Modification of the Luminescence Properties of an Europium(III)Tris(beta-diketonate)Complex by Inclusion in gamma-cyclodextrin and 2,3,6-trimethyl-gamma-cycIodextrin

摘要

A 1:1 inclusion compound between octakis(2,3,6-tri-O-methyl)-gamma-cyclodextrin(TRIMEG)and the chelate complex Eu(NTA)_3 centre dot 2H_2O(NTA=l-(2-naphthoyl)-3,3,3-trifluoroacetonate)was prepared and characterized by powder X-ray diffraction,thermogravimetric analysis and photoluminescence spectroscopy.The results were compared with those obtained for the corresponding native gamma-CD adduct.Excitation and emission spectra were measured,and the lifetimes were determined for the Eu~(3+)first excited state(~5D_0).The results indicate the presence of only one low-symmetry environment for the Eu~(3+)cations in the inclusion compounds.Encapsulation of the Europium complex in the two CDs increases the quantum efficiency of the ligand-to-metal energy transfer pathway,but the efficiency of the Eu~(3+)sensitization was significantly higher with TRIMEG as the host molecule.This may be related with the observation that the two hosts appear to have different influences on the Eu~(3+)coordination environments for the guest molecule.