Solvent effects on the photophysics and photoreactivity of 3-hydroxyflavone: A combined spectroscopic and kinetic study

The photophysical and photochemical properties of 3-hydroxyflavone (3HF) have been investigated in six solvents with different chemical and physical properties: methanol, 2,2,2-trifluoroethanol (TFE), tetrahydrofuran (THF), chloroform (CHCl3), acetonitrile (MeCN), and dimethylsulfoxide (DMSO). The polarity of the solvents and their ability to interact with 3HF by donating and accepting hydrogen bonds were found to strongly influence the UV-Vis absorption spectra and the emission spectra, as well as other photophysical parameters such as fluorescence quantum yield and fluorescence lifetime. In addition, the nature of the solvent was found to influence the kinetics of 3HF photorearrangement to 3-hydroxy-3-phenyl-1,2 indiandione, the reaction being the fastest in TFE, and the slowest in DMSO. The results were interpreted in terms of specific solute-solvent interactions.