Facile Synthesis of β‐Brominated Manganese Porphyrins and their Catalytic Potentials for Haloperoxidases‐Like Activity

Abstract

AbstractA novel and sustainable approach has been developed for the synthesis of β‐brominated Mn porphyrins, [MnIII(Br)(TPPBr4)] (2), [MnIII(Br)(TPPBr6)] (3) and [MnIV(Br)2(TPPBr8)] (4) by self catalytic haloperoxidase mimicking activity of [MnIII(Br)(TPP)] [bromo(meso‐tetraphenylporphyrinato)manganese(III)] (1) in aqueous medium under different mild and controlled reaction conditions. By precisely tweaking important parameters (e. g. H2O2, HClO4 and KBr), these polybrominated porphyrin complexes have been synthesized. This method is safer and applicable under milder reaction conditions than the conventional procedures for β‐bromination of porphyrins. These complexes were characterized by various spectroscopic techniques, including UV–Vis spectroscopy, elemental analysis, MALDI‐TOF mass spectrometry, cyclic voltammetry, DFT calculations and single crystal X‐ray diffraction analysis. Bromination of various phenol derivatives via haloperoxidase‐catalyzed reaction using these manganese complexes has been explored. Carrying out the catalytic reaction at room temperature in the presence of H2O2 as an oxidant and KBr as a brominating agent in a mild aqueous acidic condition results in good to excellent yield of the brominated product(s). Extra stability of 4 compared to other catalysts due to trans‐[Br−MnIV−Br] structure possibly prevents the interaction of Mn with oxidant which makes it less potential catalyst compared to 1, 2 and 3. Suitable catalytic reaction mechanism has been proposed for the bromination of substrates after identifying the reaction intermediates using mass spectrometry.