A zinc–salophen/bile-acid conjugate receptor solubilized by CTABr micelles binds phosphate in water

Abstract

Receptor 1, composed of two deoxycholic acid moieties appended to a Zn–salophen complex, was prepared, characterized and tested for anion binding by ¹H NMR and UV-vis spectroscopic techniques. While in polar DMSO, 1 is able to bind phosphate (K = ∼700 M⁻¹), the addition of water severely diminishes the association. In a 1 : 9 water–DMSO mixture, the binding constant K is only ca. 20 M⁻¹. Notably, in an aqueous solution of CTABr micelles (CTABr 10 mM, cmc = ∼1 mM), the zinc–salophen conjugate 1, due to its two non-polar bile-acid moieties, becomes solubilized and, most importantly, it almost completely recovers its binding ability towards phosphate, displaying a remarkable affinity (K = ∼450 M⁻¹) in water.