Monometallic rhenium(I) complexes as sensor for anions

Three new tricarbonyl rhenium(I) polypyridine complexes containing amide, urea and thiourea derivatives of 2,2′-bipyridine ligands L1–L3 have been synthesized, characterized and found to show significant UV–visible absorption spectral changes on the addition of anions CN−, F−, CH3COO− and H2PO4−. These spectral changes and 1H NMR titrations of complexes 1–3 with anions indicate strong binding of anions with the Re(I) complexes and the binding constants are in the range of 103–105 M− 1. The strong binding is attributed to the H-bond formation/deprotonation of single bondNH proton in the ligand and the selectivity of anion is in the order CN− > F− > CH3COO− > H2PO4−.