Hedjazi M. Aggregation of organic dyes during formation of ion association complexes with counter-ions of different nature and its use in analysis.

The thesis is devoted to the study of the reactions of the formation of specific ion-associative complexes (IA) between organic dyes and counterions of various natures, as well as their use in chemical analysis. For the first time, the dissertation provides theoretical and experimental explanations of the analytical effects observed during the formation of such IAs within the framework of the exciton theory using the aggregation phenomenon. The conditions for the formation of specific IAs, the principles of the choice of dye, and the analytical form are shown. The investigated reactions were used in the development of simple, express, highly sensitive, and selective reactions for the determination of a number of inorganic and organic substances. In the first chapter, information on those reactions of the formation of ionic associates, which presumably belong to the type considered in this work and are accompanied by characteristic analytical effects, is considered. The reasons that cause changes in the absorption and emission spectra during the formation of IA are discussed, including the influence of IA formation on protolytic equilibria, the formation of charge transfer complexes, and hydrophobic interactions, including the processes of aggregation of dye ions. The general characteristics of the aggregation phenomenon are given, as well as the fundamentals of the exciton theory. The second chapter contains information on the used organic dyes and reagents, devices and equipment, and methods of quantum chemical calculations. The third chapter presents the results of the study of the formation of specific IAs between iodide complexes of bismuth(III), cadmium(II), and mercury(II) with polymethine, rhodamine, and triphenylmethane dyes. Simple, rapid, highly sensitive, and selective spectrophotometric and flow-injection methods for the determination of bismuth(III), cadmium(II), and mercury(II) using their iodide complexes with Astra Phloxine and rhodamine dyes have been developed. It was found that for the correct quantum-chemical modeling of the spectrum of the polymethine dye Astra Phloxine, it is necessary to calculate by the TD-DFT method the vibrationally resolved spectrum using the Frank-Condon principle. A new method of measuring the signal of the scattered light signal was found, which consists in measuring in the luminescence mode (rather than synchronous scanning) when excited by a wavelength that is in the region where the luminescence of the dye is not excited. The detection limit for Bi(III) was 1 μg L-1 (5×10-9 M). The fourth chapter is a continuation of previously performed studies of the interaction of molybdenum heteropoly anions of phosphorus(V) and silicon(IV) with cationic dyes. These reactions were first interpreted within the framework of the exciton theory. It is shown that any representative of cationic dyes is capable of forming specific IAs. The interfering influence, including the mutual influence of phosphate and silicate, was studied in detail, which was the basis of the methods of simultaneous spectrophotometric and sequential injection determination of these substances. The fifth chapter presents the results of the research for new analytical systems, where the dye aggregation reaction plays a decisive role. Organic compounds that contain a nitrogen atom capable of protonation under certain conditions form poorly soluble ionic associates with dyes of the fluorescein series. As an example of such reactions, the interaction of drotaverine, which contains a secondary amino group and erythrosine, was studied. It is shown, including by calculation methods that typical changes in the absorption spectra occur as a result of the reaction. The sixth chapter contains developed methods of analysis of several real objects. The reaction of the formation of IA between tetraiodobismuthate and Astra Phloxine was used for the analysis of drugs and alloys. A similar reaction of the iodide complex of cadmium(II) with Astra Phloxine was used in the development of methods for its determination in mine waters and alloys. Highly sensitive and selective methods for the simultaneous determination of orthophosphate and silicate were used for the analysis of steels, high-purity reagents, and natural waters. The accuracy of the methods for determining drotaverine and mebeverine was shown in the analysis of a number of medicinal products.