The Molecular Structures and Properties of Novel Eu(III) Complexes with Asymmetric Bis-phosphine Oxides
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0965-S03-12
The Molecular Structures and Properties of Novel Eu(III) Complexes with Asymmetric Bis-phosphine Oxides Hiroki Iwanaga, Fumihiko Aiga, and Akio Amano Corporate Research & Development Center, TOSHIBA Corporation, 1, Komukai-Toshiba-cho, Saiwaiku, Kawasaki, 212-8582, Japan
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. INTRODUCTION Recently, there has been a great need for red fluorescence compounds to realize white LED (Light Emitting Diode) devices with large luminance and large color rendering indexes. On the other hand, Eu(III) complexes have attracted a great deal of attention because they have the potential for application in many electronic devices, such as LED devices, and are considered to be useful as laser materials and security inks [1,2]. Eu(III) complexes for application in LED devices must have large solubility and large emission intensity excited at near-ultraviolet light, which is the maximum wavelength of LED-chips in general use. The following three types of Eu(III) complexes have been the subjects of numerous reports. Eu(III) complexes with βdiketones (type 1) are relatively soluble but they cannot be excited efficiently at near-ultraviolet light due to small absorption coefficient. Eu(III) complexes with β-diketones and 1,10phenanthroline (type 2) are almost insoluble because they have large plain condensed rings. On the other hand, Eu(III) complexes with β-diketones and phosphine oxides (type 3) are relatively soluble and can be excited at near-ultraviolet light. However, the solubility was not large enough for application in LED devices [3, 4]. We have reported that Eu(III) complexes with two different phosphine oxides can be excited efficiently at near-ultraviolet light. Eu(III) complexes of this type are highly soluble even in a fluorinated solvent and have sufficient solubility for practical use in LED devices [3-6]. With a view to achieving larger emission intensity, this paper discusses novel Eu(III) complexes with asymmetric bis-phosphine oxide.
EXPERIMENT Measurement of solubility Saturated solutions were obtained by adding a solvent to an excess amount of Eu(III) complexes at 20 , shaking the mixture thoroughly, allowing it to stand for a week, and then passing it through a 0.2 µm filter. Concentration of Eu(III) ions of a saturated solution was determined by ICP-MS using an SII Nano Technology SPS1200AR.
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