Photocontrol of micellar catalyses

Three photoresponsive surfactants, C₇H₁₅CONHC ₆H₄N=NC₆H₄N⁺Me ₃MeOSO₃^- (1), C₈H ₁₇OC₆H₄N=NC₆H₄ ^- CH₂N⁺Me₃I^- (2), and C₁₆H₃₃OC₆H₄N=NC₆H ₄CH₂N⁺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.