Solvent Dependence of Double Proton Transfer in the Formic Acid?Formamidine Complex: Path Integral Molecular Dynamics Investigation
Solvent Dependence of Double Proton Transfer in the Formic Acid?Formamidine Complex: Path Integral Molecular Dynamics Investigation
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甲酸·甲脒络合物中双质子转移的溶剂依赖性：路径积分分子动力学研究
DOI：
10.1021/acs.jpca.7b07010
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
Tachikawa Masanori
中科院分区：
文献类型：
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作者：
Kungwan Nawee;Ngaojampa Chanisorn;Ogata Yudai;Kawatsu Tsutomu;Oba Yuki;Kawashima Yukio;Tachikawa Masanori
采用考虑核量子效应和热效应的ab初始积分分子动力学（AIPIMD）模拟方法研究了室温下甲酸-甲脒（FA-FN）配合物中双质子转移的溶剂依赖性。溶剂效应采用类导体筛选模型（COSMO）。与气相相比，低介电常数介质中质子转移势垒高度（<4.8）降低，FA-FN中两个重原子（O和N）之间出现双质子离域现象。对于介电常数为4.8的介质，由于溶剂的作用，发现这两个质子的机会更明显，它完全洗掉了质子转移屏障。在较高介电常数（>4.8）的介质中，离子种类比中性种类更稳定，甲酸阴离子和甲酸阳离子具有热力学稳定性。通过分子动力学模拟，发现在低介电常数（<4.8）介质中，由于不存在核量子效应，溶剂效应对质子转移势垒的降低不如AIPIMD明显。随着介质介电常数的增大，FA-FN配合物的运动也有显著差异。主成分分析详细揭示了这种差异。
Solvent dependence of double proton transfer in the formic acid–formamidine (FA–FN) complex at room temperature was investigated by means ofab initiopath integral molecular dynamics (AIPIMD) simulation with taking nuclear quantum and thermal effects into account. The conductor-like screening model (COSMO) was applied for solvent effect. In comparison with gas phase, double proton delocalization between two heavy atoms (O and N) in FA–FN were observed with reduced proton transfer barrier height in low dielectric constant medium (<4.8). For dielectric constant medium at 4.8, the chance of finding these two protons are more pronounced due to the solvent effect which completely washes out the proton transfer barrier. In the case of higher dielectric constant medium (>4.8), the ionic species becomes more stable than the neutral ones and the formate anion and formamidium cation are thermodynamically stable. Forab initiomolecular dynamics simulation, in low dielectric constant medium (<4.8) a reduction of proton transfer barrier with solvent effect is found to be less pronounced than the AIPIMD due to the absence of nuclear quantum effect. Moreover, the motions of FA–FN complex are significantly different with increasing dielectric constant medium. Such a difference is revealed in detail by the principal component analysis.