STUDIES OF SOLVATION IN HOMOGENEOUS MEDIA BY A SPECTROSCOPIC METHOD - A KETOCYANINE DYE IN NEAT AND MIXED BINARY SOLVENTS

The solvation characteristics of the ground and excited states of a ketocyanine dye were studied by monitoring the solvatochromic absorption and fluorescence bands. Multiple linear regression analysis indicates that both non-specific dipolar interaction and specific hydrogen-bonding interaction play an important role in the positions of the absorption and fluorescence maxima in pure solvents. In mixed binary solvents, the solute is preferentially solvated. The preferential solvation characteristics of the excited state are determined predominantly by the hydrogen-bond donating nature of the two solvents, while the preferential solvation of the ground state is determined by both dipolar and hydrogen-bonding interactions. In mixed aqueous solvents, the solute acts as a 'probe' for studying the 'microheterogeneity' of the mixture.