SOLVENT EFFECTS ON THE PHOTOPHYSICAL PROPERTIES OF DIBUCAINE: A QUINOLINE ANALOGUE

Abstract— Emission and absorption spectra of neutral, monocation and dication dibucaine were recorded in hydrocarbon and hydroxylic solvents. The spectral analysis indicates that the lowest electronic states of dibucaine originate from the quinoline analogue in the molecule. The fluorescence and phosphorescence emission of neutral dibucaine in all solvents at 77 K are best assigned as resulting from ¹ n ,π* and ³π,π*, respectively, whereas those of both monocation and dication dibucaines are found to have ¹π,π* and ³π,π*. The monocation and neutral dibucaines in ethanol solutions were shown to give identical emission spectral properties, indicating that dibucaine-HCl in ethanol is H⁺ dissociative; this was confirmed by FT-IR studies. The possible explanations for the deprotonation of dibucaine-HCl in ethanol environments are discussed.