Lawrence Berkeley National Laboratory

Thiacalix[4]arene receptors with two thiourea moieties and two 2-pyridyl moieties exhibited a heteroditopic dinuclear receptor with F − and Ag + ions by a positive allosteric effect. The synthesis of three new heteroditopic receptors (5a–c) which are based on thiacalix[4]arenes in the 1,3-alternate conformation is reported herein. These new receptors each have two thiourea moieties linking phenyl groups, two of which are substituted with electron-withdrawing groups at their para -positions, and at the opposite side of the thiacalix[4]arene cavity, with two 2-pyridylmethyl groups. One example (5a) was also characterized by X-ray crystallography. A limited 1 H-NMR and UV-vis anion complexation study was conducted. DFT computational determinations indicated that 5c, which has strongly electron-withdrawing NO 2 groups, had the most effective recognition ability towards the selected anions. The binding of Ag + at the 2-pyridyl moieties, and the binding of the anions at the two thiourea NH groups of the p -substituted phenylthioureido moieties, respectively, was also investigated. The appearance of a positive allosteric effect with receptor 5b was also found using 1 H-NMR titration experiments.