Synthesis and properties of 2-alkylidene-1,3-dithiolo[4,5-d]-4,5- ethylenediselenotetrathiafulvalene derivatives and crystal structures of their cation radical salts

Abstract

Tetrathiafulvalene derivatives condensed with 2-alkylidene-1,3-dithiole moiety, MeDTES (2-isopropylidene-1,3-dithiolo[4,5-d]-4,5-ethylenediselenotetrathiafulvalene), EtDTES (2-(pentan-3-ylidene)-1,3-dithiolo[4,5-d]-4,5-ethylenediselenotetrathiafulvalene), and CPDTES (2-cyclopentanylidene-1,3-dithiolo[4,5-d]-4,5-ethylenediselenotetrathiafulvalene) have been synthesized. Crystal structure analysis of MeDTES salts with Au(CN)4-, ReO4-,and I3- and a CPDTES salt with I3- reveals that the donor-anion ratios of all salts are 1:1. Band calculation of (MeDTES)[Au(CN)4] suggests a quasi-one-dimensional Fermi surface that could be the result of the uniform stack of donor molecules. In spite of this stacking, the salt is a Mott insulator because of a large on-site Coulomb interaction U. (MeDTES)(ReO4)(H2O)0.5 possesses Fermi points and exhibits semiconducting behavior with small activation energy (Ea = 0.058 eV). I3- ions form disordered infinite chain in (MeDTES)(I3)(DCE)0.25, but those in (CPDTES)(I3) exist as discrete ions. They show low conductivity (10-4-10-2 S cm-1) at room temperature and the band calculation suggests that they are band insulator. © 2011 by the authors; licensee MDPI, Basel, Switzerland.