Metal-promoted shift of equilibrium between the two fluorescent forms of a synthetic macrocycloureide in view of designing chemical sensors

Abstract

The emergence of the fiber-optic sensor era has stimulated investigations to create synthetic fluororeceptors capable of signaling the binding of metal ions. To fulfill this purpose, a new concept is presented: the metal-promoted shift of equilibrium between the two fluorescent forms of a synthetic receptor able to dimerize and to specifically recognize a metal ion by multiple non-covalent bonds. The thermodynamics of the dimerization itself and the dimer-zinc interactions are analyzed in terms of association constants. It is demonstrated that finely tuning the equilibrium between the monomeric and dimeric forms by controlling the pH, permits the alternate selective recognition and signaling of zinc or cadmium.