Excited-state proton transfer in nonaqueous solvent

Excited-state proton transfer from pyranine to urea in methanol solution was studied by using both steady-state quenching and fluorescence lifetime measurements at room temperature. Proton transfer initially requires a urea monomer to form a protonated urea monomer, which is then solvated by methanol. The experimental data demonstrates the emission that would be attributed to an encounter pair. A set of rate constants is obtained on the basis of a simple kinetic model.