Intra-Complex Energy Transfer of Europium(III) Complexes Containing Anthracene and Phenanthrene Moieties

Laser excitation and luminescence studies were carried out for an ethanol solution of tris(hexafluoroacetylacetonato)europium(III), Eu(hfac)3(H2O)2 (1), and n-hexane solutions of tris(hexafluoroacetylacetonato)europium(III) bis(9-diisopropylphosphorylanthracene), Eu(hfac)3(DiPAnO)2 (2), and tris(hexafluoroacetylacetonato)europium(III) bis(2-diisopropylphosphorylphenanthrene), Eu(hfac)3(DiPPheO)2 (3). The absorption spectra of 2 and 3 in n-hexane are interpreted by assuming that the central Eu(III) ion weakly interacts with the DiPAnO and DiPPheO moieties. The emission spectroscopic studies revealed that (1) Eu(hfac)3(DiPAnO)2 emitts only fluorescence from the DiPAnO moiety and (2) Eu(hfac)3(DiPPheO)2 gives luminescence from the central Eu(III) ion, and (3) Eu(hfa)3(H2O)2 and Eu(hfac)3(DiPPheO)2 afford emission from both the 5D1 and 5D0 states of the Eu(III) ion upon 355 nm laser excitation. The intracomplex energy transfer processes are presented on the basis of absorption, emission and laser excitation studies.