Electrochemical synthesis of pyridinium-conjugated assembly based on nucleophilic substitution of pyrene/perylene π-radical cation

Efficient and selective N-arylation of pyridine derivatives was demonstrated as nucleophilic substitution reaction of electrochemically generated pi-radical cations such as pyrene and perylene. 1-Methylimidazole also worked as a nucleophile toward pyrene pi-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 pi-conjugated system. Preparative scale synthesis was demonstrated successfully by using perylene pi-radical cation prepared by chemical oxidation with I-2/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.