Heteroditopic thiacalix[4]arene receptor having ester and bipyridyl moieties for ions binding with positive/negative allosteric effect

A novel ditopic receptor possessing two complexation sites and bearing 1,3-alternate conformation based thiacalix[4]arene was prepared. The binding behaviors with Na⁺, K⁺ and Ag⁺ ions have been examined by ¹H NMR titration experiment in (CDCl₃/CD ₃CN; 10:1, v/v) solution. The job plots proves 1:1 complexation of 1,3-alternate-4 with Na⁺, K⁺ and Ag⁺ ions. Although the formation of heterogeneous dinuclear complexes was not clearly observed, the exclusive formation of mononuclear complexes of 1,3-alternate-4 with metal cations is of particular interest with positive/negative allosteric effect in thiacalix[4]arene family. These findings further demonstrate that preorganization, suitable conformational changes and affinity have a pronounced effect on the complexation process between the two different arms placed at the two edges of the thiacalix[4]arene cavity.