Anion recognition between the triurea receptor and phosphate anion is demonstrated as the cross‐linkage to build supramolecular polymer gels for the first time. A novel multi‐block copolymer ( 3) is designed to have functional triurea groups as cross‐linking units along the polymer main chain. By virtue of anion coordination between the triurea receptor and phosphate anion with a binding mode of 2:1, supramolecular polymer gels are then prepared based on anion recognition using 3 as the building block.
Exploring new noncovalent bonding motifs with reversibly tunable binding affinity is of fundamental importance in manipulating the properties and functions of supramolecular self-assembly systems and materials. Herein, for the first time, we demonstrate a unique visible-light-switchable telluro-triazole/triazolium-based chalcogen bonding (ChB) system in which the Te moieties are connected by azobenzene cores. The binding strengths between these azo-derived ChB receptors and the halide anions (Cl−, Br−) could be reversibly regulated upon irradiation by visible light of different wavelengths. The cis-bidentate ChB receptors exhibit enhanced halide anion binding ability compared to the trans-monodentate receptors. In particular, the telluro-triazolium-based ChB receptor can achieve both high and significantly photoswitchable binding affinities for halide anions, which enable it to serve as an efficient photocontrolled organocatalyst for ChB-assisted halide abstraction in a Friedel–Crafts alkylation benchmark reaction. 相似文献
The synthesis of a series of polyguanidinium salts of potential interest as anion complexones is described. Among the various synthetic methods investigated, the polyguanidinium salts were found to be most conveniently prepared from polyamines via polynitroguanidine intermediates. The complexation of phosphate and carboxylate anions by these complexones and by related polyammonium salts were studied by analysis of pH-metric titration data. The ligands studied from relatively stable complexes (log Ks = 2.0–4.0 for PO in water) which also present good selectivities in some cases. Both the stability and the selectivity of complexation are primarily governed by electrostatic forces and thus depend on charge accumulation in the interacting species; structural effects are also observed. Since the binding is primarily electrostatic, polyammonium salts from more stable complexes (at a given charge) than do polyguanidinium salts. However, whereas the complexation properties of the latter are independent of pH, the complexes of the former are observed only in the limited ranges of pH where both the protonated polyamine and the anion of interest can coexist. The polycationic ligands may, in principle, form chelate type anion complexes. Comparison with the corresponding single binding sites reveals an increase in complexation constant of about two or three orders of magnitude; this may be considered as a thermodynamic indication of a chelate effect for the polydentate ligands (by analogy with the well known effects displayed by cation complexones); however, structural data on the formation of chelate ‘rings’ are not yet available. The nature of the complexes and the prospects of anion complexones in various fields are discussed. 相似文献
First evidence for the existence of free trifluoromethyl anion CF3− has been obtained. The 3D‐caged potassium cation in [K(crypt‐222)]+ is inaccessible to CF3−, thus rendering it uncoordinated (“naked”). Ionic [K(crypt‐222)]+ CF3− has been characterized by single‐crystal X‐ray diffraction, solution NMR spectroscopy, DFT calculations, and reactivity toward electrophiles. 相似文献
First evidence for the existence of free trifluoromethyl anion CF3? has been obtained. The 3D‐caged potassium cation in [K(crypt‐222)]+ is inaccessible to CF3?, thus rendering it uncoordinated (“naked”). Ionic [K(crypt‐222)]+ CF3? has been characterized by single‐crystal X‐ray diffraction, solution NMR spectroscopy, DFT calculations, and reactivity toward electrophiles. 相似文献
