Hydrogen bonding interactions in single component molecular conductors based on metal (Ni, Au) bis(dithiolene) complexes

Abstract

Introduction of hydrogen bonding (HB) interactions in single component conductors derived from nickel and gold bis(dithiolene) complexes is explored with the 2-alkylthio-1,3-thiazole-4,5-dithiolate (RS-tzdt) with R = CH₂CH₂OH through the preparation of the neutral [Ni(HOEtS-tzdt)₂]⁰ (closed-shell) and [Au(HOEtS-tzdt)₂]˙ (radical) complexes. At variance with many other radical gold dithiolene complexes which have a strong tendency to dimerize in the solid state, [Au(HOEtS-tzdt)₂]˙ crystallizes into uniform stacks interconnected by strong O–H⋯N HB involving the nitrogen atom of the thiazole ring. [Au(HOEtS-tzdt)₂]˙ is isostructural with its neutral, closed-shell nickel analog [Ni(HOEtS-tzdt)₂]⁰, a rare situation in this metal bis(dithiolene) chemistry. It demonstrates how the strength of the HB directing motif can control the overall structural arrangement to stabilize the same structure despite a different electron count. The nickel complex behaves as a band semiconductor with weak room temperature conductivity (1.6 × 10⁻⁵ S cm⁻¹), while the gold complex is described as a Mott insulator with a three orders of magnitude improved conductivity (6 × 10⁻² S cm⁻¹).