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Hydrogen atoms in bridging positions from quantum crystallographic refinements: influence of hydrogen atom displacement parameters on geometry and electron density
CrystEngComm ( IF 3.1 ) Pub Date : 2020-06-15 , DOI: 10.1039/d0ce00378f
Lorraine A. Malaspina 1, 2, 3, 4 , Anna A. Hoser 5, 6, 7, 8, 9 , Alison J. Edwards 10, 11, 12, 13 , Magdalena Woińska 5, 6, 7, 8, 9 , Michael J. Turner 13, 14, 15, 16, 17 , Jason R. Price 11, 13, 18, 19 , Kunihisa Sugimoto 20, 21, 22, 23, 24 , Eiji Nishibori 22, 25, 26, 27, 28 , Hans-Beat Bürgi 29, 30, 31, 32, 33 , Dylan Jayatilaka 13, 14, 15, 16, 17 , Simon Grabowsky 1, 2, 3, 4, 29
Affiliation  

Resonance-assisted hydrogen bonds (RAHBs) are exploited in chemical synthesis or serve as models for biologically relevant proton-transfer reactions [K. T. Mahmudov and A. J. L. Pombeiro, Chem. – Eur. J., 2016, 22, 16356–16398]. Their properties depend on the position of the hydrogen atom between donor and acceptor atoms. In the intramolecular RAHB of hydrogen maleate salts, this position is strongly influenced by the counter cation and varies from highly asymmetric to perfectly symmetric. This compound class is therefore ideally suited to investigate the factors determining geometry and electron density of intramolecular RAHBs. Here, it is shown that Hirshfeld atom refinements (HARs) of X-ray diffraction data of different hydrogen maleate salts can accurately and precisely match the hydrogen atom positions obtained from neutron diffraction and are independent of the model used for the hydrogen atom displacement parameters. Thus, the simplest, i.e. isotropic, HAR model can be used to locate hydrogen atoms also in bridging positions. In contrast, the determination of electron-density parameters with X-ray constrained wavefunction (XCW) fitting requires anisotropic, highly accurate hydrogen atom displacement parameters.

中文翻译:

量子晶体学精炼中桥接位置的氢原子:氢原子位移参数对几何形状和电子密度的影响

共振辅助氢键(RAHBs)可用于化学合成或用作生物学上相关的质子转移反应的模型[KT Mahmudov和AJL Pombeiro,Chem。- 欧元。J.,2016,22,16356–16398]。它们的性质取决于供体原子和受体原子之间氢原子的位置。在马来酸氢盐的分子内RAHB中,该位置受抗衡阳离子的影响很大,从高度不对称到完全对称。因此,该化合物类别非常适合研究决定分子内RAHBs的几何形状和电子密度的因素。在此表明,不同马来酸氢盐的X射线衍射数据的Hirshfeld原子细化(HARs)可以精确且精确地匹配从中子衍射获得的氢原子位置,并且与用于氢原子置换参数的模型无关。因此,最简单的,各向同性的HAR模型也可用于在桥连位置定位氢原子。相反,用X射线约束波函数(XCW)拟合确定电子密度参数需要各向异性,高精度的氢原子位移参数。
更新日期:2020-07-20
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