Robertson Craig C, Wright James S, Carrington Elliot J, Perutz Robin N, Hunter Christopher A, Brammer Lee
Department of Chemistry , University of Sheffield , Brook Hill , Sheffield , S3 7HF , UK . Email:
Department of Chemistry , University of York , Heslington , York , YO10 5DD , UK . Email:
Chem Sci. 2017 Aug 1;8(8):5392-5398. doi: 10.1039/c7sc01801k. Epub 2017 Jun 1.
Control of intermolecular interactions is integral to harnessing self-assembly in nature. Here we demonstrate that control of the competition between hydrogen bonds and halogen bonds, the two most highly studied directional intermolecular interactions, can be exerted by choice of solvent (polarity) to direct the self-assembly of co-crystals. Competitive co-crystal formation has been investigated for three pairs of hydrogen bond and halogen bond donors, which can compete for a common acceptor group. These competitions have been examined in seven different solvents. Product formation has been determined and phase purity has been examined by analysis of powder X-ray diffraction patterns. Formation of hydrogen-bonded co-crystals is favoured from less polar solvents and halogen-bonded co-crystals from more polar solvents. The solvent polarity at which the crystal formation switches from hydrogen-bond to halogen-bond dominance depends on the relative strengths of the interactions, but is not a function of the solution-phase interactions alone. The results clearly establish that an appreciation of solvent effects is critical to obtain control of the intermolecular interactions.
控制分子间相互作用是利用自然界中自组装现象的关键所在。在此，我们证明了通过选择溶剂（极性）来控制氢键和卤键这两种研究最为深入的定向分子间相互作用之间的竞争，可以引导共晶体的自组装。我们研究了三对氢键和卤键供体之间的竞争性共晶体形成，它们可以争夺一个共同的受体基团。这些竞争在七种不同的溶剂中进行了考察。通过粉末X射线衍射图谱分析确定了产物的形成并检测了相纯度。极性较小的溶剂有利于形成氢键共晶体，而极性较大的溶剂则有利于形成卤键共晶体。晶体形成从氢键主导转变为卤键主导时的溶剂极性取决于相互作用的相对强度，但不仅仅是溶液相相互作用的函数。结果清楚地表明，了解溶剂效应对于控制分子间相互作用至关重要。
