Micellar promoted photoreduction of ethylenediaminetetraacetato cobaltate(III) by 1-benzyl-1,4-dihydronicotinamide

Abstract

The photoreduction of ethylenediaminetetraacetato cobaltate(III)([Co(edta)]^–) by 1-benzyl-1,4-dihydronicotinamide (BNAH) has been studied in the presence of the surfactants cationic dodecyltrimethylammonium chloride (DTAC) and anionic sodium dodecylsulphate (SDS). Cationic DTAC accelerates the photoreduction of [Co(edta)]^–, while anionic SDS suppresses the reaction The micellar effects on the reaction rates have been analysed by distribution of the reactants between an aqueous phase and a micellar phase and monitoring the difference in rate. In the DTAC micellar system, cationic micelles promote the reaction significantly by concentrating the photoexcited BNAH and [Co(edta)]^– through hydrophobic and electrostatic interactions in spite of the smaller rate constant in the micellar phase compared with that in the aqueous phase. On the other hand, anionic SDS hinders approach of the anionic [Co(edta)]^– to the photoexcited BNAH in the SDS micelles, so as to retard the reaction rate.