Picosecond laser studies of the effects of reactants on intramolecular energy relaxation of diphenylcarbene: Reaction of diphenylcarbene with alcohols

Picosecond laser induced fluorescence measurements provide for the first time the direct measurement of the intramolecular and intermolecular energy decay dynamics of singlet diphenylcarbene (¹ DPC) in the presence of reactive molecules. As exemplified by the reaction of ¹DPC with alcohols it is found that reactive molecules provide ¹DPC with not only a chemical decay channel but also an intramolecular decay channel which is due to a solvent polarity effect. These chemical and physical effects can act in opposite directions leading to novel results such as a significant increase in the singlet state lifetime upon addition of reacting molecules. The absolute reaction rate constants of ¹DPC with alcohols, in different solvents, obtained by direct measurements are also reported.