Luminescent metalloreceptors with pendant macrocyclic ionophore: Synthesis, characterization, electrochemistry and ion-binding study

Abstract Metalloreceptors containing ruthenium(II) bipyridine unit as fluorophore and pendant macrocyclic units as ionophore have been synthesized and their luminescence and electrochemical properties have been investigated. Ion-binding study of these fluoroionophore with the anions F − , Cl − , Br − , I − , H 2 PO 4 - , ClO 4 - , NO 3 - , BF 4 - , CH 3 COO − , and HSO 4 - and cations Na + , K + , Mg 2+ , Ca 2+ , Zn 2+ , Ba 2+ , Sr 2+ Cd 2+ , Hg 2+ , Pb 2+ and Cu 2+ , monitored by luminescence and 1 H NMR spectral changes, reveal strong interactions of H 2 PO 4 - and F − for 2 and 3 and of Cu 2+ only for 3 . Luminescence titrations for 2 and 3 have been carried out to determine binding constants ( K s ), and the calculated values are in the range 2.85 × 10 2 to 4.48 × 10 4 M −1 . The 1 H NMR spectral changes for 2 and 3 with the addition of increasing concentration of F − and H 2 PO 4 - exhibit substantial low-field shift of the CO NH proton indicating its involvement in complex formation with the anions. The H 2 PO 4 - adduct of 2 and 3 have been isolated and characterized by 1 H and 31 P NMR, mass and IR spectroscopy. The results are discussed in light of selectivity, structures of the anion bound complexes and their luminescence property.