Single-Component Conductors: A Sturdy Electronic Structure Generated By Bulky Substituents

While the introduction of large, bulky subcharge mobility of organic semiconductors, this crystal engineering strategy is usually avoided in molecular metals stituents such as tert-butyl, -SiMe3, or -Si(isopropyl)(3) has been used recently to control the solid state structures and where a maximized overlap is sought. In order to investigate such steric effects in single component conductors, the ethyl group of the known [Au(Et-thiazdt)(2)] radical complex has been replaced by an isopropyl one to give a novel single component molecular conductor denoted [Au(iPr-thiazdt)(2)] (iPr-thiazdt: N-isopropyl-1,3-thiazoline-2-thione-4,5-dithiolate). It exhibits a very original stacked structure of crisscross molecules interacting laterally to give a truly three-dimensional network. This system is weakly conducting at ambient pressure (5 S.cm(-1)), and both transport and optical measurements evidence a slowly decreasing energy gap under applied pressure with a regime change around 1.5 GPa. In contrast with other conducting systems amenable to a metallic state under physical or chemical pressure, the Mott insulating state is stable here up to 4 GPa, a consequence of its peculiar electronic structure.