Chalcogen Bond Mediated Enhancement of Cooperative Ion‐Pair Recognition

Abstract

A series of heteroditopic receptors containing halogen bond (XB) and unprecedented chalcogen bond (ChB) donors integrated into a 3,5‐bis‐triazole pyridine structure covalently linked to benzo‐15‐crown‐5 ether motifs exhibit remarkable cooperative recognition of halide anions. Multi‐nuclear 1 H, 13 C, 125 Te and 19 F NMR, ion pair binding investigations reveal sodium cation–benzo‐crown ether binding dramatically enhances the recognition of bromide and iodide halide anions, with the chalcogen bonding heteroditopic receptor notably displaying the largest enhancement of halide binding strength of over two hundred‐fold, in comparison to the halogen bonding and hydrogen bonding heteroditopic receptor analogues. DFT calculations suggest crown ether sodium cation complexation induces a polarisation of the sigma hole of ChB and XB heteroditopic receptor donors as a significant contribution to the origin of the unique cooperativity exhibited by these systems.

From Heteroditopic to Multitopic Receptors for Ion‐Pair Recognition: Advances in Receptor Design and Applications

“…A very recent report this year, 2020, by Beer et al describes a direct comparison of unprecedented ChB ion-pair recognition with XB and HB using a series of structurally homologous heteroditopic receptors 5 a-c incorporating XB, chalcogen bonding (ChB) and HB donor groups covalently linked with benzo-15-crown-5 ether motifs ( Figure 4). [16] Extensive 1 H NMR titration experiments in 10 % d 6 -DMSO/CDCl 3 solution with TBABr and TBAI, in the presence and absence of sodium cations determined K a (Na + )/K a (None) cooperativity factors (α) for each receptor, summarised in Table 1. All receptors demonstrated positive cooperativity (α > 1), consistent with favourable electrostatic interactions.…”

Chalcogen Bonding Ion‐Pair Cryptand Host Discrimination of Potassium Halide Salts

“…[18][19][20][21] Despite this, their incorporation into heteroditopic structural host frameworks is rare, with only a handful of examples of XB and one ChB ion-pair receptor reported to date. [13,[22][23][24][25] Herein, we report the first sigma-hole heteroditopic cryptands, which feature a dibenzo-30-crown-10 (DB30C10) motif for potassium cation binding, bridged by bidentate ChB, and XB donors for anion recognition. (Figure 1).…”

“…The sigma‐hole non‐covalent interactions, halogen bonding (XB) and chalcogen bonding (ChB), have been shown to exhibit potent anion binding strength and selectivities, which includes superior enantioselectivity [17] and sensory response output, in comparison to analogous hydrogen bonding (HB) receptor analogues [18–21] . Despite this, their incorporation into heteroditopic structural host frameworks is rare, with only a handful of examples of XB and one ChB ion‐pair receptor reported to date [13,22–25] …”

Halogen Bonding Tetraphenylethene Anion Receptors: Anion‐Induced Emissive Aggregates and Photoswitchable Recognition

“…Within the rapidly expanding field of supramolecular anion host‐guest chemistry, halogen bonding and chalcogen bonding intermolecular interactions have emerged as a valuable addition to the supramolecular toolbox [24–27] . These sigma hole interactions frequently confer enhanced anion affinity and unique selectivity profiles relative to hydrogen bonding (HB) interactions within anion receptors, [28–37] sensors [38–40] and transmembrane anion transporters [41–44] …”