SPECTROSCOPY OF A NON-LUMINESCENT ASSOCIATE OF INDIGO CARMINE IN SOLUTIONS

Introduction. The food dye Indigo Carmine (E-132) was subjected to spectroscopic studies. It is shown that conditions for their participation in Association processes are created in aqueous and binary mixtures of solvents. The absorption bands against the background of the hypochromic effect in their electronic spectra are determined. Experimentally and by quantum chemical calculations, it is established that the dipole moments of the Indigo Carmine dye in the excited state increase up to 40 % and they contribute to the appearance of a strong dipole-dipole interaction, which results in the unification of Monomeric molecules into an associate. The interaction force (van der Waals) leads to resonant splitting of electronic States and changes in the probability of electron transition from the main excited levels of dye molecules. Research methods. The choice of binary mixtures of solvents was due to the fact that in one of the components of the solvents the dyes under study dissolved well, in the other they practically did not dissolve. Electronic absorption spectra were recorded on a Specord 50 SA spectrophotometer (Analytikjena Germany), the optical density was measured with an accuracy of 0.3% and high resolution in the range of 190-1100nm. Microscopic studies were carried out on a biological microscope KSO 5001-1 Anjeon presicion optics Co, Htd (South Korea) and on an electron microscope (SEM) TESCAN Mira3 (Russia). The fluorescence spectra were measured using a setup based on two MDR-76 monochromators with photoelectronic recording. Quantum-chemical calculation of the electronic structure and distribution of charges on the atoms of Indigo Carmine molecules was carried out using the MOPAC 2009 software package by the AM1 semiempirical method with a standard set of parameters Results and discussions. It has been shown experimentally that an increase in the concentration of the dye in solutions with a constant ratio of binary mixtures water + dioxane is accompanied by a drop in their integral absorption capacity. The long-standing increase in the concentration of the investigated compound leads to an increase in the process of falling of the electronic spectra of the solution, with a hypochromic effect observed, similar to that of an aqueous solution of a dye. Based on calculations, it was shown that for Indigo Carmine, the angle 88,960 i.e. close to 900. The diagram of the arrangement of molecules in associates of the dye Indigo Carmine can be attached as parallel vectors. Conclusion. It is shown that an increase in the concentration of food dye in aqueous and binary mixtures of a solvent creates conditions for the association of Indigo Carmine identifying hidden bands of associated molecules. It is proved that the observed hypochromic effect during the association of Indigo Carmine molecules is due to resonant splitting of excited electronic levels under the action of the field forces of closely spaced food dye molecules. It was found that the ratio of the energy of the dipole-dipole interaction in the associate, “∆E”, to the width of the Frank-Kondo electronic transition “∆ε” has the ratio ∆E / ∆ε\u3e 1