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首页> 外文期刊>Chemistry: A European journal >The First Sellf-Assembled Trimetallic Lanthanide Helicates Driven by Positive Cooperativity
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The First Sellf-Assembled Trimetallic Lanthanide Helicates Driven by Positive Cooperativity

机译：积极合作推动了首批塞夫组装三金属镧系元素螺旋

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The segmental tris-tridentate ligand L7 reacts with stoichiometric quantities of Ln~III (Ln=La-Lu) in acetonitrile to give the complexes [Ln_2(L7)_3]~(6+) and [Ln_3(L7)_3]~(9+). Formation constants point to negligible size-discriminating effects along the lanthanide series, but Scatchard plots suggest that the self-assembly of the trimetallic triple-stranded helicates [Ln_3(L7)_3]-(CF_3SO_3)_9 (Ln=La, Eu, Gd, Tb, Lu) and the X-ray crystal structure of [Eu_3(L7)_3](CF_3SO_3)_9 centre dot (CH_3CN)_9 centre dot (H_2O)_2 (3u_3(L7)_3](CF_3SO_3)_9 centre dot (CH_3CN)_9 centre dot (H_2O)_2 (Eu_3C_216H_226N_48O_35F_27S_9, triclinic, P1, Z=2) shows the three ligand strands warpped around a pseudo-threefold axis defined by the three metal ions rigidly held at about 9 A. Each metal ion is coordinated by nine donor atoms in a pseudo-trigonal prismatic arrangement, but the existence of terminal carboxy-amide uits in the ligand strands differentiates the electronic properties of the terminal and the central metallic sites. Photophysical data confirm that the three coordination sites possess comparable pseudo-trigonal symmetries in the solid state and in solution. High-resolution luminescence analyses evidence a low-lying LMCT state affecting the central EuN_9 iste, so that multi-metal-centered luminescence is essentially dominated by the emission from the two terminal EuN_6O_3 sites in [Eu_3(L7)_3]~(9+). New multicenter equations have been developed for investigating the solution structure of [Ln_3(L7)_3]~(9+) by paramagnetic NMR spectroscopy and linear correlations for Ln=Ce-Tb imply isostructurality for these larger lanthanides. NMR spectra point to the triple helical structure being maintained in solution, but an inversion of the magnitude of the second-rank crystal-field parameters, obtained by LIS analysis, for the LnN_6O_3 and LnN_9 sites with respect to the parameters extracted for Eu~III from luminescence data, suggests that the geometry of the central LnN_9 site is somewhat relaxed in solution.
机译：分段三三齿配体L7与化学计量量的Ln〜III（Ln = La-Lu）在乙腈中反应，生成配合物[Ln_2（L7）_3]〜（6+）和[Ln_3（L7）_3]〜（ 9岁以上）。形成常数指向沿镧系的尺寸区分作用可忽略不计，但是Scatchard图表明三金属三链螺旋结构[Ln_3（L7）_3]-（CF_3SO_3）_9（Ln = La，Eu，Gd）的自组装，Tb，Lu）和[Eu_3（L7）_3]（CF_3SO_3）_9中心点（CH_3CN）_9中心点（H_2O）_2（3u_3（L7）_3]（CF_3SO_3）_9中心点（ CH_3CN）_9中心点（H_2O）_2（Eu_3C_216H_226N_48O_35F_27S_9，三斜晶系，P1，Z = 2）显示了围绕由刚性固定在约9 A的三种金属离子所定义的拟三倍轴弯曲的三根配体链。由九个供体原子按伪三角棱柱排列排列，但是配体链中末端羧基酰胺化合物的存在将末端和中心金属位点的电子性质区分开来。光物理数据证实这三个配位点具有可比拟的伪位点。固态和溶液中的三角形对称性。发光分析表明，低层的LMCT状态会影响EuN_9的中心中心，因此多金属中心的发光主要由[Eu_3（L7）_3]〜（9+）的两个末端EuN_6O_3位置的发射决定。已开发出新的多中心方程，用于通过顺磁NMR光谱研究[Ln_3（L7）_3]〜（9+）的溶液结构，Ln = Ce-Tb的线性相关意味着这些较大的镧系元素的同构性。 NMR光谱指出溶液中保持了三重螺旋结构，但是相对于从Eu〜III中提取的参数，通过LIS分析获得的LnN_6O_3和LnN_9位的第二级晶体场参数的大小反转从发光数据可以看出，中央LnN_9位点的几何形状在溶液中有些松弛。

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