Mixed 8-oxyquinolinecalix[4]arene/phenanthroline receptors as luminescence sensors for zinc(II) ions

The luminescence behavior of bis-(8-oxyquinoline)calix[4]arene is practically centered on the quinoline chromophore, but involves efficient energy transfer from the calix[4]arene moiety. In the presence of Zn2+ ions, coordination of the quinoline groups is observed, leading to characteristic changes in the absorption, fluorescence and NMR spectra. Energy transfer from the calix[4]arene moiety is precluded by the coordination of the Zn2+ ions. In the resulting complex, a significant decrease in the emission quantum yields takes place. However, by incorporating an additional batho-phenanthroline ligand, a great emission enhancement has been detected, revealing the occurrence of synergistic effects in the bis-(8-oxyquinoline)calix[4]arene(batho-phenanthroline)zinc(II) complex.