Mechanisms of antioxidant action: A photochemical study of transition metal dibutyl dithiocarbamates (and their photo-stabilizing role in a polyolefin matrix)

Abstract

Solution photochemistry of some ( N, N-di- n-butyldithiocarbamato) complexes and of the metal-free dithiocarbamate ligands has been used to investigate their role in the photo-oxidation of polyolefins. Transient absorption spectra were recorded for tetramethyl thiuram disulphide at around 600 and 400 nm, and for tetramethyl thiuram monosulphide which also shows an additional band at 350 nm. Kinetic analysis of the decay profiles showed the presence of two different species with first and second order kinetics for the 400 and 600 nm transients respectively. Tentatively, the 400 nm absorption was assigned to a triplet-triplet transition, while the 600 and 350 nm absorption regions were assigned to the dithiocarbamoyl and thiocarbamoyl radicals respectively. Spectrophotometric monitoring has shown that tetramethyl thiuram disulphide is formed during the process of photobleaching of the Fe(III) complex.