Substituent effect on triplet lifetimes of arylketones in benzene solution

The triplet yields and lifetimes of a series of substituted benzophenones have been detemined by their efficiency in sensitizing biacetyl phosphorescence, in benzene solution.The triplet decay constants of nine para-substituted derivatives show a satisfactory Hammett-type correlation. The results are discussed on the basis of a reversible interaction of the excited ketones with the solvent. Possible factors which may be responsible for the inefficiency of sensitization are also discussed.