New asymmetric π-electron donors yielding metallic charge transfer salts

Two new asymmetric π-electron donors derived from tetrathiafulvalene have been synthesized and characterized, and their crystal structures have been determined. One of them, ETEDT-TTF, forms metallic isostructural salts with the octahedral counterions XF6− (X=P, As, Sb), as well as other semiconducting phases. The metallic character of the salts remains til! the lowest temperature measured. In contrast, ETTTF forms only charge transfer salts with relatively high conductivity but semiconducting behaviour. All salts have been studied by electronic paramagnetic resonance, and the crystal structure of the metallic phases have been determined.