Allosteric-Controlled Metal Specificity of a Ditopic Ligand

To twist or not to twist? A ditopic ligand, L1, that contains a potentially tetradentate pyridyl–thiazole ligand chain and a “external” crown ether unit is presented. Reaction of L1 with Cu+ or Zn2+ ions results in the formation of a dinuclear double helicate [Cu2(L1)2]2+ or a mononuclear [ZnL1]2+ species. This ditopic system changes its preference for Cu+ or Zn2+ ions on the inclusion of s‐block‐metal ions at the crown ether binding site (e.g., Sr2+ ions as shown in the scheme).