Singlet excited state dynamics of uracil and thymine derivatives: A femtosecond fluorescence upconversion study in acetonitrile

The excited state properties of several uracils have been studied in acetonitrile by femtosecond UV fluorescence upconversion. The fluorescence decays are faster in acetonitrile than in aqueous solution showing that the excited state deactivation mechanism, which involves out-of-plane motion of the 5-substituent, is sensitive to the solvent.