Synthesis of 8-hydroxyquinoline functionalised DO3A ligand and Eu(III) and Er(III) complexes: Luminescence properties

The synthesis of a new DO3A-based macrocyclic ligand bearing a 8-hydroxyquinoline residue together with the prepn. of its Eu3+ and Er3+ neutral complexes are described. In a previous report [F. Rizzo, A. Papagni, F. Meinardi, R. Tubino, M. Ottonelli, G.F. Musso, G. Dellepiane, Synth. Met. 147 (2004) 143], we have shown that lanthanide complexes display very high stability combined with a good luminescence in aq. soln. under UV radiation, which indicate an energy transfer process from the excited 8-hydroxyquinoline moiety to the metal. In this work, we correlate the ability to transfer the energy from the sensitizer to lanthanide ion with pH behavior of the antenna. Furthermore, the variation of pH in Eu3+ complex supports the hypothesis of presence of charge-transfer transitions. The good soly. and sensitized emission in different solvents (org. and water) are very important aspects for their technol. applications as luminescent probes or NIR-emitting devices.