Effects of solvent polarity and hydrogen bonding on coumarin 500

The time-dependent density functional theory (TDDFT) is used to investigate the effects of solvent polarity and hydrogen bond on coumarin 500 (C500). Both the absorption maximum and the hydrogen bond strength of C500 hydrogen bonded complex are confirmed to have a linear relationship with the solvent polarity function Δf. The type B (at carbonyl group position) complex whose absorption spectrum is extremely agreement with the experimental results is demonstrated to be preponderant among all the hydrogen bonded complexes. The investigation of C500-phenol complex (type B) shows that the strengthening of hydrogen bond in the S1 state induces the fluorescence intensity of C500 weakened. The solvent polarity is the key influencing factor on intermolecular hydrogen bond by comprising the influence of solvent polarity and substituent on C500.