Quantum chemical studies in the design of organic metals. II. The equilibrium geometries and electronic structure of tetrathiofulvalene (ttf) andtetracyanoquinodimethane (tcnq) and their uni- and di-valent ions

Abstract

The MINDO/3 SCF MO method has been used to investigate the equilibrium geometries, electronic structure and ground state properties of ttf and tcnq and their uni- and di-valent ions. An analysis of the results indicates that both ttf⁺ and tcnq^- have low energies of disproportionation and that electron addition or removal leads to significant structural change. These considerations are discussed in the light of recent suggestions that at low temperatures the charge- transfer salt (ttf)(tcnq) gives rise to superconducting fluctuations, superimposed on the general characteristics of an organic metal.