Imidazolium‐Based [1₄]Heterophanes as Models for Anion Recognition

Abstract

The significance of the reported dicationic [14]imidazoliophanes 4·2X relies on their ability to bind anions in polar media. Thus, imidazolium units represent the main structural motifs in the formation of unconventional (C–H)+···Cl– charge‐assisted hydrogen bonds which become the noncovalent forces driving the anionic interactions exhibited by dications 4·2X. Herein, we report the “3+1” convergent synthesis of the title macrocycles 4a–d·2X; their counteranion exchange using a strongly basic anion‐exchange resin (OH– form) and their structures have been examined by NMR spectroscopy. Solution studies in CD3CN and [D6]DMSO by 1H NMR spectroscopy have revealed the importance of the hydrogen bonds in controlling anion recognition.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

A Bidentate Halogen‐Bonding Bromoimidazoliophane Receptor for Bromide Ion Recognition in Aqueous Media

“…In contrast to the bromoimidazoliophanes, as expected [14] only one conformer species was detected and isolated.…”

“…[13] Inspired by the polyimidazolium receptor systems reported to date [14] and with the aim of contributing to the meagre quantitative data reported on halogen bonding receptor-anion association in solution, we describe herein the synthesis of a novel bidentate halogenbonding bromoimidazoliophane receptor which, by cooperative action of two preorganized halogen-bonding bromine donor atoms, is capable of selectively binding bromide ions strongly in competitive aqueous solvent media. Importantly, by comparison the protic imidazoliophane receptor analogue is a nonselective weak binder of halide ions.…”

Synthesis, structures and luminescence of three coordination polymers constructed from rigid 1,3,5-benzenetricarboxylic acid and flexible bis(imidazol-1-ylmethyl)-benzene

“…The flexible m-and p-bis(imidazol-1-ylmethyl)-benzene ligand were prepared by reacting 1,4-bis(bromomethyl)benzene/1,3-bis(bromomethyl)benzene with imidazole in dry CH 3 CN following a similar procedure using K 2 CO 3 as a base instead of KOH [16]. Other chemicals were of reagent grade and used as received without further purification.…”

Azolium-Linked Cyclophanes: Effects of Structure, Solvent, and Counteranions on Solution Conformation Behavior

“…At room temperature solutions of 11.2Br in DMSO-d 6 and methanol ( Figures S28 and S29) exhibited numerous broad signals over the entire 1 H NMR spectrum. The signals were consistent with multiple conformers undergoing exchange processes.…”

“…[2][3][4][5][6] Design of specific imidazolium cyclophane structures has led to cyclophanes that display improved binding to specific anions, e.g. In this paper we discuss the conformational behavior of cyclophanes bearing extended alkyl chains.…”