ESR investigation of radical cations formed from aromatics and heteroaromatics adsorbed on molybdenum-aluminum oxide surfaces

Abstract

Electron transfer reactions were studied between one-, two-, or three-ring aromatic hydrocarbons or aromatics containing S, O, or N heteroatoms and the surface of the previously described catalyst containing 9% molybdenum on g-alumina The logarithm of the absolute cation concentration or of the ratio of cation concentration to Mo(V) concentration decreased linearly with increasing first ionization potential of the probe molecule. A comparison of anthracene adsorbed on 9% and on 5% molybdenum/alumina catalysts showed that the 9% system had a greater electron-accepting capacity and that the addition of the probe material was a secondary factor in Mo(V) formation. The effects of the support and of pretreatments were also studied. The spectral parameters of the cation spectra were determined by computer fitting.