Toward Molecular Recognition: Three-Point Halogen Bonding in the Solid State and in Solution

A well-defined three-point interaction
based solely on halogen
bonding is presented. X-ray structural analyses of tridentate halogen
bond donors (halogen-based Lewis acids) with a carefully chosen triamine
illustrate the ideal geometric fit of the Lewis acidic axes of the
former with the Lewis basic centers of the latter. Titration experiments
reveal that the corresponding binding constant is about 3 orders of
magnitude higher than that with a comparable monodentate amine. Other,
less perfectly fitting multidentate amines also bind markedly weaker.
Multipoint interactions like the one presented herein are the basis
of molecular recognition, and we expect this principle to further
establish halogen bonding as a reliable tool for solution-phase applications.

本文报道了一种完全基于卤键（halogen bonding）的明确三点相互作用体系。针对精心筛选的三胺与三齿卤键供体（tridentate halogen bond donors，卤基路易斯酸（halogen-based Lewis acids））开展的X射线结构分析证实，前者的路易斯酸性轴与后者的路易斯碱性中心可实现理想的几何匹配。滴定实验结果显示，该体系的结合常数相较于同等单齿胺体系高出约3个数量级。其他几何匹配度欠佳的多齿胺，其结合能力也显著更弱。如本文所报道的这类多点相互作用是分子识别的核心基础，我们预期该原理将进一步确立卤键作为溶液相应用可靠工具的地位。