Relationship between the analytical properties of Lanthanide(III) beta-diketonates and the nature of ligands

The effect of the nature of beta-diketones on the spectrochemical-luminesce nce properties of lanthanide complexes used as analytical forms for the hig hly sensitive determination of some rare-earth elements was examined. NMR s pectroscopy, molecular mechanics, calculations, and an experimental evaluat ion of the hydrophobicity of the test beta-diketones indicated that an incr ease in the intensity, quantum yield, and lifetime of luminescence of lanth anide (Ln) beta-diketonates depends on the charge distribution in the chela te ring, on the spatial structure, and on the hydrophobicity of the coordin ated ligand. These factors determine the efficiency of energy transfer from the beta-diketone to the Ln(+3) ion and the decrease in energy losses caus ed by the quenching action of water molecules.