Spectral behavior and computational studies of fuchsin in various solvents

Absorption spectra of fuchsin were measured in various solvents. Two solvent-dependent absorption maxima were observed between 511 and 538 nm and 552–567 nm. Time-dependent density functional theoretical calculations assigned the transitions between the 510–540 nm and 540–557 nm to π-π* transitions between the HOMO-1 to LUMO and HOMO to LUMO respectively. The absorption data were analyzed using the Kamlet-Aboud-Taft, Catalan and Katritzky models of solvatochromic behavior. The Catalan model was found to provide the best correlation with the experimental absorption maxima, followed by the Katritzky model. Both the Catalan and Katritzky models suggest that polarizability of the solvent is the primary factor affecting the transition energy.