Regioselective Oxidative Ring Cleavage of Antiaromatic Nickel(II) Norcorrole to Dialkoxybis(dipyrrin)s

The Ni(II) complex of meso-dimesitylnorcorrole is a stable 16π antiaromatic porphyrinoid. We have previously reported that the reaction of the norcorrole Ni(II) complex with m-chloroperbenzoic acid resulted in oxygen insertion to afford the corresponding 10- oxacorrole Ni(II) complex, which is an 18π aromatic porphyrinoid. In sharp contrast, we have found that treatment of the norcorrole Ni(II) complex with bis[(trifluoroacetoxy)iodo]benzene in the presence of a variety of alcohols induced a ring-opening reaction to furnish the corresponding dialkoxybis(dipyrrin)s through regioselective oxidative C-C bond cleavage. Furthermore, dihydroxybis(dipyrrin) exhibited solvent-dependent absorption and emission behavior through keto-enol tautomerization of the hydroxy groups.