Issue 40, 2009

Synthesis, characterization, electrochemistry and ion-binding studies of ruthenium(II) bipyridine receptor molecules containing calix[4]arene-azacrown as ionophore

Abstract

A number of molecular receptors containing ruthenium(II) bipyridine moiety as fluorophore and calix[4]arene-azacrown hybrid molecule as ionophore have been synthesized and characterized. These receptors (1–4) exhibit strong 3MLCT luminescence bands in the range 613–618 nm. The cation-binding property of these fluoroionophores have been investigated with the ions Na+, K+, Mg2+, Ca2+, Cs+, Zn2+, Cd2+, Hg2+ and Pb2+ and the recognition event monitored by luminescence,1H NMR spectroscopy, the oxidation potential of metal ion and UV/Vis absorption studies. The luminescence study suggests complexation of all four receptors with Zn2+, Cd2+ and Hg2+ and for 2 and 3 also with Pb2+. The binding constants (Ks, except 4) and stoichiometries of the complexes have been calculated from the luminescence titration data, with values of Ks ranging from 2.53 × 105 to 6.27 × 103 M−1. The 1H NMR spectroscopy study exhibits interactions of Na+ and K+ with 1 and 4, K+ and Cs+ with 2, and K+ with 3. Binding constants with these metal ions have been calculated from 1H NMR titrations using computer programs or by a direct method depending on the type of change in the chemical shifts observed upon addition of metal ions. Stoichiometry of the complexes has been determined from Job's plot. Electrochemical properties of 1–4 have been studied in the absence and also in the presence of selected metal ions and the shift of the oxidation potentials of the Ru(II) in the presence of guest ions suggests an interaction of Na+, Hg2+ and Pb2+ with 1 and 2 but not with 3 and 4, indicating a selective electrochemical response towards certain metal ions. The results obtained are presented and discussed in light of ion-binding properties and methods of detection.

Graphical abstract: Synthesis, characterization, electrochemistry and ion-binding studies of ruthenium(II) bipyridine receptor molecules containing calix[4]arene-azacrown as ionophore

Supplementary files

Article information

Article type
Paper
Submitted
23 Mar 2009
Accepted
22 Jul 2009
First published
27 Aug 2009

Dalton Trans., 2009, 8683-8695

Synthesis, characterization, electrochemistry and ion-binding studies of ruthenium(II) bipyridine receptor molecules containing calix[4]arene-azacrown as ionophore

S. Patra and P. Paul, Dalton Trans., 2009, 8683 DOI: 10.1039/B905695E

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