Spectral-Luminescent Properties of Mixed-Ligand Europium(III) Complexes with O-Methoxybenzoic Acid and Phosphorus-Containing Neutral Ligands

The spectral-luminescent properties of europium(III) complexes with o-methoxybenzoic acid and phosphorus-containing neutral ligands with an island structure and the compositions Eu(MOBA)₃ · 3H₂O and Eu(MOBA)₃ · L, where MOBA is o-methoxybenzoic acid and L is hmpa (hexamethylphosphortriamide, tppo (triphenylphosphinoxide), and Et₆pa (hexaethylphosphortriamide), are studied. It is found that the excitation energy transfer to the europium ion occurs from the levels of both o-methoxybenzoic acid and phosphorus-containing neutral ligands. The electronic absorption and luminescence excitation spectra, as well as the Stark structure of the ⁵D₀−⁷F_j ( j = 0–2) electronic transitions in the luminescence spectra of mixed-ligand complexes of europium(III) o-methoxybenzoates, are analyzed. The highest luminescence intensity is demonstrated by europium(III) methoxybenzoate with triphenylphosphinoxide.