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

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−, H2PO4-, ClO4-, NO3-, BF4- , CH3COO−, and HSO4- and cations Na+, K+, Mg2+, Ca2+, Zn2+, Ba2+, Sr2+ Cd2+, Hg2+, Pb2+ and Cu2+, monitored by luminescence and 1H NMR spectral changes, reveal strong interactions of H2PO4- and F− for 2 and 3 and of Cu2+ only for 3. Luminescence titrations for 2 and 3 have been carried out to determine binding constants (Ks), and the calculated values are in the range 2.85 × 102 to 4.48 × 104 M−1. The 1H NMR spectral changes for 2 and 3 with the addition of increasing concentration of F− and H2PO4- exhibit substantial low-field shift of the CONH   proton indicating its involvement in complex formation with the anions. The H2PO4- adduct of 2 and 3 have been isolated and characterized by 1H and 31P NMR, mass and IR spectroscopy. The results are discussed in light of selectivity, structures of the anion bound complexes and their luminescence property.

Graphical abstractMetalloreceptors containing pendant macrocyclic units as ionophore have been synthesized and their ion-binding study with a large number of anions and cations, monitored by luminescence and 1H NMR, suggest strong complexation with F− and H2PO4- and also with Cu2+ in one case.Figure optionsDownload full-size imageDownload as PowerPoint slide