Microscopic Models for Proton Transfer in Water and Strongly Hydrogen-Bonded Complexes with a Single-Well Proton Potential
Microscopic Models for Proton Transfer in Water and Strongly Hydrogen-Bonded Complexes with a Single-Well Proton Potential
复制标题
水和具有单井质子势的强氢键配合物中质子转移的微观模型
DOI：
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发表时间：
2004
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影响因子：
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通讯作者：
J. Ulstrup
中科院分区：
文献类型：
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作者：
A. Kuznetsov;J. Ulstrup
本文将最近提出的长氢键给体-受体复合物中质子转移的一种新机制和形式应用于液态水中的质子转移。水合氢离子的“结构扩散”被认为是完全绝热的过程，其中两个最接近的水分子的同步受阻平移进入和离开反应复合物是关键步骤。水分子在双阱势中诱导质子从供体到受体的“门控”移位，同时这些分子与质子供体和受体之间的氢键断裂/形成。还考虑了Zundel配合物中作为“结构扩散”的短程和长程质子转移。的理论形式主义示出了使用莫尔斯，指数，和谐波分子的潜力。这种方法被扩展到强氢键供体-受体复合物中的质子转移。然而，与上述模型[1]相反，供体和受体部分之间的短氢键完全侵蚀了沿质子转移模式的势垒沿着。这介绍了一些物理模式的差异，从质子转移反应在真正的双阱势与有限的质子转移势垒的过渡配置相对于环境的核坐标。这种差异特别适用于动力学同位素效应的起源。我们明确讨论了水溶液中过量质子电导率的细节，但概念和形式主义广泛适用于酸碱反应，质子传导通道，和其他强氢键O-和N-质子供体-受体系统。
A new mechanism and formalism for proton transfer in donor-acceptor complexes with long hydrogen bonds introduced recently [1], is applied to a proton transfer in liquid water. “Structural diffusion” of hydroxonium ions is regarded as totally adiabatic process, with synchronous hindered translation of two closest water molecules to and from the reaction complex as crucial steps. The water molecules induce a “gated” shift of the proton from the donor to the acceptor in the double-well potential with simultaneous breaking/formation of hydrogen bonds between these molecules and the proton donor and acceptor. The short-range and long-range proton transfer as “structural diffusion” of Zundel complexes is also considered. The theoretical formalism is illustrated with the use of Morse, exponential, and harmonic molecular potentials. This approach is extended to proton transfer in strongly hydrogen-bonded donor-acceptor complexes. In contrast to the above model [1], the short hydrogen bond between the donor and acceptor moieties, however, completely erodes the barrier along the proton transfer mode. This introduces some physical pattern differences from proton transfer reactions in truly double-well potentials with a finite proton transfer barrier at the transition configuration with respect to the environmental nuclear coordinates. The differences apply particularly to the origin of the kinetic isotope effect. We discuss explicitly details of the excess proton conductivity in aqueous solution, but the concepts and formalism apply broadly to acid-base reactions, proton conduction channels, and other strongly hydrogen-bonded O- and N-proton donor-acceptor systems.