ORGANIC METALS CONTAINING TELLURIUM

Examination of the structural and electronic trends among organic metals and organic superconductors, which are composed of complex salts of heterocyclic π-donors, has been greatly facilitated by the preparation and study of a number of new tellurium containing organic π-donors. These studies required that a number of new synthetic strategies be developed. A brief review of these methods leading up to and including the recent synthesis of tetratellurafulvalene (TTeF) is provided. The increase in electrical conductivity on going from S to Se to Te in the series (TXF-TCNQ) (where X=S, Se, Te) is shown to be consistent with the square of the bandwidths or to an increase in intrachain interaction (σ∝wt2). While TTeF-TCNQ has not been found to undergo a transition to a superconducting state as the temperature is lowered at ambient pressure neither does it undergo a metal to insulator transition as is observed for TTF-TCNQ (Tmax = 59K) or for TSF-TCNQ (Tmax = 40K). This change in behavior is likely due, at least in part, to the increased interchain interaction and more two-dimensional character. Tight-binding (extended Hiickel) electronic band structure calculations indicate that while the structure is more 2-D than TTF-TCNQ, the Fermi surface is not closed and the material is still best described as a quasi-one-dimensional organic metal. © 1992, Taylor & Francis Group, LLC. All rights reserved.