Photophysical and Photochemical Studies of Polycyclic Aromatic Hydrocarbons in Solutions Containing Tetrachloromethane. III. Photochemical Interaction of Excited Polycyclic Aromatic Hydrocarbons with Tetrachloromethane in Two-Component Mixtures

Abstract

Abstract In the photoreactions of polycyclic aromatic hydrocarbons with tetrachloromethane in binary mixtures of tetrachloromethane with cyclohexane, benzene and acetonitrile, both the quenching of the fluorescence and the photoreactions run through an intermediate stage which is an exciplex of the excited hydrocarbon with tetrachloromethane. Abnormal quantum yields of the hydrocarbon decrease are interpreted in terms of the appearance of a new reaction channel via a triplex consisting of the excited hydrocarbon, solvent and tetrachloromethane. The photoreaction is quenched by diphenylpicrylhydrazyl, thus suggesting the radical nature of the chemical transformations. A kinetic scheme is suggested for the photophysical and photochemical processes describing the observed phenomena.