Ambipolar diarylnitroxides: Molecular design and electrochemical testing

Possible approaches to molecular design of stable diarylnitroxyl radicals capable to form sufficiently stable cations and anions under one-electron oxidation and reduction are discussed. Both covalent and noncovalent stabilizing “tools” are considered. The main focus is made on the dynamic stabilization of oppositely charged redox states of a molecule through conformational changes. The efficiency of the approaches was confirmed on a wide range of novel diarylnitroxides designed accordingly to the suggested guidelines. Spectral and quantum-chemical data support fast conformational changes accompanying electron transfer steps and facilitating stabilization of the cationic and anionic species. Voltammetric study of new compounds revealed the formation of reversible redox couples in both anodic and cathodic areas for the majority of nitroxides making them suitable for practical application.