• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Chemistry: A European journal >Definition of an intramolecular Eu-to-Eu energy transfer within a discrete [Eu _2L] complex in solution
【24h】

Definition of an intramolecular Eu-to-Eu energy transfer within a discrete [Eu _2L] complex in solution

机译：溶液中离散[Eu _2L]配合物中分子内Eu-Eu能量转移的定义

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

Ligand L, based on two do3a moieties linked by the methylene groups of 6,6'-dimethyl-2,2'-bipyridine, was synthesized and characterized. The addition of Ln salts to an aqueous solution of L (0.01 M Tris-HCl, pH 7.4) led to the successive formation of [LnL] and [Ln _2L] complexes, as evidenced by UV/Vis and fluorescence titration experiments. Homodinuclear [Ln _2L] complexes (Ln=Eu, Gd, Tb, Yb, and Lu) were prepared and characterized. The ~1H and ~(13)C NMR spectra of the Lu and Yb complexes in D _2O solution (pD=7.0) showed C _1 symmetry of these species in solution, pointing to two different chemical environments for the two lanthanide cations. The analysis of the chemical shifts of the Yb complex indicated that the two coordination sites present square antiprismatic (SAP) coordination environments around the metal ions. The spectroscopic properties of the [Tb _2L] complex upon ligand excitation revealed conventional behavior with τ _(H2O)=2.05(1) ms and φ _(H2O)=51 %, except for the calculation of the hydration number obtained from the luminescent lifetimes in H _2O and D _2O, which pointed to a non-integer value of 0.6 water molecules per Tb ~(III) ion. In contrast, the Eu complex revealed surprising features such as: 1) the presence of two and up to five components in the ~5D _0→ ~7F _0 and ~5D _0→ ~7F _1 emission bands, respectively; 2) marked differences between the normalized spectra obtained in H _2O and D _2O solutions; and 3) unconventional temporal evolution of the luminescence intensity at certain wavelengths, the intensity profile first displaying a rising step before the occurrence of the expected decay. Additional spectroscopic experiments performed on [Gd _(2-x)Eu _xL] complexes (x=0.1 and 1.9) confirmed the presence of two distinct Eu sites with hydration numbers of 0 (site I) and 2 (site II), and showed that the unconventional temporal evolution of the emission intensity is the result of an unprecedented intramolecular Eu-to-Eu energy-transfer process. A mathematical model was developed to interpret the experimental data, leading to energy-transfer rates of 0.98 ms ~(-1) for the transfer from the site with q=0 to that with q=2 and vice versa. Hartree-Fock (HF) and density functional theory (DFT) calculations performed at the B3LYP level were used to investigate the conformation of the complex in solution, and to estimate the intermetallic distance, which provided F?rster radii (R _0) values of 8.1 ? for the energy transfer from site I to site II, and 6.8 ? for the reverse energy transfer. These results represent the first evidence of an intramolecular energy-transfer equilibrium between two identical lanthanide cations within a discrete molecular complex in solution.
机译：合成并表征了基于两个通过6,6'-二甲基-2,2'-联吡啶的亚甲基连接的do3a部分的配体L。将Ln盐添加到L的水溶液（0.01 M Tris-HCl，pH 7.4）中会导致[LnL]和[Ln _2L]复合物的连续形成，这通过UV / Vis和荧光滴定实验得以证明。制备并表征了同核核[Ln _2L]复合物（Ln = Eu，Gd，Tb，Yb和Lu）。 D _2O溶液（pD = 7.0）中Lu和Yb配合物的〜1H和〜（13）C NMR光谱显示了这些物质在溶液中的C _1对称性，指出了两种镧系元素阳离子的两种不同化学环境。对Yb络合物的化学位移的分析表明，两个配位点在金属离子周围呈现方形反棱角（SAP）配位环境。配体激发后[Tb _2L]配合物的光谱性质显示了常规行为，其中τ_（H2O）= 2.05（1）ms和Φ_（H2O）= 51％，除了计算从发光获得的水合数H _2O和D _2O的寿命，表明每个Tb〜（III）离子的非整数值为0.6水分子。相反，Eu络合物显示出令人惊讶的特征，例如：1）在〜5D _0→〜7F _0和〜5D _0→〜7F _1发射带中分别存在两个和多达五个组分; 2）在H _2O和D _2O溶液中获得的归一化光谱之间存在明显差异; 3）在某些波长下发光强度的非常规时间演变，强度分布在预期衰减发生之前首先显示出上升步骤。对[Gd _（2-x）Eu _xL]络合物（x = 0.1和1.9）进行的其他光谱实验证实，存在两个不同的Eu位点，其水合数分别为0（位点I）和2（位点II），并显示发射强度的非常规时间演变是前所未有的分子内Eu-Eu-Eu能量转移过程的结果。建立了数学模型来解释实验数据，从而导致能量转移速率为0.98 ms〜（-1），以便从q = 0的位置向q = 2的位置转移，反之亦然。在B3LYP水平上进行的Hartree-Fock（HF）和密度泛函理论（DFT）计算用于研究溶液中复合物的构象，并估计金属间距离，从而提供Frster半径（R _0）的值。 8.1？从站点I到站点II的能量传输，以及6.8？用于反向能量传递。这些结果代表了溶液中离散分子复合物中两个相同镧系元素阳离子之间分子内能量转移平衡的第一个证据。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号