CHARGE-TRANSFER PHOTOCHEMISTRY OF COPPER(II) DITHIOCARBAMATE MIXED-LIGAND COMPLEXES

The photoredox behaviour of copper(II) diethyldithiocarbamate mixed-li gand 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 reduc tion of copper(II) to copper(I) proceeding via an intramolecular elect ron transfer from an equatorially bound sulfur atom of the ligand to c opper(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 mechani sm of the primary photochemical reaction is discussed as well as the e ffect of the anion and the solvent on the transformation of the primar y photoproduct. The assignments are supported by EPR data and UV-vis a bsorption spectra of the complexes.