Blue Luminescent Copper(I) Complexes Bearing a Diphosphine Dioxide Ligand and Enhancement of Emission in the Solid State under Argon

A series of copper(I) complexes bearing a bis(diphenylphosphoryl)amide (dppaO2–) ligand and a diphosphine ligand were synthesized, and their photophysical properties were investigated. Two complexes, [Cu(dppaO2)(DPEphos)] {DPEphos = bis[2-(diphenylphosphanyl)phenyl] ether} and [Cu(dppaO2)(XANTPHOS)] [XANTPHOS = 9,9-dimethyl-4,5-bis(diphenylphosphanyl)xanthene], show bright white-blue and deep blue luminescence, respectively, in the solid state. The quantum yield of [Cu(dppaO2)(XANTPHOS)] is 0.76 under argon and 0.38 under air. The emission decay curves under argon [τ = 7.9 (17 %), 30.0 µs (83 %)] in the solid state are longer than those under air [τ = 2.5 (19 %), 13.9 µs (81 %)]. The photophysical properties of the complexes are discussed together with the results of DFT and time-dependent DFT (TD-DFT) calculations.