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)$_3$ $\cdot$ 3Н$_2$О и Eu(MOBA)$_3$ $\cdot$ $L$, where MOBA is o-methoxybenzoic acid and $L$ is hmpa (hexamethylphosphortriamide, tppo (triphenylphosphinoxide), and Et$_6$pa (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 $^5D_0-{}^7F_{j}$ ($j$ = 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.