Molecular orbital studies of luminescent tetranuclear copper(I) complexes

The electronic structures of the tetranuclear copper(I) complexes [Cu4(μ–H2PCH2PH2)4(μ4–E)]2+ [E=S(1c), Se(2c)] and [Cu4(μ–H2PCH2PH2)4(μ4–η1,η2–CC)]2+(3c) have been studied using ab initio molecular orbital calculations. It has been found that the high-lying occupied molecular orbitals contain substantial character from the anti-bonding between the Cu(d) orbitals and the ligand orbitals. These molecular orbitals are also mixed with significant Cu(s,p) character.