Nature-Inspired Redox Active Organic Molecules: Design, Synthesis, and Characterization of Pyridine Derivatives

In this article, we present experimental and theoretical studies of pyridine derivatives (pyDs) inspired by natural systems to investigate the electron transfer processes occurring in aqueous media and elaborate a theoretical model that adequately predicts the behavior of new derivatives. Our results might be relevant to scientific and technological applications, including energy storage, redox-active scaffolds for organic synthesis, photoredox catalysis, and new materials. The synthesis of eight pyDs is reported. To improve water solubility, six new compounds are hexafluorophosphate alkylammonium salts. The pyDs exhibit irreversible redox processes, with electron-donating substituents decreasing the cathodic peak potential while electron-withdrawing groups increase it; when both substituents are present, the latter effect prevails. A computational study was performed to investigate the electrochemical behavior of the synthesized compounds and design new electroactive pyDs. DFT calculations provided the predominant species’ redox potentials and acidity constants to elaborate Pourbaix diagrams for each compound. The synthesized molecules exhibit a two-electron-one-proton dismutation process in the water pH window. Beyond this range, stabilized radical species undergo one-electron exchange processes. We correlated experimental and calculated parameters, screening 22 additional derivatives to evaluate their electrochemical behavior, identifying potential candidates capable of performing a one-electron transfer process in the pH window of water, revealing new applications for pyDs.