Abstract: The 1, 10-phenanthroline-aromatic carboxylic acid (benzoic acid and o-phthalic acid) binary and ternary complexes of europium were synthesized. The fluorescence and FT-IR spectroscopy, elemental analysis, UV spectroscopic studies on these complexes were also performed. These complexes can emit strong red fluorescence of Eu(Ⅲ) excited by UV light. At the same excited wavelength, the fluorescence spectra of the complexes were also studied. The results indicated that the fluorescence intensities of ternary complexes are stronger than that of binary complexes. The reason is that phenanthroline has higher electron density and higher orbit scope in the conjugated system and consequently an easier energy transfer to the europium ion, which makes the fluorescence intensity of ternary complexes be stronger than that of binary complexes.

Key words:  complexes of europium; o-phthalic acid; benzoic acid; 1, 10-phenanthroline; fluorescence spectra