Thiacalix[4]arene Derivatives Bearing Imidazole Units: A Ditopic Hard/Soft Receptor for Na⁺ and K⁺/Ag⁺ with an Allosteric Effect and a Reusable Extractant for Dichromate Anions

Abstract

Two novel receptors 5,11,17,23‐tetra‐tert‐butyl‐25,27‐bis[(ethoxycarbonyl)methoxy]‐26,28‐bis‐[1‐methyl‐(imidazole)meth‐oxy]‐2,8,14,20‐tetra‐thiacalix[4]arene (L1) and 5,11,17,23‐tetra‐tert‐butyl‐25,27‐bis‐[(benzyl)methoxy]‐26,28‐bis‐[1‐methyl‐(imidazole)‐methoxy]‐2,8,14,20‐tetrathiacalix[4]arene (L2) possessing imidazole moieties based on thiacalix[4]arene in the 1,3‐alternate conformation have been synthesized and characterized. The crystal structures of L1 and L2 have been determined. The binding behaviour towards Li+, Na+, K+ and Ag+ ions has been examined by 1H NMR titration experiments in (CDCl3/CD3CN; 10:1, v/v) solution. The exclusive formation of mononuclear complexes of L1 with metal cations is of particular interest revealing a negative allosteric effect in the thiacalix[4]arene family. Liquid‐liquid extraction experiments indicate that synthesized L2 can be utilized as an efficient reusable extractant for dichromate anion by controlling the pH of the aqueous solution.

Switchable silver-ion complexation by triazolated calix[4]semitubes

“…3 In contrast, in the multitopic hosts targeted to pairs of same-charge ions (which are cations in most cases), Coulomb repulsion between charged species competes with allosteric strengthening of binding efficiency. This furnishes either multinuclear complexes 4 or molecular switches, in which a first-bound ion relocates between the 'tops' or even moves out of the host in response to the appearance of another ion in the system, 5 thus enabling applications of such supramolecular structures in the design of sensors and molecular machines.…”

Synthesis, crystal structure and remote allosteric binding properties of cone thiacalix[4]pseudocrown receptors bearing anthraquinone function and different arms

“…[11][12][13][14] Thiacalix [4]arenes are a kind of versatile scaffolds for highly organized receptors because of their specic affinity and allosteric features in molecular recognition. [15][16][17][18][19][20][21] In recent years, many optical receptors have been designed and synthesized based on the thiacalix [4]arene scaffold. Excellent examples include quinoline, rhodamine, naphthalene, pyrene, as well as coumarin-appended thiacalix [4]arene receptors.…”