Structure and dynamics of proton transfer in liquid imidazole. A molecular dynamics simulation.

Ailin Li, Zhen Cao, Yao Li, Tianying Yan, Panwen Shen

Institute of New Energy Material Chemistry, Tianjin Key Laboratory of Metal- and Molecule-Based Material Chemistry, Nankai University, Tianjin 300071, China.

The journal of physical chemistry. B 2012 Oct 25

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Proton transfer (PT) via the Grotthuss mechanism in liquid imidazole (im) at 393 K is studied with molecular dynamics simulation using a reactive multistate empirical valence bond (MS-EVB) model. It is found that the proton is tightly binded to an imidazole to form an imidazolium (imH(+)), which is solvated in a distorted Eigen-like complex (im-imH(+)-im), whereas the Zundel-like complex (im-H(+)-im) is rare. PT occurs via an Eigen-Zundel-Eigen scenario for switching the identity of imH(+) from an Eigen-like complex to another, intermediated by a Zundel-like complex. Structural and dynamical analyses demonstrate that PT in imidazole can be considered as a local event with very short spatial/temporal correlation, characterized by a few "rattling" or recurrent PT events. At long time scale, the trend of the PT correlation function may be recast with the diffusion model of reversible geminate recombination toward the power-law decay. The formation of the hydrogen bonds (HBs) for the imidazole molecules between the first and second solvation shell of imH(+) is crucial to pave the PT pathway. The above features may be understood by the flexibility of the HBs in liquid imidazole, as a stable HB network is essential for the Grotthuss mechanism.

Citation

Ailin Li, Zhen Cao, Yao Li, Tianying Yan, Panwen Shen. Structure and dynamics of proton transfer in liquid imidazole. A molecular dynamics simulation. The journal of physical chemistry. B. 2012 Oct 25;116(42):12793-800