Symmetry and dynamics of FHF− anion in vacuum, in CD2Cl2 and in CCl4. Ab initio MD study of fluctuating solvent–solute hydrogen and halogen bonds,Physical Chemistry Chemical Physics

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Symmetry and dynamics of FHF− anion in vacuum, in CD2Cl2 and in CCl4. Ab initio MD study of fluctuating solvent–solute hydrogen and halogen bonds
Physical Chemistry Chemical Physics ( IF 2.9 ) Pub Date : 2017-09-12 00:00:00 , DOI: 10.1039/c7cp04493c
S. A. Pylaeva _{1,

2} , H. Elgabarty _{1,

2} , D. Sebastiani _{1,

2} , P. M. Tolstoy _{3,

4}

Affiliation

FHF⁻ anion is a classic example of a central-symmetric strongly hydrogen bonded system that has been intensively investigated both experimentally and theoretically. In this paper we focus on solvent effects on symmetry, structure and dynamics of the anion. The FHF⁻ anion is studied in vacuum, dissolved in CH₂Cl₂ and dissolved in CCl₄ by ab initio molecular dynamics simulations. We show that CH₂Cl₂ molecules form CH⋯F hydrogen bonds with lone pairs of fluorine atoms, while CCl₄ molecules form halogen bonds. These specific non-covalent solvent–solute interactions are cooperatively coupled to the FHF⁻ hydrogen bonds. The fluctuation of solvent molecules’ positions is the driving force changing the FHF⁻ hydrogen bond geometry. Most of the time, the anion is solvated asymmetrically, which leads to the asymmetric bridging particle position, though the time-averaged D_∞h symmetry is retained. Interestingly, this transient asymmetrization of FHF⁻ is more pronounced in CCl₄, than in CH₂Cl₂. We show that the ¹H and ¹⁹F NMR chemicals shifts react sensitively to the changes of anion's geometry and the limiting chemical shifts of free solvated FH and F⁻ are strongly solvent-dependent.

中文翻译：

对称性和动力学FHF的^-阴离子在真空，在CD ₂氯₂和四氯化碳₄。从头开始进行MD研究波动的溶剂-溶质氢和卤素键

FHF ^-阴离子是中央对称强烈氢键系统已被深入研究实验和理论上的一个典型的例子。在本文中，我们重点研究溶剂对阴离子的对称性，结构和动力学的影响。在FHF ^-阴离子研究了真空，将其溶于CH ₂氯₂并溶解于四氯化碳₄通过从头分子动力学模拟。我们表明，CH ₂ Cl ₂分子与孤对的氟原子形成CH⋯F氢键，而CCl ₄分子形成卤素键。这些特定的非共价溶剂-溶质相互作用与FHF协同偶联^-氢键。溶剂分子位置的变动改变FHF的驱动力^-氢键的几何形状。大部分时间，阴离子被不对称地溶剂化，这导致非对称桥接粒子的位置，尽管时间平均d _∞h对称性被保留。有趣的是，FHF的该瞬态asymmetrization^-更显着在四氯化碳₄，比CH₂氯₂。我们表明，¹ H和^19个F NMR化学品转移灵敏反应以阴离子的几何结构的变化和溶剂化FH和F的自由的限制化学位移^-强烈溶剂依赖性的。

更新日期：2017-09-20

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