The Simulation of the ESR Spectra of the Perylene Cation on Solid Surfaces

Abstract

Abstract The simulation of the ESR spectra of the perylene cation formed on the surface of silica gel (with MoO3), silica–alumina, and γ-alumina (with MoO3) was studied. These oxides were pretreated in a vacuum of 10−5 Torr and at 300 °C, and were then brought into contact with a purified perylene solution in benzene. The main parameters which determine the shape of spectra were investigated. By comparing the experimental spectra with the simulated ones, it was concluded that unpaired electron-spin densities on the carbon atoms of the perylene cation are identical to those of the perylene cation in the H2SO4 solution. However, the number of γ-protons which have spin-nuclear interactions with the unpaired electron is three or less. It was found that a considerable part of the line-width is caused by g-unisotropies. If the perylene cation is bound more strongly on the surface, more g-unisotropy is observed and the half-width becomes wider. When the perylene cation is prepared in the air, O2 and H2O molecules coordinate to the perylene cation formed. It was found that the complex cations thus formed have different g-unisotropies and that the ESR spectrum of this cation mixture is structureless, smooth, and a continuous curve.