ENDOR of perylene radicals adsorbed on alumina and silica-alumina powders. I. The ring protons

Abstract

Complex electron-nuclear double-resonance (ENDOR) spectra were obtained from the radicals formed on activated alumina and silica-alumina powders exposed to solutions of perylene in benzene. Use of deuterated solvent to suppress spectral contributions from proton matrix effects enabled more detailed analysis of resonances associated with hyperfine interactions of ring protons of the perylene radical ion. A model of isotropic Zeeman interactions (g) and very anisotropic hyperfine splittings (A) is supported by multifrequency EPR measurements and ENDOR simulations devised for this work. All three proton hyperfine interactions of the perylene radical ion were resolved and the absolute values of the principal elements of the hyperfine coupling matrices were obtained. The fact that these values for radicals formed on alumina and silica-alumina were nearly identical implies that the same radical species forms on both surfaces. These findings are discussed and the radical is assigned as the cation. © 1987.