N-Alkyl-N,N’,N’-trimethylbenzidines (C(n)TMB, n = 1, 4, 8, 12, 16) were synthesized and photoionized in rapidly frozen anionic, zwitterionic, and cationic vesicles to demonstrate how control of the electron donor location by its alkyl chain length correlates with the photoyield for this new series of molecules. The relative photoyields of the cationic radicals were measured by electron spin resonance. Electron spin echo modulation spectroscopy was used to determine the relative location of the photoproduced cation radical with respect to the deuterated aqueous interface. These relative locations are correlated with the photoyields. The photoyield decreased as the C(n)TMB alkyl chain length increased. This photoyield trend correlates with deeper penetration of the benzidine moiety as a function of alkyl chain length as measured by electron spin echo modulation. Evidence for a relatively inefficient photoinduced radical conversion process in vesicular systems with electron donors is also found.