Metal Coordinated Urea Based Fluorescent Receptors for Anion Recognition

Two bis urea based acyclic receptors (1 and 2) containing two pyridyl moieties with different spacers are synthesized. These receptors are further transformed to metallo-macrocyclic receptors (3 and 4) by coordinating with metal center through pyridine ring ‘N’. The binding-behavior as well as selectivity of the receptors towards anions upon metal coordinated cyclization is studied and the results are compared with parent acyclic receptors. Receptors 2 and 4 containing a naphthalene moiety as a spacer as well as a fluorophore behave as ‘on-off’ sensors towards anions.