The Potential of N-Heterocyclic Carbene Complexes as Components for Electronically Active Materials

The application of N-heterocyclic carbene complexes as active sites in materials other than catalysis has been remarkably scarce. Inspired by the - often misleading - 'carbene' label, which implies a substantial degree of M=C pi bonding, we have been interested in evaluating the potential of N-heterocyclic carbene complexes as building blocks for constructing electronically active materials. Electron mobility via the metal-carbon bond has been investigated in monometallic imidazol-2-ylidene complexes and subsequently expanded to polymetallic systems. In particular, ditopic benzobisimidazolium-derived ligands have been explored for the fabrication of bimetallic molecular switches and main-chain conjugated organometallic polymers. Electrochemical analyses have allowed the degree of electronic coupling between the metal sites to be quantified and the key parameters that govern the intermetallic communication to be identified.