Pyridine‐Based Macrocyclic and Open Receptors for Urea

Abstract

Pyridine-based macrocyclic and open receptors 1-4 have been designed, synthesized and characterized. The macrocycle 1 was characterized by single crystal X-ray spectroscopy. Compound 2 selectively binds and recognizes urea in CHCl 3 . Fluorescence spectroscopy shows that compound 2 selectively displays quenching of monomer emission followed by formation of an intramolecular excimer upon hydrogen bond mediated complexation of urea. This distinguishes urea from thiourea. The fluorometric detection of urea has also been performed with the open receptors 3 and 4 in CHCl 3 . The detailed study reveals the effectivity of 2 in fluorescence sensing of urea over the structures 3 and 4. The urea recognition properties of receptors were evaluated by 1 H NMR, fluorescence and UV-vis studies.[a] Dr.