Regioselective phenylene-fusion reactions of Ni(II)-porphyrins controlled by an electron-withdrawing: Meso -substituent

Abstract

Oxidation of 10, 15, 20-triaryl Ni(ii)-porphyrins bearing an electron-withdrawing substituent at the 5-position with DDQ and FeCl3 gave 10, 12- and 18, 20-doubly phenylene-fused Ni(ii)-porphyrins regioselectively. A doubly phenylene-fused meso-chloro porphyrin thus prepared was reductively coupled to give a meso-meso linked dimer, which was further converted to a quadruply phenylene-fused meso-meso, β-β, β-β triply linked Zn(ii)-diporphyrin via inner-metal exchange followed by oxidation with DDQ and Sc(OTf)3. As compared to the usual meso-meso, β-β, β-β triply linked Zn(ii)-diporphyrin, this π-extended porphyrin dyad exhibits a smaller HOMO-LUMO gap and a larger two-photon absorption cross-section.