The Molecular Structures and Properties of Novel Eu(III) Complexes with Asymmetric Bis-phosphine Oxides

Abstract

Several novel Eu(III) complexes with asymmetric bis-phosphine oxide- ligands were synthesized. The relation between molecular structures of bis-phosphine- oxide ligands and properties of Eu(III) complexes was investigated and some interesting results were obtained. Solubility of Eu(III) complexes in fluorinated medium and silicone oil were strongly dependent on the length of alkyl chain (n) binding two phosphine oxide- parts. Also, the thermal properties of Eu(III) complexes were correlated to the solubility. Eu(III) complex 6(n=3), which has phenyl and n-octyl groups as the substituents of a bis-phosphine oxide- ligand, was found to be highly soluble and have large fluorescence intensity.

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

“…The second molecular design involves two different phosphine oxides, which are tied together, and the introduction of a bis-phosphine oxide structure to a rare-earth ion in order to prevent ligand exchange, which is due to the chelate effect, as shown in Figure 2 [ 21 ].…”

“…Non-symmetric bis-phosphine oxide 11 was synthesized and mixed with 1.0 molar equivalent of Eu(III) complex 1 in fluorinated solvent, as shown in Figure 9 [ 21 ]. The emission spectrum of the solution is shown in Figure 9 , together with that of a mixture of 1 and 1.0 molar equivalent of TPPO and TOPO.…”

“…The signals of the 31 P NMR spectrum for the mixture of Eu(III) complex 1 and non-symmetric bis-phosphine oxide 11 are very sharp and are shifted toward upper magnetic fields from the original ones of 11 , suggesting that all the non-symmetric bis-phosphine oxide 11 coordinated with Eu(III) ion without ligand exchange, and that Eu(III) complex 12 was formed in the solution ( Figure 10 ) [ 21 ]. The larger emission intensity of the mixture of 1 and 11 shown in Figure 9 is due to the formation of Eu(III) complex 12 , in which two different phosphine oxide structures are coordinated perfectly to one Eu(III) ion.…”

“…Several novel Eu(III) complexes with non-symmetric bis-phosphine oxides were synthesized ( Figure 11 ) and their melting points, thermodynamic properties, and solubilities in 2,3-dihydrodecafluoropentane were investigated ( Table 2 ) [ 21 ]. The sum of the enthalpy of fusion and phase transition (Δ H (SUM) ) is the heat capacity that is required to change the definite amount of crystals of an Eu(III) complex located at room temperature into amorphous solid; this sum, from the results of dichroic dyes, is known to be correlated with the solubility [ 25 , 26 ].…”

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

“…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]. The molecular structure of bis-phosphine oxide is designed to be asymmetric on the analogy of the Eu(III) complexes with two different phosphine oxides to attain large solubility and emission intensity.…”