Carbon‐ and SO2‐Locked Diarylnitroxides: Quantum Chemical Consideration, Synthesis, and Electrochemistry

Abstract

Selection of linkers connecting two phenyl rings as a part of molecular design of diarylnitroxides with increased kinetic stability of redox forms was performed using quantum chemical estimation of the geometry and oxidation potential values. It revealed that introduction of the carbon bridge cannot be considered as efficient “instrument” for structural tuning of the nitroxide properties since altering neither the length of the bridge nor its position results in significant changes in the oxidation potential, in contrast to a heteroatomic bridge, which makes more perturbation in the electronic structure of diarylnitroxide. To support the prediction, new SO2‐bridged diarylnitroxide was synthesized and characterized using spectral and electrochemical methods. It is extremely stable in benzene solution, exhibits the maximal anodic potential value achieved for reversibly oxidized nitroxides to date (1.33 V, Ag/AgCl/KCl) and seems promising as cathodic redox active material providing maximal potential gap as compared to the previously reported compounds.