Picosecond Laser Studies of the Effec?s of Reactants on Intramolecular Energy Relaxation of Diphenykarbene: Reaction of Diphenylcarbene with Alcohols

Picosecond laser induced fluorescence measurements provide for the first time the direct meanrrement of the intramolccular and intermolecular energy decay dynamics of singlet diphenylcarbene (’ DPC) in the presence of reactive molecules. As exemplified by the reaction of ’ DPC with alcohols it is found that reactive molecules provide ’ DPC witi 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 sigtificaat increase in the sin$et state lifetime upon addition of reacting molecules. The absolute reaction rate constants of ‘DPC with alcohols, in different solvents, obtained by direct measurements are also reported.