Hirata Keisuke, Akasaka Kyota, Dopfer Otto, Ishiuchi Shun-Ichi, Fujii Masaaki
Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology 4259 Nagatsuta-cho, Midori-ku Yokohama 226-8503 Japan
Department of Chemistry, School of Science, Tokyo Institute of Technology 2-12-1 Ookayama, Meguro-ku Tokyo 152-8550 Japan.
Chem Sci. 2024 Jan 19;15(8):2725-2730. doi: 10.1039/d3sc05455a. eCollection 2024 Feb 22.
Proton transfer (PT) is one of the most ubiquitous reactions in chemistry and life science. The unique nature of PT has been rationalized not by the transport of a solvated proton (vehicle mechanism) but by the Grotthuss mechanism in which a proton is transported to the nearest proton acceptor along a hydrogen-bonded network. However, clear experimental evidence of the Grotthuss mechanism has not been reported yet. Herein we show by infrared spectroscopy that a vehicle-type PT occurs in the penta- and hexahydrated clusters of protonated -aminobenzoic acid, while Grotthuss-type PT is observed in heptahydrated clusters, indicating a change in the PT mechanism depending on the degree of hydration. These findings emphasize the importance of the usually ignored vehicle mechanism as well as the degree of hydration. It highlights the possibility of controlling the PT mechanism by the number of water molecules in chemical and biological environments.
质子转移（PT）是化学和生命科学中最普遍存在的反应之一。PT的独特性质并非通过溶剂化质子的传输（载体机制）来解释，而是通过Grotthuss机制来解释，即质子沿着氢键网络传输到最近的质子受体。然而，尚未有关于Grotthuss机制的确切实验证据报道。在此，我们通过红外光谱表明，在质子化对氨基苯甲酸的五水合物和六水合物簇中发生载体型PT，而在七水合物簇中观察到Grotthuss型PT，这表明PT机制随水合程度而变化。这些发现强调了通常被忽视的载体机制以及水合程度的重要性。它突出了在化学和生物环境中通过水分子数量控制PT机制的可能性。
