| Affiliation: | (1) State Key Laboratory of Bioreactor Engineering, Department of Pharmaceutical Sciences, School of Pharmacy, East China University of Science and Technology, Shanghai, 200237, People’s Republic of China;(2) Department of Chemistry, Nankai University, Tianjin, 300071, People’s Republic of China;(3) National Key Laboratory of Micro/Nano Fabrication Technology, Research Institute of Micro/Nano Science and Technology, Shanghai Jiao Tong University, Shanghai, 200240, People’s Republic of China; |
| Abstract: | It has long been known that imidazole can enhance the catalytic activity of catalase model compounds; however, the role of imidazole is still not well understood. In an attempt to elucidate the role of imidazole in promoting the disproportionation of hydrogen peroxide by model compounds, four mononuclear manganese salen (Mn-Salen) complexes with and without axial imidazole ligands were synthesized and characterized by single-crystal X-ray diffraction, UV–vis spectroscopy, electrochemical and HPLC measurements. By comparing the Mn-Salen compounds with and without imidazole ligands, we demonstrated that the activity enhancement of imidazole originated from coordination of imidazole to the manganese center when less than one equivalent of imidazole was present, and from assisted deprotonation of the substrate when excess imidazole was present. These results provide direct evidence for the mechanism of activity enhancement of imidazole in the catalysis of enzyme model compounds. |
