Cheipesh T. Fluoresceins in solutions: protolytic equilibria, optical properties and application for calixarenes investigation

The work is devoted to the peculiarities of the influence of solvent and cationic calixarenes aggregates on the absorption and fluorescence spectra, parameters of acid-base equilibria and tautomeric constitution of ethers and esters of fluorescein and 4'- и 5'-aminofluorescein and also the reaction kinetics of related compounds. On the basis of the spectra and protolytic equilibria constants of more simple compounds the tautomeric conversion scheme of the fluorescein was confirmed and applied to the tetrabasic dyes - aminofluorescein isomers. For the last-named, the formation of additional tautomers was detected, that is due to the presence of the amino group on the phthalic moiety. The assembling of the hydrogen bonds on the carboxylate group, as well as protonation, appeared to play a critical role in process of intra-molecular fluorescence quenching of aminofluorescein dianions. This is expressed as the fluorescence increasing of the dianions in non-hydrogen bond donor solvents. The influence of the aggregates of calixarenes bearing alkyl groups of different lengths on the fluorescence intensity and the rate of reactions of dyes with hydroxide ion form the basis of the complex of the indicative processes, that allow to distinguish the aggregates and surfactant micelles, whereas the acid-base equilibria shift, as well as changes of the absorption spectra, reveals the similarity of these systems.