DICATION SALTS OF THE ORGANIC DONOR BIS(ETHYLENEDITHIO)TETRATHIAFULVALENE

Dication salts of the organic pi-donor bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) have been isolated as tetrafluoroborate and perchlorate salts. The salts are prepared by electrocrystallization from an oxidizing solvent mixture. Optical spectroscopy shows that BEDT-TTF is first chemically oxidized to the monocation in the electrolyte media followed by electrochemical oxidation to the dication. BEDT-TTF(BF4)(2) (1) crystallizes in the P2(1)/n space group with a = 5.824(1) Angstrom, b = 9.490(2) Angstrom, c = 17.593(3) Angstrom, beta = 91.61(1)degrees, V = 972.0(3) Angstrom(3), and Z = 2, BEDT-TTF(ClO4)(2) (2) is isostructural to the BF4- salt with a = 5.867(1) Angstrom, b = 9.579(2) Angstrom, c = 17.669(3) Angstrom, beta = 92.06(2)degrees, and V = 992.4(3) Angstrom(3). Optical transmittance spectra from 2 show no evidence for low-frequencey metallic behavior. Two localized transitions at 855 nm (11 700 cm(-1)) and 714 nm (14 000 cm(-1)), each strongly polarized along the crystallographic b axis, are observed by optical reflectance.