Luminescent molecular copper(I) alkynyl open cubes: Synthesis, structural characterization, electronic structure, photophysics, and photochemistry

A novel class of tetranuclear copper(I) alkynyl complexes with an open-cube structure was synthesized. The crystal structure of [Cu-4{P(p-MeC6H4)(3)}(4)(mu(3)-eta(1),eta(1),eta(2)-C= C-p-MeO-C6H4)(3)]PF6 was determined. These complexes were found to display dual emission behavior. Through systematic comparison studies on the electronic absorption and photoluminescence properties of a series of [Cu-4(PR3)(4)(mu(3)- eta(1),eta(1),eta(2)-C=CR')(3)](+) complexes, together with density functional theory (DFT) calculations at the PBE1PBE level on the model complex [Cu-4(PH3)(4)- (mu(3)-eta(1),eta(1),eta(2)-C=C-p-MeOC6H4)(3)](+), the nature of their emission origins was probed. Their photochemical properties were also investigated by oxidative quenching experiments and transient absorption spectroscopy.