Liquid crystals of gold(I) N-heterocyclic carbene complexes

Abstract

Three types of Au(I) N-heterocyclic carbene (NHC) and imidazole (Im) complexes, namely [Au(NHC)Cl], [Au(NHC)(Im)][NO₃], and [Au(NHC)₂][NO₃], with two-, three-, and four-N-long alkyl chains, respectively, were synthesized and their mesomorphic properties investigated. Only the [Au(NHC)(Im)][NO₃] series of compounds, adopting an m-shaped conformation in the solid state, showed liquid crystalline properties. For the molecules with three alkyl chains in particular, the Coulombic and hydrogen bonding interactions between the cationic head core and anionic NO₃⁻, and the hydrophobic chain-chain interactions facilitate in sustaining the partially ordered motion, which is not observed for those with two and four arms. These complexes were employed for preparation of stable nanomaterials in organic solvents.