Synthesis and luminescent properties of supramolecules of beta-diketonate of Eu(III) and crown ethers as ligands

摘要

This work reports the synthesis and luminescence behavior of the diaquatris(thenoyltrifluoracetonate)europium(III) with dibenzo 18-crown-6 (DB18C6) and 18-crown-6 (18C6), in the solid state. The new compounds Eu(TTA)(3)(H2O)(2)(DB18C6)(2) and Eu(TTA)(3)(H2O)(2)(18C6)(2) were characterized by elemental analysis, infrared spectroscopy, th.ermalanalysis and scattering electronic microscopy. The emission spectra show narrow emission bands that arise from the D-5(0) --> F-7(0) transitions (J = 0-4) of the Eu3+ ion. The spectral data of the Eu(TTA)(3)(H2O)(2)(DB18C6)(2) and Eu(TTA)(3)(H2O)(2)(18C6)(2) compounds present, respectively, one and two peaks assigned to the D-5(0) --> F-7(0) transition (similar to 578 nm), suggesting one and two sites of symmetry around the metal ion. In addition, the luminescence decay curves of these DB18C6 and 18C6 systems were better fitted by a mono- and bi-exponential decays, respectively. The values of the experimental intensity parameters (Omega(lambda)) indicate that the europium ion in the complexes is in a highly polarizable chemical environment. The values of emission quantum efficiencies for the two Eu(Ill)-supramolecular compounds are similar (eta = 26%). (C) 2003 Elsevier Science (USA). All rights reserved. [References: 18]