Study of Molecular Structures and Properties of Europium(III) Complexes with Phosphine Oxides by NMR Analysis

Abstract

The 31P-NMR spectra of europium complexes with β-diketones and phosphine oxides in CDCl3, DMSO-d 6, toluene-d 8 with dissolved fluorinated polymers, and fluorinated solvent were investigated as well as the temperature dependence of these spectra. When a mixture of europium complex 1 and 1.0 molar equivalent of trioctylphosphine oxide and triphenylphosphine oxide was dissolved in a fluorinated solvent, europium complex 2 with two types of phosphine oxides was formed at room temperature. In CDCl3 and toluene-d 8 solutions, however, this complex was identified only at low temperatures. This difference is thought to be due to the differences in the speed of ligand exchanges. In DMSO-d 6 solution, no signal corresponding to the europium complex with phosphine oxides was observed. This implies that the major portion of phosphine oxides is not coordinated with europium ions in DMSO-d 6 solution. The fluorescence intensity of each europium complex in a solvent was correlated to the solvent and the 31P-NMR spectrum. It was found that the fluorescence intensity was the highest in the fluorinated solvent.

Synthesis and evaluation of the europiumIII and zincII complexes as luminescent bioprobes in high content cell-imaging analysis

“…Clearly, this is the only form that exists in DMSO for compound 5. Similar results were reported for europium (III) complexes with phosphine oxides in DMSO-d 6 [32]. However, complex 7 showed a remarkable stability in comparison to 5 and 6 in a deuterated DMSO-D 2 O solvent mixture.…”

Emission Properties, Solubility, Thermodynamic Analysis and NMR Studies of Rare-Earth Complexes with Two Different Phosphine Oxides

“…However, ligand exchange of phosphine oxide ligands was detected by 31 P-NMR analysis [ 20 ]. Ligand exchange was expected to have an undesirable effect on the durability and emission intensity of Eu(III) complexes.…”

Novel Tb(III) complexes with two different structures of phosphine oxides and their properties

“…2,3-dihydrodecafluoropentane was selected for the measurements of solubilities as a solvent because it is useful for predicting rareearth complexes dissolvable in a fluorinated polymer at supersaturated high concentrations [25]. Fluorinated polymers are suitable for matrix polymers of Eu(III) complexes used as fluorescence layers of LED devices [14].…”

“…Among hydrophobic solvents, compared with hexane, it was found to be very hard for 2,3-dihydrodecafluoropentane to solve Eu(III) complexes [25]. However, among the solvents, emission intensity of Eu(III) complexes was the highest when dissolved into a 2,3-dihydrodecafluoropentane, indicating fluorinated polymer is suitable for obtaining large emission [14]. Rare-earth complexes are dissolved into many kinds of solvents and polymers with high concentrations for use in various applications.…”

“…The increased asymmetry of molecular structures was found to be effective for increasing solubility and emission intensity. However, ligand exchange of phosphine oxide that was expected to have an undesirable effect on emission intensity and durability was detected by 31 P-NMR analysis [14]. Therefore, we established the second molecular design, namely, two phosphine oxide ligands are tied together and bis-phosphine oxide structure is introduced to an Eu(III) ion in order to prevent ligand exchange due to the chelate effect [15].…”