External pressure effect on quenching of benz-(a)-anthracene and 9-cyano-anthracene fluorescence by dimethylmercury

Abstract

The effect of external pressure on the interaction between 9-cyano-anthracene or benz-(a)-anthracene in the S₁ state with dimethylmercury has been investigated using n-hexane and acetonitrile as solvents. It appears that 9-cyano-anthracene and dimethylmercury do not form an exciplex in acetonitrile, but that the fluorescence quenching involves a species of higher energy and smaller volume than that of the separated species (Eyring activated complex); in the non-polar solvent the slow fluorescence quenching takes place via a contact complex.

On the other hand, exciplex formation between benz-(a)-anthracene and dimethylmercury, discussed previously on the basis of temperature effects, has been confirmed in the polar solvent. The volume contraction of the system, –9 ± 2 cm³ mol^–1, is consistent with exciplex formation.