MAGNETIC-FIELD EFFECTS ON RADICAL PAIRS PHOTOCHEMICALLY DERIVED FROM 2,3,6,7-DIBENZOFLUORENONE

2,3,6,7-Dibenzofluorenone triplets react with triethylamine, 2,4,6-tri methylphenol and ascorbyl-palmitate in micellar solutions to yield rad ical pairs which are sensitive to magnetic field effects whenever sepa ration is inefficient. The three substrates afford three distinctively different scenarios with respect to the confinement of daughter radic als within the micellar phase. Triethylamine and corresponding radical s are soluble in water, which results in rapid entry-exit equilibria w ith the micellar phase, and negligible magnetic field effects. Convers ely, ascorbyl-palmitate and its radicals are virtually insoluble in wa ter, thus bring confined to the micellar phase. Application of an exte rnal magnetic field attenuates the geminate recombination of radicals, probably through slowing down T+ <-> T-0 and T-_ <-> T-0 interconvers ions. The case of 2,4,6-trimethylphenol is intermediate, with the prop ortion of radicals that escape geminate recombination increasing with increasing applied field. The relevance of these reactions in relation to the use of 2,3,6,7-dibenzofluorenone or molecules of comparable so lubility as a tripler probe in biological systems is discussed. (C) 19 98 Elsevier Science S.A.