New electron donors: BEDT-TTF derivatives bearing a pyridine group; synthesis, crystal structure, electrochemical studies and the formation of charge transfer complexes

Bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) derivatives 1 a,b and 2 a,b containing a pyridine group have been synthesized and their redox potentials have been studied by cyclic voltammetry in dichloromethane solution, which indicate that they are weaker electron donors than BEDT-TTF. Compound 2b has been studied by X-ray crystallography, which revealed a column-packing pattern in its crystal lattice. The charge transfer (CT) complexes formed between these new donors and tetracyanoquinodimethane (TCNQ), 2,3-diehloro-5,6-dicyanobenzo-1,4-quinone (DDQ)as well as cupric chloride (CuCl2) have been investigated. Among them the CT complexes 1b(1.1) . TCNQ and 1a . CuCl2 show conductivity in the semiconducting range at room temperature (sigma(rt) = 1.6 x 10(-3) S cm(-1) for 1b(1.1) . TCNQ, 4.3 x 10(-3) S cm(-1) for 1a . CuCl2 measured on a compressed pellet). From the results of X-ray photoelectron spectroscopy (XPS) and conductivity measurements, we suggest that charge transfer and coordination contact coexist in the complex 1a . CnCl(2).