Novel conducting copper complexes derived from thiophene-fused DCNQIs and copper(I) iodide

Abstract

An isomeric pair of thiophene-fused dicyanoquinonediimines 1 and 2 have been prepared and reacted with copper(I) iodide to afford a novel class of highly conducting complexes of Cul, which are represented by the formulae 1(Cul)₂ and 2(Cul)₂, respectively. The temperature dependent conductivities of these complexes, as measured from compressed powder samples, exhibited metallic behaviour down to ca. 170 K, with room temperature conductivities of 45 S cm^–1 for 1(Cul)₂ and 100 S cm¹ for 2(Cul)₂. The principal structural features were deduced from EXAFS analysis; the copper ligand environment is composed of an average of three iodine atoms at 2.65 Å and two nitrogen atoms at 1.95 Å. The results were accounted for by a structure composed of polynuclear Cul chains bridged by bidentate ligands 1 or 2. The X-ray powder diffraction patterns of 1(Cul)₂ and 2(Cul)₂ were essentially identical to each other and suggested a highly layered structure. With regard to the electrical transport properties a hole conduction along the Cul chains was suggested by thermoelectric power and X-ray photoelectron spectroscopy measurements.