Electrochemical Synthesis of Pyridinium-Conjugated Assembly based on Nucleophilic Substitution of Pyrene/Perylene π-Radical Cation

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Efficient and selective N-arylation of pyridine derivatives was demonstrated as nucleophilic substitution reaction of electrochemically generated π-radical cations such as pyrene and perylene. 1-Methylimidazole also worked as a nucleophile toward pyrene π-radical cation to give the imidazorium. This reaction provides a widely applicable and powerful method for pyridinium-conjugated assembly in which redox-active pyridinium moieties can be integrated through π-conjugated system. Preparative scale synthesis was demonstrated successfully by using perylene π-radical cation prepared by chemical oxidation with I₂/AgClO₄. The resulting pyridinium-conjugated assembly shows both one-electron reduction assigned to the pyridium moiety and one-electron oxidation of the pyrene and perylene moieties. UV-visible absorption and fluorescence spectra indicated intramolecular charge transfer character from the pyrenyl and perylenyl moieties to the pyridinium ones of the pyridinium-conjugated assembly.