Effect of hydrogen bond on solvation dynamics of coumarin153 in cyclohexane-phenol solvent mixtures by time-resolved optical Kerr fluorescence.

Time-resolved optical Kerr fluorescence system was used to investigate time-resolved red-shift of coumarin 153 in different solvent mixtures. The mixtures included four mole fractions of phenol-cyclohexane solvents (0, 0.013, 0.08, and 0.3), and anisole-cyclohexane solvents with the mole fraction of 0.3. The measured time-resolved fluorescence showed that, in the solvent mixtures containing phenol, the time-dependent frequency shift accelerated with the increase in the mole fraction of phenol-cyclohexane mixtures. However, the time-dependent red-shift in the fluorescence was not observed in the anisole-cyclohexane mixture, the solvent polarity could not influence the spectral Stokes shift compared with phenol. The results indicated that coumarin 153 formed an excited hydrogen bond with phenol, and the excited hydrogen bond was strengthened with an increase in the mole fraction of phenol. And, these processes also suggested that the increase in the phenol ratio improves a large number of hydrogen bond formed between phenol and carbonyl group of coumarin 153, the charge distribution will be faster towards lower the free energy of the system due to the stronger dipole moment. Therefore, the corresponding solvation response in phenol-cyclohexane mixtures with higher mole fractions decays very rapidly.