Anion Recognition by a Pincer-Type Host Constructed from Two Polyamide Macrocyclic Frameworks Jointed by a Photo-Addressable Azobenzene Switch

Abstract

A sterically crowded light-responsive host 1 was synthetized with a 93% yield by applying a post-functionalization protocol utilizing the double amidation of 4,4′-azodibenzoyl dichloride with a readily available 26-membered macrocyclic amine. X-ray structures of two hydrates of trans-1 demonstrate a very different alignment of the azobenzene linkage, which is involved in T-shape or parallel-displaced π⋯π stacking interactions with the pyridine-2,6-dicarboxamide moieties from the macrocyclic backbone. Despite the rigidity of the macrocyclic framework, which generates a large steric hindrance around the azobenzene chromophore, the host 1 retains the ability to undergo a reversible cis⟷trans isomerization upon irradiation with UVA (368 nm) and blue (410 nm) light. Moreover, thermal cis→trans back-isomerization (ΔG0 = 106.5 kJ∙mol−1, t½ = 141 h) is markedly slowed down as compared to the non-macrocyclic analog. 1H NMR titration experiments in DMSO-d6/0.5% water solution reveal that trans-1 exhibits a strong preference for dihydrogenphosphate (H2PO4−) over other anions (Cl−, MeCO2−, and PhCO2−), whereas the photogenerated metastable cis-1 shows lower affinity for the H2PO4− anion.

Synergistic regulation of chloride anion recognition using a triple‐functional sites receptor with two different cationic effectors

“…The recognition of anionic species play a critical role in many fundamental processes involving supramolecular chemistry, catalysis, environment, crystal and biology. [1][2][3][4][5][6] The basic principle of anion recognition is to design receptor molecule that can interact with anions via hydrogen bond, Lewis acid base interaction, Coulombic interaction, anion π interaction and halogen bond. In the past decades, a large number of functional groups and receptor molecules have been designed and used for anion recognitions, and thermodynamic methods have also been utilized to study the role of receptor conformations and solvent effects in the recognition process.…”

“…The recognition of anionic species play a critical role in many fundamental processes involving supramolecular chemistry, catalysis, environment, crystal and biology 1–6 . The basic principle of anion recognition is to design receptor molecule that can interact with anions via hydrogen bond, Lewis acid base interaction, Coulombic interaction, anion π interaction and halogen bond.…”