Photocontrol of micellar catalyses

Abstract

Three photoresponsive surfactants, C₇H₁₅CONHC₆H₄NNC₆H₄N⁺Me₃MeOSO₃^–(1), C₈H₁₇OC₆H₄NNC₆H₄CH₂N⁺Me₃I^–(2), and C₁₆H₃₃OC₆H₄NNC₆H₄CH₂N⁺Me₃I^–(3), have been synthesised. The absorption spectrum of 2,6-dichlorophenolindophenol as a probe for micelle formation indicated that the aggregation mode of these photoresponsive surfactants is affected by photoinduced trans–cis isomerisation of the azobenzene head groups. The catalytic activities of these surfactant aggregates in base-catalysed proton abstraction from benzoin and alkaline hydrolysis of p-nitrophenyl cyclohexanecarboxylate were estimated in the dark and under photoirradiation. It was found that the rate constants in the micellar systems change sensitively in response to photoirradiation. The results imply that photoinduced isomerisation of the head groups leads to a change in the catalytic activity. This is the first example of photocontrol of micellar catalysis.