d-Orbital Reconstructions Forced by Double Bow-Shaped Deformations and Second Coordination Sphere Effects of Cu(II) Heme Analogs in HER** |
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| Authors: | Dr. Qiuhua Liu Wanjie Ren Siwei Zhang Dr. Yang Huang Dilong Chen Dr. Wennan Zeng Prof. Dr. Zaichun Zhou Prof. Dr. Lin He Prof. Dr. Wenping Guo Prof. Dr. Jianfeng Li |
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| Affiliation: | 1. Key Laboratory of Theoretical Organic Chemistry and Functional Molecule, Ministry of Education, and School of Chemistry and Chemical Engineering, Institution for Hunan University of Science and Technology, Yuhu District, Xiangtan, 411201 P. R. China;2. College of Materials Science and Optoelectronic Technology, University of Chinese Academy of Sciences, Yanqi Lake, Huairou District, Beijing, 101408 P. R. China;3. State Key Laboratory for Oxo Synthesis and Selective Oxidation, Suzhou Research Institute of LICP, Institution for Lanzhou Institute of Chemical Physics (LICP), Chinese Academy of Sciences, Lanzhou, 730000 P. R. China;4. National Energy Center for Coal to Clean Fuels, Synfuels China Company Ltd, Huairou District, Beijing, 101400 P. R. China |
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| Abstract: | Both geometric architecture and electronic configurations of heme proteins contribute to its activity. In this work we designed and synthesized a series of four copper(II) porphyrin complexes ( 4 -, 3 -, 2 - and 1 -Cu) where the molecular conformations are modulated by a pair of stepwise shortened straps on the same porphyrin side (cis-ortho) to give double bow-shaped skeletons. Single crystal structures demonstrate that the straps gradually increase the saddle deformation and the deviation of the metal centers, which is in accordance with two, unusual d-orbital reconstructions of two different ground states, as revealed by 4 K EPR and DFT calculations. In the study of the electrocatalytic hydrogen evolution reaction (HER), 1 -Cu, with the shortest straps, showed the most apparent improvement of activity. Second coordination sphere (SCS) effects created by the double bow-shaped architecture and the strong saddle porphyrin core in 1 -Cu are found to play key roles in proton trapping during the catalytic process. The work contributes a novel strategy to improve the catalytic performance of heme analogs through ligand geometric modulation. |
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| Keywords: | d-orbital reconstruction heme analogs HER metalloporphyrins second coordination sphere effect |
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