Excited-state acidity of bifunctional compounds. 7. Long distance, solvent-assisted excited-state proton transfer in olivacine

By use of fluorescence spectroscopy and time-correlated single photon count ing, solvent-assisted excited-state proton transfer (ESPT) has been observe d for olivacine in two organic solvents, 1,4-dioxane and methanol, Because of spectral overlap, factor analysis was used to determine the emission spe ctrum of the proton-transferred (PT) species. The ESPT is not observed in t he nonpolar solvent n-hexane. For the first time in a system of this type, the individual excited-state rate constants have been calculated exactly fr om time-resolved single photon counting results, Because the PT process inv olves a path of more than 6 Angstrom, its individual rate constant is extre mely low, approximately 107 s(-1).