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The results of studying electrochemical conversions of 7-R-3-X-1,2,4-triazolo[5,1-c][1,2,4]-triazin-4-ones (Triazavirin® and its derivatives) using cyclic voltammetry, chronoamperometry, and ESR spectroscopy are presented. The derivatives of 7-R-3-X-1,2,4-triazolo[5,1-c][1,2,4]-triazin-4-ones were found to be capable of electrochemical reducing in the potential range from −0.16 to −0.68 V (vs Ag/AgCl) in a Britton—Robinson buffer at pH 2–12. At the potentials of the first electroreduction step at pH 2–6, the main process of transformations is the four-electron scheme of reduction of the nitro group of Triazavirin®. The adduct of the radical substances with the spin probe N-(1-hydroxy-2,2,6,6-tetramethylpiperidin-4-yl)-2-methylpropanamide was registered after the preliminary generation of the Triazavirin® radical anion at −0.5 V vs Ag/AgCl in an acidic medium. A linear dependence of the current of the first electroreduction step of the Triazavirin® on the concentration was obtained at pH 2 (linearity range from 10−4 to 1.6 · 10−2 mol L−1, I = −1.93 · C, R2 = 0.9977).

A convenient transition-metal-free approach, based on nucleophilic substitution of hydrogen (SNH), for consecutive regioselective C–H functionalization of 1,3,7-triazapyrene scaffolds with carboranyllithium and phenyllithium is reported. The theoretical calculations disclosed highlight key features in the regioselectivity and mechanism of the investigated SNH transformations. The novel 1,3,7-triazapyrene-based ortho-carboranes obtained have large potential in the field of molecular electronics as organic luminophores, which are characterized by the aggregation-induced emission and dual-emission effects.

In this work, the surface of the platinum disk electrode was modified with p–aminobenzoic acid by the method of oxidative electrografting (OEG) and the mechanism was proposed. The density of carboxyl groups immobilized in this way was estimated using differential pulse voltammetry. In addition, the effect of preliminary modification of the electrode surface by carboxylated carbon nanotubes (c–MWCNTs) on the density of carboxyl groups was studied. Modification allowed consequently improving the analytical characteristics of the working electrode.

Kinetic features of the reactions of K4[Fe(CN)6] with radicals initiated by water-soluble azo-initiator 2,2′-azobis(2-amidinopropane) dihydrochloride (AAPH) at 37 °C were studied using the potentiometric method. Potassium ferrocyanide was shown to be a radical acceptor, whereas K3[Fe(CN)6] formed by the oxidation with the radicals in combination with K4[Fe(CN)6] is an electrochemical system, the study of which makes it possible to determine kinetic characteristics of radical reactions. The rate constants for the reactions of peroxide radicals RO2 · with K4[Fe(CN)6] were calculated.

We present the results of synthesis and study of the electrocatalytic activity of gold and silver nanoparticles of different composition (individual metals, core–shell particles, nanoalloys, and particles synthesized electrochemically), immobilized on the surface of a glassy carbon electrode, with respect to cholesterol. A surfactant (cetyltrimethylammonium bromide) is selected to create an aqueous–organic emulsion of cholesterol. It is demonstrated that nanoparticles with a gold core and a silver shell with the regression equation of I = 1.4 × 10–5 c chol + 5.8 × 10–5 (R 2 = 0.97) and silver nanoparticles synthesized electrochemically with the regression equation of I = 1.0 × 10–5 c chol + 3.0 × 10–4 (R 2 = 0.95) possess optimal electrocatalytic characteristics.

The determination of cholesterol concentration in the blood is an important characteristic of the state of health. Modern methods for the detection of cholesterol involve the use of enzymes or expensive and complicated equipment. In this study, an enzymeless electrochemical method for the quantitative determination of cholesterol using cobalt (II) chloride as an electrocatalyst has been proposed. An analytical signal was peak current of cobalt (II) chloride faradaic oxidation on a platinum disk electrode in acetonitrile media in the presence of cholesterol via linear sweep voltammetry. A possible path of the electrocatalytic oxidation of cholesterol on the electrode surface was proposed. The catalytic constant kcat and the Michaelis constant Km calculated for the electrocatalytic oxidation process of cholesterol on the electrode surface are comparable in magnitude to the natural enzyme cholesterol oxidase, indicating the high efficiency of CoCl2 as an electrocatalyst for oxidation and, therefore, the determination of cholesterol. The highest value and the best reproducibility of analytical signal are reached at a CoCl2 concentration of 25 mM and a scan rate of 100 mV·s− 1. The linear region of the calibration curve “current-cholesterol concentration” obtained using a developed method in a solution of 0.1 M LiClO4 and 25 mM CoCl2 in acetonitrile is 25–200 μM (R2 = 0.971) with a detection limit of 2 μM.

Peculiarities of electrochemical behavior of the Fe3O4 magnetic nanoparticles immobilized on the surface of a platinum electrode in aprotic organic media were investigated. Possible scheme of electrochemical behavior of nanoparticles depending on pre-electrolysis potential (–1.3,–2.5 V) was suggested. The effect of pre-electrolysis time, potential scan rate and nature of supporting electrolyte on the processes investigated was determined. A linear dependence of electrochemical oxidation signal versus the concentration of nanoparticles in modifying suspension in the concentration range of 0.05—0.5 g L–1 was observed. The results of the performed research allow using magnetite nanoparticles as a direct signal-generating label in electrochemical immunoassay.

A potentiometric method was proposed for the determination of rate constants for peroxyl radical generation using the reduced form of the metal in the complex. The kinetics of the thermal decomposition of 2,2′-azobis(2-methylpropionamidine)dihydrochloride was studied. The requirements for an electron donor (reactant) were formulated. The iron(ii) complex with EDTA, the iron(ii) complex with o-phenanthroline, and potassium hexacyanoferrate(ii) were used as reactants. The rate for peroxyl radical generation and the generation rate constant (the latter turned out to be (0.92±0.06)•10–6 s–1) were calculated. The studies were carried out for different temperatures and concentrations of the initiator and complex.

To study acidity of polyfluorosalicylic acids, their ionization constants (pKa) were determined. A series of metal salts and heteroligand complexes was obtained from polyfluorosalicylic acids containing biogenic metal ions and coligands, such as triphenylphosphine, pyridine, 2,2′-bipyridine and 1,10-phenanthroline. The structures of synthesized salts and complexes were determined by elemental analysis, HRMS and IR spectroscopy. X-Ray diffraction analysis was used to confirm the structure of the heteroligand metal complexes based on polyfluorosalicyic acids and bipyridine-type coligands. In the heteroligand complexes, it was possible to achieve different ratios of polyfluorosalicylate and coligand, depending on the metal cation. The antimycotic and antibacterial activities of polyfluorosalicylic acids were studied and their metal complexes were investigated. The metal heteroligand complexes were found to exhibit high anti-gonorrhea activity. In addition, cobalt(II) 2,3,4,5-tetrafluorosalicylato-κ2O-bis(2,2′-bipyridine-κ2N) dihydrate was found to show a pronounced activity against Trichophyton rubrum, T. interdigitale, Epidermophyton floccosum strains.

Methods are developed for the non-enzymatic chronoamperometric determination of urea in blood serum and creatinine in model solutions imitating the composition of blood serum. The selectivity of determination is ensured using columns packed with an anion-exchange resin for urea or synthesized molecularly imprinted polymers for creatinine.

The organic nickel(ii) complexes with catalytic activity in the electrochemical oxidation of creatinine and urea were synthesized and studied. The signals of electrocatalytic oxidation of the studied carbonyl-containing amines in model solutions were obtained. The detection limit (by the 3σ-criterion) is 8.7·10−6 and 2.7·10−5 mol L−1 for urea and creatinine, respectively.