Structural and spectroscopic studies of the photophysical properties of benzophenone derivatives.

The effect a solvent has on the photophysical properties of a series of benzophenone derivatives, all FDA approved for use in sunscreens, is examined. Experimentally significant differences in the solvatochromic behavior are found to be dependent upon the substituents on the parent benzophenone molecule. The spectral trends do not appear to originate from only changes in the solvent polarity but indicate that specific solvent-solute interactions influence the absorbance energies of some benzophenones. Computational investigations examine the structure and electronic excitation energies of the molecules. Specific interactions of the solvent and solute are modeled to evaluate structural changes that result from solvent-solute complexation and the impact of the changes upon absorbance properties. The viability of an intramolecular excited state proton transfer is theoretically evaluated. The combination of experimental and computational analysis provides a more complete understanding of the molecular level origin of the unique photophysical properties of this class of UV absorbers.