Coinage Metal Complexes of Bis-Alkynyl-Functionalized N-Heterocyclic Carbenes: Reactivity, Photophysical Properties, and Quantum Chemical Investigations.

Bis-phenylpropynyl-functionalized imidazolium salts and their corresponding gold and copper N-heterocyclic carbene (NHC) complexes were prepared in order to investigate their potential application for the synthesis of heterometallic coinage metal compounds. By transmetalation reactions with different precious metal sources, including copper and silver phenylacetylides [MCCPh] (M=Cu, Ag), polynuclear compounds were obtained, which were further investigated for their photoluminescence properties. Additionally, one gold NHC complex was post-functionalized by autocatalytic hydration of the alkynyl side chains. Time-dependent DFT investigations of singlet electronic excitations in representative complexes revealed excited states of diverse character, as determined by the specific complex structure and metallophilic interactions.