Steady state and time-resolved fluorescence study of 7,8-benzoquinoline: Reinvestigation of excited state protonation

Steady state and time resolved spectral properties of 7,8-benzoquinoline (7,8-BQ) have been reinvestigated in a series of organic solvents of different proticity, polarity and wide range of pH. The salient features of this work are the effect of hydrogen bonding in protonation reaction which is explored through its behaviour in water and strong hydrogen bond donating solvent (trifluoroethanol). Quantum yield and rates (radiative, non-radiative and excited state protonation) have been calculated and discussed. Irreversible diffusion controlled excited state proton transfer in water and faster excited state protonation in trifluoroethanol is observed.