Bioinspired metalloporphyrin derivative can catalyze various types of multielectron redox reactions under physiological conditions such as detoxification of reactive oxygen species and water oxidation. Thus, metalloporphyrin derivative has application potential in wide field of chemistry. However, the derivatization for catalysis often requires multi-step synthesis and results in water-insolubility or lack of diversity in catalytic reactions. We have focused on supramolecular approach for metalloporphyrin derivative as a multicatalyst. Cucurbit[n]uril (n=6,10) is known for encapsulating a cationic porphyrin derivative (5,10,15,20-tetrakis (N-methylpyridinium-4-yl) porphyrin (H2M4Py4P) ). We have hypothesized that ease of constructing a ternary structure in CB[10] cavity allow multiple catalytic reaction in aqueous media. Herein, we report enhanced catalytic H2O2 disproportionation (2H2O2 → 2H2O + O2) of Mn-porphyrin derivative by supramolecular system composed of Mn(III)-5,10,15,20-tetrakis (1,3-dimethylimidazolium) porphyrin (MndMIm4P), CB[10] and imidazole (Im). H2O2 disproportionation is crucial to reduce oxidative damage in the field of medicinal chemistry. Also, MndMIm4P and its cobalt analogue are known as potent catalyst for water oxidation. Therefore, our study would provide an important insight into multielectron redox catalyst in the field of energy chemistry as well as medicinal chemistry. Encapsulation of MndMIm4P in CB[10] was monitored by 1H NMR measurement using ZndMIm4P as a model complex. Interestingly, the proposed binding mode for ZndMIm4P/CB[10] is different from that of ZnM4Py4P/CB[10] previously reported. We speculate that molecular size of metallo porphyrins depends on encapsulation mode with CB[10]. 1H NMR titration suggests that 3 equivalents of Im can be encapsulated in residual space of ZndMIm4P/CB[10]. Axial coordination and charge transfer interaction are the driving force for the encapsulation. H2O2 disproportionation activity of the resulting MndMIm4P/CB[10]/Im was significantly higher than MndMIm4P alone. This result is important from technological point of view because the enhanced activity was achieved by simply mixing the components in water. Furthermore, CB[10] suppressed peroxidase activity of MndMIm4P, which is toxic side reaction. Thus, MndMIm4P/CB[10]/Im can be a new approach for therapeutic antioxidant. Antioxidative activity of MndMIm4P/CB[10]/Im in in vitro will be reported in presentation.

Novel supramolecular approach for multicatalytic activity of Mn-porphyrin derivative

254th National Meeting (2017)

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