Solvent Dependence of Double Proton Transfer in the Formic Acid–Formamidine Complex: Path Integral Molecular Dynamics Investigation,The Journal of Physical Chemistry A

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Solvent Dependence of Double Proton Transfer in the Formic Acid–Formamidine Complex: Path Integral Molecular Dynamics Investigation
The Journal of Physical Chemistry A ( IF 2.7 ) Pub Date : 2017-09-22 00:00:00 , DOI: 10.1021/acs.jpca.7b07010
Nawee Kungwan _{1,

2} , Chanisorn Ngaojampa _{1,

2} , Yudai Ogata ₃ , Tsutomu Kawatsu _{3,

4} , Yuki Oba ₃ , Yukio Kawashima ₅ , Masanori Tachikawa ₃

Affiliation

Solvent dependence of double proton transfer in the formic acid–formamidine (FA–FN) complex at room temperature was investigated by means of ab initio path 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. For ab initio molecular 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.

中文翻译：

甲酸-甲am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

通过从头算研究了室温下甲酸-甲form（FA-FN）络合物中双质子转移的溶剂依赖性考虑核量子和热效应的路径积分分子动力学（AIPIMD）模拟。采用类似导体的屏蔽模型（COSMO）来实现溶剂效应。与气相相比，在低介电常数介质（<4.8）中，观察到FA-FN中两个重原子（O和N）之间的双质子离域，并降低了质子传递势垒高度。对于介电常数为4.8的介质，由于溶剂效应完全洗净了质子传递势垒，因此找到这两个质子的机会更加明显。在较高介电常数介质（> 4.8）的情况下，离子物质比中性物质更稳定，并且甲酸根阴离子和甲and阳离子在热力学上稳定。对于从头分子动力学模拟发现，由于缺乏核量子效应，在低介电常数介质（<4.8）中，具有溶剂效应的质子转移势垒的减少不如AIPIMD明显。此外，随着介电常数介质的增加，FA-FN配合物的运动也存在显着差异。通过主成分分析详细揭示了这种差异。

更新日期：2017-09-22

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