Bernal Ivan, Watkins Steven F
Chemistry Department, Hunter College, City University of New York, New York, NY 10021, USA.
Acta Crystallogr C. 2013 Aug;69(Pt 8):808-10. doi: 10.1107/S0108270113015114. Epub 2013 Jul 9.
Intermolecular hydrogen bonding is an integral part of many crystal structures. Hydrogen bonding sometimes results in one-, two- or three-dimensional supramolecular assemblies, a common feature of which is positional disorder of H atoms related to space-group symmetry. Yet some reported structures fail to include all possible donor–acceptor close contacts, or to seek H-atom electron densities associated with apparent D-H∙∙∙A trios, while some H-atom positions violate principles of chemistry or crystal physics. Modern diffraction equipment and sophisticated computing systems provide high-quality data; thus, failure to characterize and report fully an accurate, complete and physically correct hydrogen-bonding model should not be acceptable. We illustrate the relevant issues with three published examples in the hope of slowing the proliferation of these problems, with the scientifically desirable goal of improving the accuracy of crystallographic models while also providing improved search keys for information retrieval.
分子间氢键是许多晶体结构不可或缺的一部分。氢键有时会导致一维、二维或三维超分子聚集体，其一个常见特征是与空间群对称性相关的H原子位置无序。然而，一些已报道的结构未能包含所有可能的供体-受体紧密接触，或者未能寻找与明显的D-H∙∙∙A三元组相关的H原子电子密度，而一些H原子位置违反了化学或晶体物理学原理。现代衍射设备和先进的计算系统可提供高质量数据；因此，未能充分表征和报告准确、完整且物理上正确的氢键模型是不可接受的。我们用三个已发表的例子来说明相关问题，希望减缓这些问题的扩散，实现提高晶体学模型准确性这一科学上理想的目标，同时也为信息检索提供更好的搜索关键词。
