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Switching of Protonation Sites in Hydrated Nicotine via a Grotthuss Mechanism
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2024-01-23 , DOI: 10.1021/jacs.3c08922 Yuika Okura 1 , Garrett D Santis 2 , Keisuke Hirata 1, 3 , Vasilios S Melissas 4 , Shun-Ichi Ishiuchi 1, 3, 5 , Masaaki Fujii 3, 5, 6 , Sotiris S Xantheas 2, 3, 7
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2024-01-23 , DOI: 10.1021/jacs.3c08922 Yuika Okura 1 , Garrett D Santis 2 , Keisuke Hirata 1, 3 , Vasilios S Melissas 4 , Shun-Ichi Ishiuchi 1, 3, 5 , Masaaki Fujii 3, 5, 6 , Sotiris S Xantheas 2, 3, 7
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The switching of the protonation sites in hydrated nicotine, probed by experimental infrared (IR) spectroscopy and theoretical ab initio calculations, is facilitated via a Grotthuss instead of a bimolecular proton transfer (vehicle) mechanism at the experimental temperature (T = 130 K) as unambiguously confirmed by experiments with deuterated water. In contrast, the bimolecular vehicle mechanism is preferred at higher temperatures (T = 300 K) as determined by theory. The Grotthuss mechanism for the concerted proton transfer results in the production of nicotine’s bioactive and addictive pyrrolidine-protonated (Pyrro-H+) protomer with just 5 water molecules. Theoretical analysis suggests that the concerted proton transfer occurs via hydrogen-bonded bridges consisting of a 3 water molecule “core” that connects the pyridine protonated (Pyri-H+) with the pyrrolidine-protonated (Pyrro-H+) protomers. Additional water molecules attached as acceptors to the hydrogen-bonded “core” bridge result in lowering the reaction barrier of the concerted proton transfer down to less than 6 kcal/mol, which is consistent with the experimental observations.
中文翻译：
通过 Grotthuss 机制切换水合尼古丁中的质子化位点
通过实验红外 (IR) 光谱和理论从头计算探测，水合尼古丁中质子化位点的转换是通过在实验温度 ( T = 130 K) 下通过 Grotthuss 而不是双分子质子转移（载体）机制来促进的，如下所示氘化水实验明确证实了这一点。相反，根据理论确定，双分子载体机制在较高温度（ T = 300 K）下更受欢迎。 Grotthuss 协同质子转移机制导致产生尼古丁的生物活性和成瘾性吡咯烷质子化 (Pyrro-H + ) 原体，仅含 5 个水分子。理论分析表明，协同质子转移通过氢键桥发生，该氢键桥由 3 个水分子“核心”组成，连接吡啶质子化 (Pyri-H + ) 和吡咯烷质子化 (Pyrro-H + ) 原聚体。作为受体附着在氢键“核心”桥上的额外水分子导致协同质子转移的反应势垒降低至小于 6 kcal/mol，这与实验观察结果一致。
更新日期：2024-01-23
中文翻译：
通过 Grotthuss 机制切换水合尼古丁中的质子化位点
通过实验红外 (IR) 光谱和理论从头计算探测，水合尼古丁中质子化位点的转换是通过在实验温度 ( T = 130 K) 下通过 Grotthuss 而不是双分子质子转移（载体）机制来促进的，如下所示氘化水实验明确证实了这一点。相反，根据理论确定，双分子载体机制在较高温度（ T = 300 K）下更受欢迎。 Grotthuss 协同质子转移机制导致产生尼古丁的生物活性和成瘾性吡咯烷质子化 (Pyrro-H + ) 原体，仅含 5 个水分子。理论分析表明，协同质子转移通过氢键桥发生，该氢键桥由 3 个水分子“核心”组成，连接吡啶质子化 (Pyri-H + ) 和吡咯烷质子化 (Pyrro-H + ) 原聚体。作为受体附着在氢键“核心”桥上的额外水分子导致协同质子转移的反应势垒降低至小于 6 kcal/mol，这与实验观察结果一致。
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