Partial and full beta-bromination of meso-tetraphenylporphyrin: Effects on the catalytic activity of the manganese and nickel complexes for photo oxidation of styrene in the presence of molecular oxygen and visible light

摘要

A series of beta-brominated meso-tetraphenylporphyrins, H2TPPBrx (x = 0, 4, 8) have been synthesized and the photocatalytic activity of their manganese (III) and nickel (II) complexes in photo oxidation of styrene was thoroughly investigated. The green photo oxidation process was done using molecular oxygen and in the presence of visible light. The effect of solvent and bromination degree was studied on the catalytic activity and stability of sensitizers. Based on the obtained results, free base porphyrins showed better catalytic activity among metallated counterparts and the order of catalytic activity was as follows: H2TPPBr4>H2TPPBr8 >H2TPP. The order for Ni and Mn metallated porphyrins was also obtained as: NiTPPBr8 >NiTPPBr4 >NiTPP and MnTPPBr4(OAc)>MnTPP(OAc) MnTPPBr8(OAc), respectively. According to the stability studies, significant increase was observed after addition of metal in porphyrin structure; i.e. more than 80% in the case of Ni. Finally, a mechanism was proposed for photo oxidation of styrene in the presence of H2TPP porphyrin. (c) 2020 Elsevier B.V. All rights reserved.