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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).

New ethynyl derivatives were synthesized from 5-(benzothiazol-2-yl)-1-(4-iodophenyl)-3-phenyl-6-vinyl(phenyl)verdazyls using Sonogashira cross-coupling reactions carried out in two stages. The resulted radicals were characterized using EPR, IR, UV/Vis spectroscopy, mass spectrometry, and cyclic voltammetry. Electronic structure calculations using quantum chemistry methods were performed to analyze some experimental results.

The main advances in the synthesis and studies of the properties of new stable heterocyclic verdazyl radicals and verdazyl radical coordination chemistry are reviewed. The promising applications of these radicals are also discussed.

A sequence of alkylation, cyclization, and oxidation reactions was used to convert 5-aryl-1-(benzo[d]thiazol-2-yl)-3-phenylformazans into 6-alkyl-5-aryl-1-(benzo[d]thiazol-2-yl)-3-phenylverdazyls and 5-aryl-1-(benzo[d]thiazol-2-yl)-3-phenyl-6-vinylverdazyls. The paramagnetic and electrochemical properties of the obtained compounds were studied.

Reactions of quinoxalines and quinoxalin-2-ones with C-nucleophiles under acid-catalysis conditions gave products from nucleophilic substitution of hydrogen. Substitution of F atoms in the aromatic core of quinoxalines was studied. Antibacterial and fungistatic activity of the synthesized compounds was studied.