中国物理B ›› 2023, Vol. 32 ›› Issue (1): 18201-018201.doi: 10.1088/1674-1056/ac98a5

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Concerted versus stepwise mechanisms of cyclic proton transfer: Experiments, simulations, and current challenges

Yi-Han Cheng(程奕涵)1, Yu-Cheng Zhu(朱禹丞)1, Xin-Zheng Li(李新征)1,2,3,4, and Wei Fang(方为)5,6,†   

  1. 1 State Key Laboratory for Artificial Microstructure and Mesoscopic Physics, Frontier Science Center for Nano-optoelectronics and School of Physics, Peking University, Beijing 100871, China;
    2 Interdisciplinary Institute of Light-Element Quantum Materials and Research Center for Light-Element Advanced Materials, Peking University, Beijing 100871, China;
    3 Peking University Yangtze Delta Institute of Optoelectronics, Nantong 226010, China;
    4 Collaborative Innovation Center of Quantum Matter, Peking University, Beijing 100871, China;
    5 Department of Chemistry, Fudan University, Shanghai 200438, China;
    6 State Key Laboratory of Molecular Reaction Dynamics and Center for Theoretical Computational Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
  • 收稿日期:2022-09-02 修回日期:2022-10-08 接受日期:2022-10-10 出版日期:2022-12-08 发布日期:2022-12-23
  • 通讯作者: Wei Fang E-mail:wei_fang@fudan.edu.cn
  • 基金资助:
    Project supported by the National Basic Research Programs of China (Grant No. 2021YFA1400503), the National Natural Science Foundation of China (Grant No. 11934003), the Beijing Natural Science Foundation (Grant No. Z200004), and the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB33010400).

Concerted versus stepwise mechanisms of cyclic proton transfer: Experiments, simulations, and current challenges

Yi-Han Cheng(程奕涵)1, Yu-Cheng Zhu(朱禹丞)1, Xin-Zheng Li(李新征)1,2,3,4, and Wei Fang(方为)5,6,†   

  1. 1 State Key Laboratory for Artificial Microstructure and Mesoscopic Physics, Frontier Science Center for Nano-optoelectronics and School of Physics, Peking University, Beijing 100871, China;
    2 Interdisciplinary Institute of Light-Element Quantum Materials and Research Center for Light-Element Advanced Materials, Peking University, Beijing 100871, China;
    3 Peking University Yangtze Delta Institute of Optoelectronics, Nantong 226010, China;
    4 Collaborative Innovation Center of Quantum Matter, Peking University, Beijing 100871, China;
    5 Department of Chemistry, Fudan University, Shanghai 200438, China;
    6 State Key Laboratory of Molecular Reaction Dynamics and Center for Theoretical Computational Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
  • Received:2022-09-02 Revised:2022-10-08 Accepted:2022-10-10 Online:2022-12-08 Published:2022-12-23
  • Contact: Wei Fang E-mail:wei_fang@fudan.edu.cn
  • Supported by:
    Project supported by the National Basic Research Programs of China (Grant No. 2021YFA1400503), the National Natural Science Foundation of China (Grant No. 11934003), the Beijing Natural Science Foundation (Grant No. Z200004), and the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB33010400).

摘要: Proton transfer (PT) is a process of fundamental importance in hydrogen (H)-bonded systems. At cryogenic or moderate temperatures, pronounced quantum tunneling may happen due to the light mass of H. Single PT processes have been extensively studied. However, for PT involving multiple protons, our understanding remains in its infancy stage due to the complicated interplay between the high-dimensional nature of the process and the quantum nature of tunneling. Cyclic H-bonded systems are typical examples of this, where PT can happen separately via a "stepwise" mechanism or collectively via a "concerted" mechanism. In the first scenario, some protons hop first, typically resulting in metastable intermediate states (ISs) and the reaction pathway passes through multiple transition states. Whilst in the concerted mechanism, all protons move simultaneously, resulting in only one barrier along the path. Here, we review previous experimental and theoretical studies probing quantum tunneling in several representative systems for cyclic PT, with more focus on recent theoretical findings with path-integral based methods. For gas-phase porphyrin and porphycene, as well as porphycene on a metal surface, theoretical predictions are consistent with experimental observations, and enhance our understanding of the processes. Yet, discrepancies in the PT kinetic isotope effects between experiment and theory appear in two systems, most noticeably in water tetramer adsorbed on NaCl (001) surface, and also hinted in porphycene adsorbed on Ag (110) surface. In ice Ih, controversy surrounding concerted PT remains even between experiments. Despite of the recent progress in both theoretical methods and experimental techniques, multiple PT processes in cyclic H-bonded systems remain to be mysterious.

关键词: quantum tunneling, proton transfer, hydrogen bonding

Abstract: Proton transfer (PT) is a process of fundamental importance in hydrogen (H)-bonded systems. At cryogenic or moderate temperatures, pronounced quantum tunneling may happen due to the light mass of H. Single PT processes have been extensively studied. However, for PT involving multiple protons, our understanding remains in its infancy stage due to the complicated interplay between the high-dimensional nature of the process and the quantum nature of tunneling. Cyclic H-bonded systems are typical examples of this, where PT can happen separately via a "stepwise" mechanism or collectively via a "concerted" mechanism. In the first scenario, some protons hop first, typically resulting in metastable intermediate states (ISs) and the reaction pathway passes through multiple transition states. Whilst in the concerted mechanism, all protons move simultaneously, resulting in only one barrier along the path. Here, we review previous experimental and theoretical studies probing quantum tunneling in several representative systems for cyclic PT, with more focus on recent theoretical findings with path-integral based methods. For gas-phase porphyrin and porphycene, as well as porphycene on a metal surface, theoretical predictions are consistent with experimental observations, and enhance our understanding of the processes. Yet, discrepancies in the PT kinetic isotope effects between experiment and theory appear in two systems, most noticeably in water tetramer adsorbed on NaCl (001) surface, and also hinted in porphycene adsorbed on Ag (110) surface. In ice Ih, controversy surrounding concerted PT remains even between experiments. Despite of the recent progress in both theoretical methods and experimental techniques, multiple PT processes in cyclic H-bonded systems remain to be mysterious.

Key words: quantum tunneling, proton transfer, hydrogen bonding

中图分类号:  (Transition state theory and statistical theories of rate constants)

  • 82.20.Db
82.20.Wt (Computational modeling; simulation)