Radical anions of 3,3′-bi(2-R-5,5-dimethyl-4-oxopyrrolinylidene) 1,1′-dioxides in MeCN-H2O solvent mixtures

Abstract

Radical anions of cyclic dinitrones, 3,3′-bi(2-R-5,5-dimethyl-4-oxopyrrolinylidene) 1,1′-dioxides (R = Me, Ph, But, CF3) have been studied by ESR in combination with quantum chemical calculations of geometrical parameters and isotropic hyperfine interaction constants by the DFT/PBE methods in the 3z basis set and UB3LYP in the 6–31+G* basis set with allowance for the solvation in the framework of continual PCM model. The radical anions were generated electrochemically by reduction of their neutral precursors in MeCN-H2O solvent mixtures and found to possess enough stability for measurement of their ESR spectra in a wide range of the mixture compositions. Radical anions of compounds of nitrone series were generated and characterized in MeCN-H2O mixtures and water (for the dinitrone with R = Me) for the first time. Differences in the solvent depending behavior of the nitrogen hyperfine interaction constants in the series of radical anions with various substituents R are explained by competition of transsolvation and structural effects.