Fluorescence Enhancement by Electron-Withdrawing Groups on β-Diketones in Eu(III)-β-diketonate-topo Ternary Complexes

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Europium(III) complexes with two series of β-diketonates and trioctylphosphine oxide (topo) have been synthesized and the fluorescence properties were studied. The β-dikatonate ligands used had the formula R<sub>1</sub>COCHCOR<sub>2</sub> (I: R<sub>1</sub>=2- naphthyl, R<sub>2</sub>=CF<sub>3</sub>, CF<sub>2</sub>CF<sub>3</sub>, CF<sub>2</sub>CF<sub>2</sub>CF<sub>3</sub>, CF<sub>2</sub>CF<sub>2</sub>CF<sub>2</sub>CF<sub>3</sub>; II: R<sub>1</sub>=2-phenanthryl, R<sub>2</sub>=CF<sub>3</sub>, CF<sub>2</sub>CF<sub>3</sub>, CF<sub>2</sub>CF<sub>2</sub>CF<sub>3</sub>, CF<sub>2</sub>CF<sub>2</sub>CF<sub>2</sub>CF<sub>3</sub>, which are designated as NF<sub>3</sub>, NF<sub>5</sub>, NF<sub>7</sub>, NF<sub>9</sub>, PF<sub>3</sub>, PF<sub>5</sub>, PF<sub>7</sub> and PF<sub>9</sub>, respectively). These complexes having the composition of [Eu(L)<sub>3</sub>(topo)<sub>2</sub>] (L=NF<sub>3</sub>-NF<sub>9</sub>, PF<sub>3</sub>) and [Eu(L) <sub>3</sub>(topo)<sub>1.5</sub>] (L=PF<sub>5</sub>-PF<sub>9</sub>) gave very strong fluorescence emission when excited by UV light (complexes of NF<sub>3</sub>-NF<sub>9</sub>, λ<sub>ex, max</sub>=339nm, λ<sub>em, max</sub>=615nm, PF<sub>3</sub>, λ<sub>ex, max</sub>=344nm, λ<sub>em, max</sub>=615nm, PF<sub>5</sub>-PF<sub>9</sub>, λ<sub>ex, max</sub>=346nm, λ<sub>em, max</sub>=615nm). The ultra-violet spectra, fluorescence spectra, molar absorption coefficient (ε), fluorescence quantum yield (φ<sub>f</sub>), and fluorescence lifetime (τ) of the complexes in benzene were measured. The results reveal tendencies for φ<sub>f</sub> and the fluorescence absolute sensitivity (A.S=εφ<sub>f</sub>) in the following order: φ<sub>f</sub>, 2-naphthyl>2-phenanthryl(for an identical R<sub>2</sub>); C<sub>4</sub>F<sub>9</sub>≥C<sub>3</sub>F<sub>7</sub>>C<sub>2</sub>F<sub>5</sub>>CF<sub>3</sub>(for an identical R<sub>1</sub>); A.S, PF<sub>9</sub>>PF<sub>7</sub>>NF<sub>9</sub>≈NF<sub>7</sub>>PF<sub>5</sub>≈NF<sub>5</sub>>NF<sub>3</sub>>PF<sub>3</sub>. The <sup>1</sup>H NMR signal of β-H in the β-diketonate ligand turns out to be a good measure to estimate φ<sub>f</sub>; since the R<sub>2</sub> is more electron-withdrawing, the β-H chemical shift goes to a higher field and the fluorescence of the complex becomes more enhanced. The detection limit of the complex [Eu(L)<sub>3</sub>(topo)<sub>1.5</sub>] (L=PF<sub>7</sub>) is 4.42×10<sup>-12</sup>M (M=mol dm<sup>-3</sup>).

収録刊行物

  • Analytical sciences : the international journal of the Japan Society for Analytical Chemistry  

    Analytical sciences : the international journal of the Japan Society for Analytical Chemistry 12(1), 31-36, 1996-02-10 

    The Japan Society for Analytical Chemistry

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各種コード

  • NII論文ID(NAID)
    10002407334
  • NII書誌ID(NCID)
    AA10500785
  • 本文言語コード
    ENG
  • 資料種別
    ART
  • ISSN
    09106340
  • データ提供元
    CJP書誌  J-STAGE 
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