisenberg antiferromagnetic alternating-chain system with 2J1/kB n= n−47 ± 2 K (α n= nJ2/J1 n= 0.9) and ii) a dimer system with 2J/kB n= n−636 ± 30 K. The susceptibilities of (5) and (6) showed anomalous magnetic behavior that cannot be explained by a simple model. The separate contributions of the verdazyl cation and TCNQ anion subsystems to the total magnetic susceptibility of the salts were evaluated from measurements of the temperature dependence of the g-value. The 1 ∶ 1 salts (3) and (4) are insulators. On the other hand, the pressed pellet conductivity (σ) of the 1 : 2 salts (5) and (6) at 20 °C was σ n= 8.1 × 10−3 and 2.9 × 10−2 S cm−1 with activation energy of EA n= 0.092 ± 0.005 and 0.091 ± 0.005 eV, respectively. The two 1 ∶ 2 salts (5) and (6) are new genuine organic magnetic semiconductors.

(CPDT-STF)(TCNQ): a new charge-transfer complex metallic down to low temperature

Abstract A new charge transfer complex (CPDT-STF)(TCNQ) has been prepared. An X-ray crystal structure analysis revealed that this complex is composed of the donor and acceptor sheets orthogonally arranged to each other, which is similar to (ET)(TCNQ) and (ET)(TCNQF 1 ). The band calculations indicate that the CPDT-STF layer has a significantly two-dimensional interaction, while the TCNQ one has a one-dimensional Fermi surface. The electrical resistivity of the present complex showed metallic temperature dependence down to 0.6xa0K. The thermoelectric power was negative and changed from the positive to the negative gradient at 60xa0K. The static magnetic susceptibility and transport properties indicate coexistence of local and itinerant electrons in the present complex.

Preparation and properties of gold complexes with TTF dithiolato ligands

Abstract Several gold(III) complexes with TTF dithiolato ligands have been prepared as the tetrahexylammonium salts. The cyclic voltammograms in DMF showed two or three pairs of redox waves. X-Ray structure analysis of Ph4P·Au(eodt)2·(DMF)2 reveals that the Au(eodt)2 anion takes a significantly folded chair conformation. Charge-transfer salts of Au(dt)2 derivatives with TCNQ showed high conductivity (σrt = 100−101 S cm−1 on a compressed pellet).

Synthesis and properties of methylthio substituted ST-TTP derivatives

A new ST-TTP donor TMEO-ST-TTP, where TMEO-ST-TTP is 2-[4,5-bis(methylthio)-1,3-diselenol-2-ylidene)-5-(4,5-ethylendioxy-1,3-dithiol-2-ylidene)-1,3,4,6-tetrathiapentalene, has been prepared. It affords highly conducting PF 6 - and AsF 6 salts retaining metallic conductivity down to 4.2 K, while the TCNQ complex and ClO 4 - salt are low conductive semiconductors. X-Ray structure analyses reveal that (TMEO-ST-TTP)(TCNQ)(PhCl) has a DA type mixed stack, and that the donor array of (TMEO-ST-TTP) 2 ClO 4 (DCE) in the conducting sheet resembles β-BEDT-TTF salts.

Structures and properties of ethylenedioxy substituted CH-TTP

Most of the organic conductors based on CH-TTP derivatives, where CH-TTP is 2-(4,5-cyclohexeno-1,3-dithiol-2-ylidene)-5-(1,3-dithiol-2-ylidene)-1,3,4,6-tetrathiapentanlene, behave metallic down to low temperatures. An X-ray crystal structure analysis of CHEO-TTP(ReO 4 ) 0.38 revealed that the arrangement of the donors is close to that of the κ-BEDT-TTF salts. The band structure calculated with the tight-binding approximation suggests that the ReO 4 − salt has a closed Fermi surface similar to those of the κ-type superconductors.

Microscopic Investigation of a New Two-Component Organic Conductor with Itinerant and Localized Spins: (CHTM-TTP)2TCNQ

Low-temperature electronic phases in a new two-component organic conductor, a segregated-stack charge-transfer salt called (CHTM-TTP) 2 TCNQ, are investigated. The ESR g tensor analyses indicate th...

Structures and properties of alkyl substituted BDT-TTP salts

Abstract Many cation radical salts based on BDT-TTPs substituted with both alkyl and methylthio groups have been prepared. Several salts showed metallic conductivity down to liquid helium temperature. Among them, X-ray structure analysis and band calculation of (CPTM-TTP) 4 AsF 6 reveal that it has β-type arrangement of donors and a closed Fermi surface.