Coinage Metal Chalcogenide Clusters with N-Heterocyclic Carbene Ancillary Ligands

This thesis describes the synthesis and characterization of homo- and heterometallic group 11 – group 16 clusters with N-heterocyclic carbene (NHC) ligands. The clusters were prepared from reactive group 11 trimethylsilylchalcogenolate reagents (NHC-M-ESiMe3; M = Cu, Au; E = S, Se, Te) by silane deprotection reactions with phosphine- or phosphite-solubilized group 11 acetates (R3P-M-OAc; M = Cu, Ag, Au). Clusters were characterized by combustion analysis and spectroscopic methods in solution and the solid state. The clusters were phosphorescent at low temperatures with emission energies that depend on the metal/chalcogen composition, ancillary NHC ligand, cluster geometry and nuclearity, and local environment. Lower energy photoluminescence is associated with higher atomic number chalcogenide ligands and correlates with the M→S metal-to-ligand charge transfer energy, for which M = Ag \u3e Cu \u3e Au. Quantum yield of emission is increased in a cluster of high nuclearity and connectivity because of increased molecular rigidity and thermally activated delayed fluorescence. Quantum chemical calculations point to a common mode of emission from all clusters, originating from a charge transfer process from metal-chalcogenide core to the NHC ancillary ligands