No abstract

The density functional theory was employed to investigate Eu(III) complexes with three beta-diketonates and two phosphine oxides (complex M1: Eu(bdk)3(TPPO)2, complex M2: Eu(bdk)3(TMPO)2, and complex M3: Eu(bdk)3(TPPO)(TMPO)) deemed to be the model complexes of the fluorescence compounds for the ultraviolet LED devices we have recently developed. For each complex, two minimum energy points corresponding to two different optimized geometries (structures A and B) have been found, and the difference of the energy between two minimum energy points is found to be quite small (less than 1 kcal/mol). Vertical excitation energies and oscillator strengths for each complex at two optimized geometries have been obtained by the time-dependent density functional theory, and the character of the excited states has been investigated. For complex M3, the absorption edge is red-shifted, and the oscillator strengths are relatively large. The efficiency of intersystem crossing and energy transfer from the triplet excited state to the Eu(III) ion is considered by calculating DeltaE(ISC) (the energy difference between the first singlet excited state and the first triplet excited state) and DeltaE(ET) (the difference between the excitation energy of the complex for the first triplet excited state and the emission energy of the Eu(III) ion for 5D to 7F).

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.

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.

Potentiometric creatinine microsensors were fabricated by use of a composite film consisting of polyion complex (PlC), which contains creatinine iminohydrolase (CIH), and the electrochemically inactive polypyrrole (iPPy). The PPy/PIC-CIH composite film electrode displayed potential response to creatinine concentration owing to a pH change occurring during the enzymatic reaction. The sensitivity was varied by using different polyions of the PlC. With poly-Llysine and sebacic acid, the iPPy/PIC-CIH electrode demonstrated a high sensitivity (29.8 mV decade') and a low detection limit (1 X 106 mol dm3), which allow one to monitor creatinine concentration in the physiological range.* Electrochemical Society Active Member.