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 [Cu4{P(p-MeC6H4)3}4(mu3-eta(1),eta(1),eta(2)-C[triple bond]C-p-MeOC6H4)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 [Cu4(PR3)4(mu3-eta(1),eta(1),eta(2)-C[triple bond]CR')3]+ complexes, together with density functional theory (DFT) calculations at the PBE1PBE level on the model complex [Cu4(PH3)4(mu3-eta(1),eta(1),eta(2)-C[triple bond]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.