Defined tetranuclear coinage metal chains.

To force metal ions in heterometallic coinage metal complexes into preset compartments, we have synthesized a ligand with two N-heterocyclic carbenes (NHCs) separated by a methylene bridge and two bipyridine moieties tethered to each NHC moiety. By using this ligand, tetranuclear heterodimetallic gold/copper and gold/silver complexes were obtained. These complexes show an unprecedented V-shape or linear MAuM (M = Cu, Ag) configuration in the solid state. The photophysical properties of the new compounds are significantly affected by the complexed metal ions.