Influence of molecular shape on magnetic field effect on photo-induced geminate radical pair in SDS micellar medium

The magnetic field effects (MFEs) on the dynamics of the two radical pairs (RPs), one generated by photo-excitation of phenyl pyrilium ion (PP+) in the presence of SDS micelles and an electron donor, biphenyl, and the other similarly generated from a SDS micellar solution of biphenyl and trioxotriangulenium carbocation (OXO+), have been compared. At zero field, the RP (PP center dot/BP center dot+) has much higher recombination rate, but much lower escape rate in comparison to the RP (OXO center dot/BP center dot+). The field-dependent yields and lifetimes show saturation early (< 0.1 T) in case of the latter, but in case of the former, the saturation does not occur, not even at a field of 5 T. The results have been interpreted in terms of relaxation mechanism (RM) for MFE and expected differences in the location of the guest in the micellar host, which affects the ratio of the rate of recombination to the rate of escape.