Abstract
AbstractA number of molecular receptors containing a ruthenium(II)/rhenium(I) bipyridine moiety as fluorophore and a crown ether, connected to the 4,4′‐positions of the bipyridine/phenanthroline unit through >C=O and ‐HC=N‐ spacers, as ionophore have been synthesised and characterised. The luminescence and electrochemical properties of these receptors have been studied. The cation‐binding properties of these molecules have been investigated with the cations Na+, K+, Rb+, Mg2+, Ca2+, Zn2+, Cd2+, Hg2+, Pb2+ and Cu2+ and the recognition event monitored by 1H NMR spectroscopy, luminescence, the oxidation potential of the metal ion and UV/Vis absorption studies. The emission intensities of complexes 1–3 are strongly quenched by the addition of Pb2+, Cu2+, Hg2+ and Na+, whereas a significant enhancement of the emission intensities is observed for 4 in the presence of Cu2+ and Hg2+ and for 5 in the presence of Cd2+ and Hg2+. Luminescence titrations for 1–5 with the above‐mentioned metal ions have been carried out. The binding constants (Ks) and stoichiometry of the complexes have been calculated from titration data, with values of Ks ranging from 9.97 × 103 to 1.28 × 102 M–1 in the decreasing order Pb2+ > Na+ > Cu2+ > Hg2+ > Cd2+. The stoichiometries found for 1–3 and 5 are in the range 1.85–2.09 and for 4 0.99–1.04. A 1H NMR spectroscopic study with selected metal ions exhibits significant spectral changes for the protons attached to the crown moiety; a few significant changes are also noted in the aromatic region. Among the ions studied, the highest change is observed with Na+ and Pb2+, whereas K+ does not show any significant change. The electrochemical study exhibits a significant cathodic shift of the oxidation potentials of the RuII centre in the presence of Na+ and Pb2+, thereby indicating complexation of these ions with the crown moiety. The electronic spectra, however, do not show significant spectral changes with various metal ions except for that of the ReI complex 6, which exhibits some change upon addition of Na+. The results obtained are presented and discussed in light of selectivity and intramolecular energy‐transfer.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
