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X-ray emission spectra of oxygen OK α and X-ray photoelectron O1s spectra are obtained for stable nitroxyl radicals: 3-imidazoline derivatives and their diamagnetic derivatives. It is shown that the highest occupied molecular orbitals in the nitroxyl radicals mainly consist of oxygen and nitrogen 2p atomic orbitals of the nitroxyl group. Distinctions in the X-ray emission spectra of oxygen of the compounds studied can be due to the presence of the unpaired electron in the radicals.

Spin-labeled α-tocopherol succinyl derivatives were synthesized by the reaction of α-tocopherol succinate with 4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl, 3-aminomethyl-2,2,5,5-tetramethylpyrrolidine-1-oxyl, and 3-amino-2,2,5,5-tetramethylpyrrolidine-1-oxyl. Acylation of spin-labeled trolox amides by succinic anhydride produced the corresponding spin-labeled trolox amide succinyl derivatives.

Spin-labeled cytisine derivatives containing stable pyrrolidine and piperidine nitroxyl radicals were synthesized by acylation and alkylation of the secondary amine. Toxicological studies showed that introduction of the nitroxyl group decreased significantly the general toxicity.

Electrochemical oxidation of 2H-imidazole N-oxides was studied using cyclic voltammetry and ESR spectroscopy. The formation of the 2,2-dimethyl-4,5-diphenyl-2H-imidazole 1,3-dioxide radical cation was noticed for the first time. The possibility of reaction between the 2H-imidazole N,N-dioxide radical cation and methanol including the detachment of a hydrogen atom from the MeOH methyl group was demonstrated.

The spin-spin coupling constants 3JC,H between the hydrogen atom of the aldonitrone group and the carbon atom bound to the nitrogen atom of the N-oxide fragment were determined for a wide range of cyclic and acyclic aldonitrones. Based on comparison of these constants (trans-3JC,H (E isomer) > cis-3JC,H (Z isomer)), the Z configuration was assigned to acyclic nitrones. Coordination of organolithium compounds to the oxygen atom of the N→O group was revealed by 13C NMR spectroscopy. This coordination is the necessary condition for the metallation of aldonitrones. The configuration of the nitrone group is responsible for the ability of the E form of acyclic aldonitrones to undergo CD3ONa-catalyzed isotope exchange of the methine proton in CD3OD and metallation with BusLi.

The reactions of cyclic aldo- and α-methoxynitrones of the 2H-imidazole-1-oxide and 4H-imidazole 3-oxide series with isocyanates, phenyl isothiocyanate, N-phenylmaleimide, and dimethyl acetylenedicarboxylate were studied. The reactions give the corresponding 1,3-dipolar cycloaddition products. 2,2-Dimethyl-4-phenyl-2H-imidazole 1-oxide does not enter into a similar reaction with isocyanates or phenyl isothiocyanate.

The formation of charge transfer complexes between chlorine dioxide and nitroxyl radicals (2,2,6,6-tetramethylpiperidin-1-oxyl, 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl, 4-oxo-2,2,6,6-tetramethylpiperidin-1-oxyl, 4-methoxy-2,2,6,6-tetramethylpiperidin-1-oxyl, 4-acetylamido-2,2,6,6-tetramethylpiperidin-1-oxyl, 2,2,5,5-tetramethyl-4-phenyl-3-imidazolin-1-oxyl, and bis(4-methoxyphenyl) nitroxide) in acetone, acetonitrile, n-heptane, diethyl ether, carbon tetrachloride, toluene, and dichloromethane was found by spectrophotometry at –60—+20 °C. The thermodynamic parameters of complex formation were determined. The radical structure affects its complex formation ability. The charge transfer complex is transformed into the corresponding oxoammonium salt.