Synthesis of conjugated Mn porphyrin polymers with p-phenylenediamine building blocks and efficient aerobic catalytic oxidation of alcohols

Abstract

A series of conjugated metalloporphyrin polymers (MnP-AMPs) were synthesized based on Buchwald-Hartwig aromatic amination with p-phenylenediamine and manganese tetraphenylporphyrin as building blocks, and N-heterocyclic carbene-palladium complex as catalyst. Brunauer–Emmett–Teller surface area analysis, scanning electron microscopy and transmission electron microscopy showed that MnP-AMPs had large surface areas and uniform pore sizes. The stable porous and superreticular conjugated structure of MnP-AMP further activated manganese ions in the porphin ring compared with those in the original monomanganeseporphyrin. Moreover, introducing CN bonds in MnP-AMP increased its polarity and affinity to alcohols, so MnP-AMP exhibited high catalytic activity when applied to aerobic oxidation of alcohols. For the catalysis of selective oxidation of benzyl alcohol to benzaldehyde with air, the conversion and aldehyde selectivity both reached up to 100% under mild condition in acetonitrile at 40°C. MnP-AMP also remained stable in oxidation reaction system and still had high catalytic activity after several recycles.