N-t-Butyl-α-aryl Nitrones as Potent Spin Traps: DFT Analysis of Electron Localization Function Topology, Local Selectivity, Reactivity and Solvent Effects

Abstract

Density functional theory studies were performed to analyze the reactivity and selectivity of radical capture by N-t-butyl-α-aryl nitrones. Biologically relevant three important radicals viz. hydroxyl, methyl and hydroperoxyl were selected for the study. Topological analysis of the electron localization function (ELF) allows to classify these nitrones as zwitter-ionic type three atom components (TAC). Effects of electron withdrawing and electron donating C-aryl substituents on the electronic chemical potentials, global hardness, electrophilic and nucleophilic indices of nitrones were observed. Radical attack at the carbon atom was predicted by Merz-Kollman algorithm, which is in agreement with the experiments unlike the natural population analysis. Hydroxyl adducts were predicted to be more stable than methyl and hydroperoxyl adducts. cis-Adducts were more stable than the trans-, with the highest differences in stability noted for the methyl adducts. Relative energies of adducts was lowered in non-polar solvents and thus increase in stability was observed along the series from water to heptane.