Engagement of CF3 Group in N-H•••F-C Hydrogen Bond in the Solution State: NMR Spectroscopy and MD Simulation Studies
Engagement of CF3 Group in N-H•••F-C Hydrogen Bond in the Solution State: NMR Spectroscopy and MD Simulation Studies
复制标题
DOI：
10.1021/jp310798d
复制
发表时间：
2013-01-31
影响因子：
3.3
通讯作者：
Suryaprakash, N.
中科院分区：
文献类型：
--
作者：
Chaudhari, Sachin Rama;Mogurampelly, Santosh;Suryaprakash, N.
报道了低极性溶剂中 CF3 基团与 N-H 中心点 F-C 氢键接合的明确证据，这是此类现象的首次观察。一维和二维 H-1、F-19 和天然丰富的 N-15 NMR 光谱研究令人信服地证实了溶液状态下存在这种弱分子相互作用。强有力而直接的证据来自对空间耦合的观察，例如(1h)J(FH)、(1h)J(FN)和(2h)J(FF)，其中自旋极化通过氢键传递。在一个有趣的例子中，含有两个 CF3 基团的分子同时参与氢键，其中氢键介导的偶联未反映在 NMR 谱中，F-19-F-19 NOESY 实验得出了确凿的证据。 (1)J(NH)、可变温度和溶剂引起的扰动的强度的显着偏差产生了额外的支持。 NMR 结果通过 DFT 计算和 MD 模拟得到证实，其中获得了氟参与两个和三个中心氢键的不同方式、它们的出现百分比和几何形状的定量信息。还计算了氢键相互作用能。
Unambiguous evidence for the engagement of CF3 group in N-H center dot center dot center dot F-C hydrogen bond in a low polarity solvent, the first observation of its kind, is reported. The presence of such weak molecular interactions in the solution state is convincingly established by one and two-dimensional H-1, F-19, and natural abundant N-15 NMR spectroscopic studies. The strong and direct evidence is derived by the observation of through-space couplings, such as, (1h)J(FH), (1h)J(FN), and (2h)J(FF), where the spin polarization is transmitted through hydrogen bond. In an interesting example of a molecule containing two CF3 groups getting simultaneously involved in hydrogen bond, where hydrogen bond mediated couplings are not reflected in the NMR spectrum, F-19-F-19 NOESY experiment yielded confirmatory evidence. Significant deviations in the strengths of (1)J(NH), variable temperature, and the solvent induced perturbations yielded additional support. The NMR results are corroborated by both DFT calculations and MD simulations, where the quantitative information on different ways of involvement of fluorine in two and three centered hydrogen bonds, their percentage of occurrences, and geometries have been obtained. The hydrogen bond interaction energies have also been calculated.