ELECTRON-SPIN-RESONANCE AND ELECTRON-SPIN ECHO MODULATION STUDIES OF THE PHOTOIONIZATION OF N-ALKYL-N,N',N'-TRIMETHYLBENZIDINES IN AOT REVERSED MICELLES

N-Alkyl-N,N',N'-trimethylbenzidines (C(n)TMB, n = 1, 4,8,12,16) were photoionized in rapidly frozen reversed micelles composed of sodium bis(2-ethyl- 1 -hexyl) sulfosuccinate or aerosol dioctyl (AOT) in isooctane with 4, 9, 14, 24, 34, and 44 mole ratios of water/AOT. The relative photoyields after irradiation with 300-400-nm light were measured by electron spin resonance. The photoyield decreased as the mole ratio of water to AOT increased. This is interpreted as a more negative surface charge density at the organic-aqueous interface as increased water more completely solvates the sodium counterions. The higher negative surface charge density forms a higher barrier for the photoelectron to surmount to enter the water pool. Electron spin echo modulation spectroscopy was used to probe the local magnetic nuclear environment of the photoproduced cation radicals in these reversed micelles and indicate that the cation radicals are located near the interface. Secondary radicals due to interaction of the AOT headgroup with photoelectrons are observed and assigned.