A Novel Luminescent μ4-Selenido-Bridged Copper(I) Tetramer

A novel soluble tetranuclear copper(I) cluster containing an unsubstituted μ 4 -selenido moiety, [Cu 4 (μ-dppm) 4 (μ 4 -Se)] 2+ ( 1 ), has been synthesized and characterized by X-ray crystallography. Its photophysical and electrochemical properties have been studied. It is envisaged that the emissions of 1 are associated with a ligand-to-metal charge-transfer LMCT [(Se 2 - ) → Cu 4 ] triplet excited state, and probably with mixing of a metal-centered (3d 9 4s 1 ) Cu(I) state. The phosphorescent state of 1 undergoes facile electron-transfer quenching with a series of pyridinium acceptors. An excited-state reduction potential, E °[Cu 4 (μ-dppm) 4 (μ 4 -Se) 3+/2+* ], of −1.55(10) V vs SSCE has been estimated. Crystal data: monoclinic, space group C 2/ c (No. 15), a = 27.913(9) Å, b = 16.512(9) Å, c = 24.10(1) Å, β = 109.29(2)°, V = 10483(5) Å 3, Z = 4.