PHOTOLYTIC BEHAVIOR OF [CO(NH3)(4)C2O4] IN MICELLAR AND INVERSE MICELLAR SOLUTIONS

A comparative study of the charge transfer photochemistry of oxalatote traamminecobalt(III) perchlorate in pure aqueous solution and in premi cellar 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 Co2+ (phi(Co2+)) changes as the c oncentration of the surfactant changes with a concomitant change in th e microenvironment of the probe. The manner in which phi(Co2+) varies depends on the nature of the surfactant used in the solution. The crit ical micellar concentration (CMC) of a surfactant can be determined fr om a plot of phi(Co2+) vs. -log[surfactant]. (2) The photoaquation of ammonia does not take place in miceIlar solutions of sodium dodecylsul phate (SDS) and cetyltrimethylammonium bromide (CTAB), but occurs to a small extent in a micellar solution of Triton X-100. The photolysis o f the complex has also been carried out in two different inverse micel lar microemulsions. The results reveal that the efficiency of the intr amolecular photoredox process, as manifested by the quantum yield of C o2+, decreases as the size of the water pool of the microemulsions dec reases. (C) 1997 Elsevier Science S.A.