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

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.

A divergent strategy for the synthesis of redox-active verdazyl radical polymers

We describe a divergent synthetic strategy based on ATRP and CuAAC chemistry for the production of stable radical polymers. As a proof of concept, we prepare verdazyl radical polymers with properties suitable for use in organic electronics.

An oxo-verdazyl radical for a symmetrical non-aqueous redox flow battery

Verdazyl free radical compounds are promising candidates for symmetrical all-organic redox flow batteries (RFBs) due to their redox stability, the ease with which their chemical structure can be varied, and their unique bipolar nature.

Syntheses, spectroscopy, and crystal structures of 3-(4-bromophenyl)-1,5-diphenylformazan and the 3-(4-bromophenyl)-1,5-diphenylverdazyl radical and the crystal structure of the by-product 5-anilino-3-(4-bromophenyl)-1-phenyl-1H-1,2,4-triazole

The title compounds, C19H15BrN4, C20H16BrN4and C20H15BrN4, are nitrogen-rich organic compounds that are related by their synthesis. The verdazyl radical, in which stacking leads to antiferromagnetic interactions, was reported previously [Iwaseet al.(2013).Phys. Rev. B,88, 184431]. For this compound, improved structural data and spectroscopic data are presented. The other two compounds have been crystallized for the first time and form stacks of dimers, roughly along thea-axis direction of the crystal. The formazan molecule shows signs of rapid intramolecular H-atom exchange typical for this class of compounds and spectroscopic data are provided in addition to the crystal structure. The triazole compound appears to be a side-product of the verdazyl synthesis.

Ferro- or antiferromagnetism? Heisenberg chains in the crystal structures of verdazyl radicals

Quantum chemically calculated exchange-coupling maps are employed to design verdazyl radical crystals with either ferromagnetic or antiferromagnetic behaviour.

SYNTHESIS OF 1,5-DIPHENYL-3-ARYLVERDAZILS

The reaction between verdazyls and CH-acids was studied for checking common views on the stable radicals reactivity which is usually associated with the spin density values of the reaction centers and its alterations due to the influence of substituents. The synthesis of row l,5-diphenyl-3-arylverdazyls that contains the different types of substituents in the phenyl rings that are situated at C3 verdazyl radical atom was carried out for this purpose. This also includes the previously non-described 1,5-diphenyl-3-(4-hydroxyl)phenyl-, 1,5-diphenyl-3-(4-bromo)phenyl-, 1,5-diphenyl-3-(3- nitro)phenylverdazyls. In this case, the availability and nature of the substituents in the phenyl rings at C3 verdazyl radical atom may not be affected by the change in the spin density values on the N2 and N4 nitrogen atoms that are verdazyl radicals’ reaction centers. The synthesis of verzdazyls was carried out according to the conventional scheme, on the basis of arylhydrazones. It was observed that during azocoupling reacting of phenyldiazonium chloride with arylhydrazones in the synthesis of formazans the reaction proceeds with a higher yield when the solvent dimethylformamide-pyridine is being used. Transformation of formazans into verdazyl radicals was being carried out at room temperature with formaldehyde exposured to formazan in the presence of potassium hydrogen sulfate under the constant air going through the reactor feed. The availability of substituents in the phenyl ring at C3 formazan atom was increasing reaction time significantly in comparison with 1,3,5- trifenylformazan regardless of the substituent’s nature at C3 formazan atom. During the reaction between 1,5-diphenyl-3-arilverdazyls and CH-acids (acetylacetone and dimedone), it was discovered that the reaction rate depends on both the acidity of the CH-acid (dimedone reacts faster than acetylacetone) and the nature of the substituents situated in phenyl ring at C3 verdazyl atom. At the same time, the electron-donating substituents increase the rate of reaction between verdazyls and CH-acids while electron-donor substituents decrease it. Therefore, as it was formerly reported, when we deal with monochloroacetic acid, the rate of a reaction between verdazyl radicals and CH-acids is increasing in front of the electron-donor substituents and decreasing in front of electron-acceptor substituents. These regularities are not connected with the spin density values of the verdazyls’ reaction centers.Forcitation:Tsebulayeva Yu.V., Pryanichnikova M.K., Tanaseichuk B.S. Synthesis of 1,5-diphenyl-3-arylverdazils. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 1. P. 23-29