CRYSTAL-STRUCTURES AND ELECTRICAL CONDUCTIVITIES OF TXCN-TTF (X=SULFUR, SELENIUM, TELLURIUM - N=2,3) TCNQ CHARGE-TRANSFER COMPLEXES

The crystal structures and the electrical conductivities have been studied for tetrakis(alkylchalcogeno)tetrathiafulvalene (TXC(n)-TTF (X = sulfur, selenium, tellurium; n = 2,3)) complexes with tetracyanoquinodimethane (TCNQ). All the complexes with a composition of 1:1 had the same crystal system (triclinic) and the same space group (P1BAR). The donor and acceptor molecules were alternately stacked in their crystals. (TSeC2-TTF)TCNQ was obtained as plate and needle crystals. The molecular structure of TSeC2-TTF and the overlapping mode between TSeC2-TTF and TCNQ molecules of the two complexes were subtly different. All the complexes were semiconductors because of their mixed-stack structures. (TTeC2-TTF)TCNQ showed the lowest resistivity (5 OMEGA cm at room temperature). Its good conductivity was brought about by the effective degree of charge-transfer and the favorable overlap between TTeC2-TTF and TCNQ molecules. An overall discussion on the structural and physical properties of a series of TCNQ complexes with TXC(n)-TTF (X = sulfur, selenium, tellurium; n = 1,2,3) is presented.