Kazuya Kawakami

New Organic Metals Based on Bis-Fused TTF Donors

Abstract A large number of radical-cation salts that retain metallic conductivity down to low temperatures have been prepared on the basis of bis-fused tetrathiafulvalene (TTF) donors. The stable states are associated with inherent tendency of these extended molecules to form two-dimensional conducting sheets. Structural and conducting properties of various TTP salts so far obtained are summarized.

Bis(2-methylidene-1,3-dithiolo[4,5-d])tetrathiafulvalene (BDT-TTF): A tetrathiafulvalene condensed with 1,3-dithiol-2-ylidene moieties

Abstract Four alkyl derivatives of the title donor ( 1a–d ) have been synthesized. The electrochemical properties investigated by cyclic voltammetry and the electric conductivities of charge-transfer complexes with tetrafluoro-tetracyanoquinodimethane and 2,3-dichloro-5,6-dicyano-p-benzoquinone are also presented.

Synthesis and Properties of Higher Homologues of Bis-Fused TTF

Abstract Several derivatives of higher homologues of bis-fused TTF, BDT-TTPY (1) and DT-TTP (2), have been synthesized. Cyclic voltammograms of 1 and 2consist of three-pairs of double-electron and five-pairs of single electron redox waves, respectively. Most of cation radical salts obtained by the chemical doping with appropriate oxidants showed relatively high conductivity ([sgrave]rt =10-2-101 S cm1 on compressed pellets).

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.

Crystal structijus and puysical properties of bis-fused TTF donors

Abstract Bis-fused TTF donors make many highly-conducting radical-cation salts with metallic conductivities down to 3 He temperatures. An overview of crystal structures and physical properties is given.

Preparation, crystal structure and electrical properties of dimethyl substituted unsymmetrical 2,5-bis(1',3'-dithiol-2'-ylidene)-1,3,4,6-tetrathiapentalenes

Preparation, crystal structure and electrical properties of the title compounds 1a–g are described; these donors gave several conducting salts showing metallic temperature dependence.

BDT-TTP donors fused with aromatic rings and their cation radical salts

Abstract Several BDT-TTP derivatives fused with benzene ( 1a-e ) and 1,2,5-thiadiazole ( 2c, f ) rings have been synthesized. Their cation radical salts and TCNQ complexes show high conductivity ( σ rt = 10 −1 −10 3 S cm −1 ). Among them, ClO 4 salt of 1d is metallic down to low temperature.

Conductivity of Radical-Cation Salts of TTP Series Donors under High Pressure

Abstract Anomalous conducting behavior in TTP series salts, particularly (CPTM-TTP)4PF6, where CPTM-TTP is 2-(4,5-cyclopenteno-1,3-dithiol-2-ylidene)-5-(4,5-dimethylthio-1,3-dithiol-2-ylidene)-1,3,4,6-tetrathiapentalene, has been investigated in detail. This charge-transfer salt shows resistivity jumps around 100K, but is still metallic at low temperatures. These jumps are suppressed under applied pressures. Below 30K several sudden drops of resistivity like superconducting transitions are observed, but are not affected by magnetic fields. This anomalous behavior is discussed in view of hysteretic transitions between two metallic phases.

Conducting properties of radical-cation salts of BEDT-TTP

Abstract Compressed pellets of BEDT-TTP chemically doped by such oxydizing reagents as I2 and Br2 have shown high conductivity. Electrochemically obtained EDT-TTP salts have also exhibited metallic conductivity.

Synthesis and properties of bis-fused ttf donors

Abstract A general synthetic method of bis-fused TTF (BDT-TTP) donors has been developed. The parent BDT-TTP has yielded many cation radical salts showing metallic conducting property down to low temperature (≤1.2 K). Crystal and electronic structures of (BDT-TTP) 2 SbF 6 are also presented.