Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6 Canada.
J Am Chem Soc. 2011 Jul 13;133(27):10559-67. doi: 10.1021/ja202096f. Epub 2011 Jun 13.
Studies of a series of urea-based anion receptors designed to probe the potential for anion recognition through combinations of hydrogen and halogen bonding are presented. Proton- and fluorine-NMR spectroscopy indicates that the two interactions act in concert to achieve binding of certain anions, a conclusion supported by computational studies. Replacement of the halogen-bond donating iodine substituent by fluorine (which does not participate in halogen bonding) enables estimation of the contribution of this interaction to the free energy of anion binding. Evidence for attractive contacts between anions and electron-deficient arenes arising from the use of perfluoroarene-functionalized ureas as control receptors is also discussed. The magnitude of the free energy contribution of halogen bonding depends both on the geometric features of the group linking the hydrogen- and halogen-bond donor groups and on the identity of the bound anion. The results are interpreted in relation to fundamental features of the halogen-bonding interaction, including its directionality and unusual preference for halides over oxoanions. Cooperation between two distinct noncovalent interactions leads to unusual effects on receptor selectivity, a result of fundamental differences in the interactions of halogen- and hydrogen-bond donor groups with anions.
研究了一系列基于尿素的阴离子受体，旨在通过氢键和卤素键的组合来探测阴离子识别的潜力。质子和氟 NMR 光谱表明，这两种相互作用协同作用，实现了某些阴离子的结合，这一结论得到了计算研究的支持。用氟（不参与卤素键合）取代卤素键供体碘取代基，使得能够估计这种相互作用对阴离子结合自由能的贡献。还讨论了使用全氟芳烃官能化的脲作为对照受体，阴离子与缺电子芳烃之间产生吸引力接触的证据。卤素键合的自由能贡献的大小既取决于连接氢键和卤素键供体基团的基团的几何特征，也取决于结合的阴离子的身份。结果根据卤素键合相互作用的基本特征进行了解释，包括其方向性和对卤化物而不是含氧阴离子的不寻常偏好。两种不同的非共价相互作用的合作导致受体选择性的异常影响，这是卤素键和氢键供体基团与阴离子相互作用的根本差异的结果。
