Department of Chemistry, University of New Orleans, LA 70148, USA.
Chemphyschem. 2013 Feb 4;14(2):278-94. doi: 10.1002/cphc.201200799. Epub 2013 Jan 9.
Halogen bonding is a noncovalent interaction that is receiving rapidly increasing attention because of its significance in biological systems and its importance in the design of new materials in a variety of areas, for example, electronics, nonlinear optical activity, and pharmaceuticals. The interactions can be understood in terms of electrostatics/polarization and dispersion; they involve a region of positive electrostatic potential on a covalently bonded halogen and a negative site, such as the lone pair of a Lewis base. The positive potential, labeled a σ hole, is on the extension of the covalent bond to the halogen, which accounts for the characteristic near-linearity of halogen bonding. In many instances, the lateral sides of the halogen have negative electrostatic potentials, allowing it to also interact favorably with positive sites. In this discussion, after looking at some of the experimental observations of halogen bonding, we address the origins of σ holes, the factors that govern the magnitudes of their electrostatic potentials, and the properties of the resulting complexes with negative sites. The relationship of halogen and hydrogen bonding is examined. We also point out that σ-hole interactions are not limited to halogens, but can also involve covalently bonded atoms of Groups IV-VI. Examples of applications in biological/medicinal chemistry and in crystal engineering are mentioned, taking note that halogen bonding can be "tuned" to fit various requirements, that is, strength of interaction, steric factors, and so forth.
卤键是一种非共价相互作用，由于其在生物系统中的重要性以及在电子、非线性光学活性和药物等多种领域设计新材料方面的重要性，受到了越来越多的关注。可以根据静电/极化和色散来理解这些相互作用；它们涉及共价键合卤素上的正静电势区域和负位点，例如路易斯碱的孤对。正电势，标记为σ孔，位于共价键向卤素的延伸部分，这解释了卤键的特征近线性。在许多情况下，卤素的横向侧面具有负静电势，允许其也与正位点有利地相互作用。在本次讨论中，在观察了一些卤键的实验观察结果之后，我们研究了σ孔的起源、控制其静电势大小的因素以及与负位点形成的复合物的性质。检查了卤键和氢键的关系。我们还指出，σ孔相互作用不仅限于卤素，还可以涉及 IV-VI 族共价键合的原子。在生物/药物化学和晶体工程中的应用示例被提及，并注意到卤键可以“调整”以适应各种要求，即相互作用强度、空间因素等。
