Organic metals: BVDT-TTF and BDVDT-TTF polyiodides

In order to experimentally investigate the influence of the steric effects of the ethylene groups in BEDT-TTF on the structure and electroconducting properties of the salts, the authors synthesized polyiodides of two derivatives of BEDT-TTF: bis(vinylenedithio)tetrathiafulvalene (BVDT-TTF), and bis(dimethylvinylenedithio)tetrathiafulvalene (BDVDT-TTF). Comparison of the structure and properties of the (BVDT-TTF)(I/sub 3/)/sub 0.4/ and (BDVDT-TTF) (I/sub 3/)/sub 0.4/ crystals with the (BEDT-TTF)(I/sub 3/)/sub 0.5/ crystals shows that substitution in BEDT-TTF of ethylene bridges for the vinylene bridges, leading to a completely conjugated planar system, probably ensures the possibility of a denser packing of the cation-radicals in the stacks. This results in strong unidimensional anisotropy of the intermolecular interactions, which leads to dielectrization of the electronic system in BVDT-TTF and BDVDT-TTF polyiodides.