Non-conventional bonding between organic molecules. The 'halogen bond' in crystalline systems
Non-conventional bonding between organic molecules. The 'halogen bond' in crystalline systems
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DOI：
10.1080/00268970802060674
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发表时间：
2008-01-01
影响因子：
1.7
通讯作者：
Gavezzotti, A.
中科院分区：
文献类型：
--
作者：
Gavezzotti, A.
当卤素原子与氧或氮原子紧密接触时，有机晶体中的分子间相互作用通过对剑桥结构数据库中现有晶体结构测定的调查和理论方法进行研究。短卤素-氧和-氮接触仅限于具有特殊电子和空间性质的系统。样品系统的能量井深度范围从几乎为零到约20 kJ mol(-1)，远小于氢键，而氢键几乎无法与氢键竞争。能量井的宽度表明一些短接触可能对应于许可（即能量中性）方法，甚至对应于压缩键合。最强的键只能通过芳香族碘来实现，芳香族碘被吸电子取代基高度活化，在具有强且空间无阻碍的路易斯碱的分子复合物中；只有在这种特殊情况下，卤素键才是晶体结构中最相关的内聚因子。在像素能量剖析方案中，对卤素键的最大贡献来自库仑加一阶偏振项。平行芳族体系之间的分散相互作用通常更稳定，在评估卤素化合物在极性晶体结构中形成线性聚集体的趋势时不应忽视。
The intermolecular interaction in organic crystals, when close contact between a halogen atom and an oxygen or nitrogen atom is present, is investigated by surveys of existing crystal structure determinations in the Cambridge Structural Database and by theoretical methods. Short halogen-oxygen and-nitrogen contacts are restricted to systems with peculiar electronic and steric properties. Energy well depths for sample systems range from almost nil to about 20 kJ mol(-1), considerably less than for hydrogen bonding, with which halogen bonding can hardly compete. The width of the energy wells suggests that some short contacts may correspond to just permissive (i.e. energetically neutral) approach, or even to compressed bonding. The strongest bond is attainable only by aromatic iodine, highly activated by electron-attracting substituents, in molecular complexes with strong and sterically unhindered Lewis bases; only in such special cases is the halogen bond the most relevant cohesive factor in the crystal structure. In the PIXEL energy dissection scheme, the largest contribution to halogen bonding comes from Coulombic plus first-order polarization terms. Dispersive interactions between parallel aromatic systems are often more stabilizing and should not be neglected in assessing the tendency of halogen compounds to form linear aggregates in polar crystal structures.