The Effects of Pressure on the Intramolecular Proton Transfer and Charge Transfer of 4‘-N-Dimethylamino-3-hydroxyflavone

We report the effect of pressure on the intramolecular proton transfer and charge transfer of 4‘- N -(dimethylamino)-3-hydroxyflavone(I) in five polymeric solvents (PAA, CAC, PAN, PMMA, and PVCl). The intramolecular proton transfer and charge transfer are dependent on solvent, excitation wavelength, and pressure. The abnormal absorption and fluorescence spectra of I in PAA and PAN are explained by an interaction between the N, N -dimethylamino group and solvent molecules. The calculated proton-transfer rates show that excited-state intramolecular proton transfer is suppressed by pressure in all five polymers, but to different degrees. The effect of pressure on the fluorescence quantum yield of the normal state is quite different at different excitation wavelengths. When excited at 325 nm, the fluorescence quantum yield of the normal state increases with pressure, then decreases gradually. When excited at 441.6 nm, the fluorescence quantum yield of the normal state decreases with pressure.