ELECTROCHEMICAL INVESTIGATIONS OF THE INTERACTION OF CAFFEINIUM COMPOUNDS WITH POLYANІОNES OF Мо AND W WITH OF 1,3,5 - TRIPHENYL VERDAZYL RADICAL

Abstract

The work continues the study on the peculiarities of the interaction of 1,3,7-trimethylxanthine (caffeine) compounds with polyoxometalates of molybdenum and tungsten with the artificial radical of 1,3,5- triphenylverdazyl (TFV). Using the example of a model reaction with the TFV radical, these compounds showed a special antiradical action. Based on the research results, it was found that the nature of the destruction of the radical when interacting with (HСaf)3[PМ12O40]∙6H2O (where М = Мо, W) differs from most known systems, which are characterized by a mechanism of disproportionation. The data obtained confirmed the previously made assumption about the chemical nature of these interactions. To establish the stoichiometry of the reaction between TFV and (HСaf)3[PW12O40], electrochemical studies were conducted which showed that the activity of the radical is restored after exceeding the concentration ratio of 12 : 1, respectively. The synergism of the components of the compound (HСaf)3[PW12O40] is shown: when TFV interacts with H3[PW12O40], the maximum cathode current characteristic of TFV occurs at a concentration ratio of 4 : 1, respectively, while caffeine has no antiradical effect at all. Previously obtained data from X-ray diffraction analysis of compounds (HСaf)3[PMo12O40]∙6H2O, (HСaf)3[PW12O40]∙6H2O prove that the orientation of protonated caffeine relative to polyoxamethalate-anion is possible due to hydrogen bonds =O…H–N=. This process can result in the delocalization of the charge over the entire O-enriched surface, by all twelve groups [О–Ме–О]-, which are part of the POM, making the latter active centers capable of interacting with TFV.
 Therefore, the data presented correlate with the previously obtained results of spectrophotometric analysis and X-ray diffraction data and confirm the previously made conclusions.