Electrochemically Driven Intramolecular Oxidative Aromatic Coupling as a Pathway toward π-Extended Porphyrins

A Ni(II) complex of a π-extended porphyrin bearing three mesityl substituents and one electron-rich naphthalene moiety has been prepared via electrochemical oxidation. It was proven that the whole oxidative process starts from electrochemical generation of a radical-cation on the porphyrin core. Electrochemistry and spectroelectrochemistry of both a naphthalenyl-substituted porphyrin and a porphyrin with a fused naphthalenyl group on the π-ring system provide clear distinction between metal- and ring-centered processes. The redox reactivity of the naphthalenyl-substituted metalloporphyrin in nonaqueous media is presented while outlining the most important structural factors which influence the reversible half-wave potentials for oxidation and reduction of this complex and the following chemical reactions which lead to an extended π-system.