Photochemistry of copper(II) chlorocomplexes in acetonitrile: Trapping the ligand-to-metal charge transfer excited state relaxations pathways

Photochemistry of [Cu(MeCN)(3)Cl](+), [Cu(MeCN)Cl-3](-), and [CuCl4](2-) copper(II) chlorocomplexes in acetonitrile solution is studied by means of the combination of the steady-state photolysis and ultrafast transient absorption methods. The main relaxation pathways of the initially excited ligand-to-metal charge transfer states are internal conversion to the ground state, ionic dissociation without (photo)reduction of copper(II), and radical dissociation with (photo)reduction of copper(II). The copper(II)-to-copper(I) photoreduction quantum yields obtained from steady-state photolysis correlate with ultrafast spectroscopy data. The presence of oxygen does not affect the photoreduction quantum yields, which do not exceed 7% for the complexes studied and decrease in the series: [Cu(MeCN)(3)Cl](+) > [Cu(MeCN)Cl-3](-) > [CuCl4](2-). (C) 2014 Elsevier B.V. All rights reserved.