Properties of Tetrathiotetracene Nickel bis-(ethylene-1,2-dithiolene), A New Quasi-One-Dimensional Conductor.

摘要

The magnetic susceptibility, thermopower, EPR, dc conductivity, and preliminary structural data for a new quasi-one-dimensional (1D) conductor TTT 1.2NiS4C4H4, where TTT is tetrathiotetracene, and NiS4C4H4 is nickel bis-(ethylene-1,2-dithiolene)are reported. The structure consists of 1D chains of stacked TTT units separated by nonstacked NiS4C4H4(-)ions. Charge transfer between TTT and NiS4C4H4 creates NiS4C4H4- ions and a formal charge state +5/6 on the TTT units. The dc conductivity along the TTT chains is thermally activated and is approx. 30/ohm cm at 25 C. The magnetic susceptibility appears to be negligible on the TTT chains and Curie-Weiss-like on the unstacked NiS4C4H4- ions. The thermopower at high temperature is quite small (+1.5 + or -1 micro V/K) and almost temperature independent. The data are reported in terms of a quasi-one-dimensional conductor which is distorted at all accessible temperatures. It is noteworthy that both the crystal field and the Peierls instability are expected to produce the required distortion in this system. (Author)