Bond orders for intermolecular interactions in crystals: charge transfer, ionicity and the effect on intramolecular bonds.
Bond orders for intermolecular interactions in crystals: charge transfer, ionicity and the effect on intramolecular bonds.
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晶体中分子间相互作用的键序：电荷转移、离子性和对分子内键的影响。
DOI：
10.1107/s2052252518010758
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发表时间：
2018-09-01
期刊：
影响因子：
3.9
通讯作者：
Thomas SP
中科院分区：
文献类型：
--
作者：
Alhameedi K;Karton A;Jayatilaka D;Thomas SP
探讨了分子晶体中氢键、卤键和硫代键等分子间相互作用的Roby-Gould键级数。键序数值将这些相互作用放在代表其相对强度的标度上，并结合化学家对键的概念。晶体中的分子间相互作用是起源于局域原子⋯原子相互作用，还是整体分子⋯分子紧密堆积的结果，这是一个持续争论的问题。在此背景下，新引入的罗比-古尔德键指数被报道为分子间的σ-空穴相互作用，如卤素键和硫族键，并与氢键的指数进行了比较。分析了从剑桥结构数据库(CSD)获得的一系列97个显示这些相互作用模体的晶体系统。与传统的键级估计相比，新方法分别估计了原子⋯原子和分子⋯分子的离子和共价键指数，从而揭示了这些相互作用的本质。在这些分子间相互作用区，通过电子布居的Hirshfeld原子分配，发现了从卤素/硫族键受体到键供体基团的电荷转移的一致趋势。这些结果，以及在相互作用区测试的“键序守恒”，证实了局域原子⋯原子相互作用在这些分子间结合基序的形成中的重要作用。
Roby–Gould bond orders for intermolecular interactions such as hydrogen bonds, halogen bonds and chalcogen bonds in molecular crystals have been explored. Bond-order values place these interactions on a scale representing their relative strengths, in conjunction with a chemist’s notion of bonds. The question of whether intermolecular interactions in crystals originate from localized atom⋯atom interactions or as a result of holistic molecule⋯molecule close packing is a matter of continuing debate. In this context, the newly introduced Roby–Gould bond indices are reported for intermolecular ‘σ-hole’ interactions, such as halogen bonding and chalcogen bonding, and compared with those for hydrogen bonds. A series of 97 crystal systems exhibiting these interaction motifs obtained from the Cambridge Structural Database (CSD) has been analysed. In contrast with conventional bond-order estimations, the new method separately estimates the ionic and covalent bond indices for atom⋯atom and molecule⋯molecule bond orders, which shed light on the nature of these interactions. A consistent trend in charge transfer from halogen/chalcogen bond-acceptor to bond-donor groups has been found in these intermolecular interaction regions via Hirshfeld atomic partitioning of the electron populations. These results, along with the ‘conservation of bond orders’ tested in the interaction regions, establish the significant role of localized atom⋯atom interactions in the formation of these intermolecular binding motifs.