Luminescent Properties of Europium(III), Gadolinium(III), and Terbium(III) Complexes with Alkyloxybenzoic Acids

Luminescent properties of europium(III), gadolinium(III), and terbium(III) complexes with 4-dodecyl- and 4-octadecyloxybenzoic acids were studied. Energies of excited triplet states of the acid anions (T₁) were determined from phosphorescence spectra of the Gd(III) complexes measured at 77 K. The luminescence mechanism found that intramolecular energy transfer from the organic ligand to the lanthanide ion was effective for the Eu(III) complexes. Complexes of composition LnL₃Phen, where Phen is 1,10-phenanthroline, were prepared to increase the luminescence intensity of the Tb(III) complexes. Experimental spectra showed that the integrated luminescence intensity of Tb³⁺ in TbL₃Phen increased as compared with TbL₃.