Charge-transfer photochemistry of copper(II) dithiocarbamate mixed-ligand complexes

The photoredox behaviour of copper(II) diethyldithiocarbamate mixed-ligand complexes, Cu(Et(2)dtc)X (X = Cl, ClO4, NO3), is characterized by strongly allowed ligand-to-metal charge transfer (LMCT) transition in the visible spectra. The reaction from the lowest LMCT state is reduction of copper(II) to copper(I) proceeding via an intramolecular electron transfer from an equatorially bound sulfur atom of the ligand to copper(II). Irradiation of Cu-II(Et(2)dtc)(+) NO3- and Cu-II(Et(2)dtc)(+)... ClO4- in the CT band in CHCl3- iso-propanol (1:1) solutions gave rise to Cu-II(Et(2)dtc)Cl as an intermediate. Final reaction products in all systems were CuCl2 and tetraethylthiuramdisulfide. The mechanism of the primary photochemical reaction is discussed as well as the effect of the anion and the solvent on the transformation of the primary photoproduct. The assignments are supported by EPR data and UV-vis absorption spectra of the complexes.