Electron spin resonance, electron spin echo modulation, and electron nuclear double resonance studies of the photoionization of N-alkyl-N,N',N'-trimethylbenzidine in anionic and cationic micelles

Abstract

N-Alkyl-N,N',N'-trimethylbenzidines (C[sub n]TMB, n = 1-6, 8) were synthesized and photoionized in rapidly frozen anionic and cationic micelles. The photoyields of the cation radicals were investigated by electron spin resonance spectroscopy. Electron spin echo modulation spectroscopy and proton matrix electron nuclear double resonance were used to determine the relative location of the photoproduced cation radical with respect to the deuterated aqueous interface. No dependence on the photoyield as a function of the electron donor alkyl chain length is observed, although increasing the alklyl chain length on the benzidine moiety moves its location toward the aqueous interface. The lack of a photoyield trend is interpreted in terms of the solubilization geometry, which determines the paths of electron escape to form charge-separated products. An electron escape cone defined as the solid angle formed from the center of the electron donor moiety through the width of the spin distribution that interests the interface changes only slowly as a function of radical location over a limited range. Hence, the photoyield is little changed. 34 refs., 7 figs., 1 tab.