Halogen Bonding in Solution: Anion Recognition, Templated Self‐Assembly, and Organocatalysis

Abstract

The halogen bond is a supramolecular interaction between a Lewis-acidic region of a covalently bound halogen and a Lewis base. It has been studied widely in silico and experimentally in the solid state; however, solution-phase applications have attracted enormous interest in the last few years. This Minireview highlights selected recent developments in halogen bond interactions in solution, with a focus on the use of receptors based on halogen bonds in anion recognition and sensing, anion-templated self-assembly, as well as in organocatalysis.

Is There a Single Ideal Parameter for Halogen‐Bonding‐Based Lewis Acidity?

“…Still, there have been only a few studies in this area of research had been carried out before the mid‐1990s for the solid phase and before the mid‐2000s for complexes in solution . By now, however, halogen bonding is firmly established in crystal engineering and has found various applications in solution, including in anion binding, molecular recognition as well as organocatalysis…”

Iodide Discrimination by Tetra‐Iodotriazole Halogen Bonding Interlocked Hosts

“…[21][22][23][24][25][26][27][28] Combined with the highly directional halogen bond, MIMs have been shown to act as potent host structures for solution phase anion recognition in competitive aqueous-organic media, often exhibiting stronger anion association than their hydrogen bonding( HB) counterparts. [29][30][31] In particular,w eh ave recently employed the 3,5-bis(iodotriazole)-pyridinium motif in the construction of aX B [ 2]catenane capable of binding bromide andi odide anionss trongly (K a > 10 4 m À1 )v ia two convergent halogen bonds in the competitive solvent mixture 45:45:10 CDCl 3 /CD 3 OD/D 2 O. [32] In an effort to discriminateb etween the heavy halides, herein we designed an ovel potential four XB donort etra(iodotriazole)-pyridinium group to incorporate into macrocycle and axle components of MIM host struc-tural frameworks ( Figure 1).…”

Four‐Center Nodes: Supramolecular Synthons Based on Cyclic Halogen Bonding

“…Halogen bonding (commonly abbreviated as XB) is an interdisciplinary area of growing interest, as collaterally reflected in a substantial amount of reviews and text‐book considerations on the subject. The recently published review articles were devoted to basic aspects of XB and its role in crystal engineering and supramolecular chemistry, XB‐involving catalysis including noncovalent organic catalysis, synthetic coordination chemistry, polymer chemistry, noncovalent aspects of drug discovery, and, eventually, to the role of XB in human function . The phenomenon of XB is associated with the anisotropy of electron distribution in the halides that particularly sensitive to action of neighboring acceptor groups.…”