Photolytic behaviour of [Co(NH 3) 4C 2O 4] in micellar and inverse micellar solutions

Abstract

A comparative study of the charge transfer photochemistry of oxalatotetraaminecobalt(III) perchlorate in pure aqueous solutions and in premicellar and micellar solutions of three different surfactants (anionic, cationic and non-ionic) has been undertaken. The results indicate the following. (1) The quantum yield of Co 2+ (φ Co 2+ ) changes as the concentration of the surfactant changes with a concomitant change i the microenvironment of the probe. The manner in which φ Co 2+ varies depends on the nature of the surfactant used in the solution. The critical micellar concentration (CMC) of a surfactant can be determined from a plot of φ Co 2+ vs. −log[surfactant]. (2) The photoaquation of ammonia does not take place in micellar solutions of sodium dodecylsulphate (SDS) and cetyltrimethylammonium bromide (CTAB), but occurs to a small extent in a micellar solution Triton X-100. The photolysis of the complex has also been carried out in two different inverse micellar microemulsions. The results reveal that the efficiency of the intramolecular photoredox process, as manifested by the quantum yield of Co 2+, decreases as the size of the water pool of the microemulsions decreases.