Hydrogen-bonding interactions of photoacids: correlation of optical solvatochromism with IR absorption spectra

The effect of specific hydrogen-bonding interactions on the electronic spectra and the infrared (IR) absorption spectra of several naphthol-type photoacids was investigated. A correlation between the pKa* of the photoacid and its optical solvatochromism was observed for R*OH⋯B-type hydrogen bonds using the Kamlet–Taft (K–T) analysis. In addition, a correlation between the spectral shift in the IR stretching frequency of the ROH⋯B bond and the optical Stokes shift in the fluorescence spectra of the photoacids was found.