Allosteric effects in a tetrapodal imidazolium-derived calix[4]arene anion receptor

Abstract

A ditopic tetrapodal imidazolium-based 1,3-alternate calix[4]arene host binds anions as 1 : 2 complexes via a range of CH...anion hydrogen bonds. Allosteric enhancement of the affinity for the second chloride anion is observed. X-Ray crystal structures of the chloride, bromide and nitrate complexes suggest that this behaviour is linked to inter-binding site communication mediated by the calixarene framework. The imidazolium groups exist as either in-out or out-out conformers with respect to the calixarene, with the chloride complex exhibiting conformational isomorphism such that both forms are present in the same crystal structure.

Structural Diversity of Copper(I)–N‐Heterocyclic Carbene Complexes; Ligand Tuning Facilitates Isolation of the First Structurally Characterised Copper(I)–NHC Containing a Copper(I)–Alkene Interaction

“…The presence of anion-interactions in these structures may facilitate the use of imidazolium salts as anion-binders. [36,37] Reaction should be taken when interpreting the ESI+ mass spectra of copper(I)-NHC complexes, since their labile nature can lead to ligand scrambling resulting in the appearance of bis-NHC species in samples of pure mono-NHC compounds. This ligand scrambling behaviour is well documented for silver(I)-NHC complexes.…”

Recognition and sensing of anions through synergistic effects using simple benzimidazolium-urea receptors

“…The angle C8-H8A···Cl1 is 126.04°, suggesting the ionic − hydrogen bond is weaker than that observed other receptors [61,62]. Moreover, the crystal structure reveals that the chloride anion forms strong hydrogen bonds with two urea protons (H3B, and H4C), as well as forming a hydrogen bond with a proton of the aromatic benzene ring (H4A).…”

Chemical Biology: What is Its Role in Drug Discovery?

“…In the thiourea example, a bidirectional PET-based system was shown to be responsive to AcO -and H 2 PO 4 -anions as well as fluoride (Veale et al, 2009). The importance of allosteric effects has been assessed in a tetrapodal imidazolium-derived calix [4]arene receptor that recognises a range of anions (Willans et al, 2009). The use of porphyrin and N-confused porphyrin systems to detect anions has also been progressed (Toganoh et al, 2009).…”