Lipophilic contributions to the solvatochromism of analogous betaines

A pair of solvatochromic phenolate betaines that differed only in their lipophilicity was synthesized. Their solvatochromic responses in pure solvents, in a DMSO–MeOH solvent mixture as well as in micellar solutions were different, an observation which confirmed the fact that sensor lipophilicity contributes to the interpretation of solvatochromism. Quantum mechanical calculations reproduced the observed spectral differences. Molecular dynamics simulations shed light on the solute–solvent interactions responsible for their differences in solvent mixtures.