Department of Inorganic, Analytical and Applied Chemistry, University of Geneva, 30 quai E. Ansermet, 1211 Geneva 4, Switzerland.
Chemistry. 2009 Nov 23;15(46):12719-32. doi: 10.1002/chem.200902026.
The replacement of terminal 2-benzimidazol-6-carboxypyridine (two internal rotational degrees of freedom) with 2-benzimidazol-8-hydroxyquinoline (one internal rotational degree of freedom) into segmental bis-tridentate ligands in going from L2 and L3-2 H to L12 b-2 H does not significantly affect the structures of the resulting binuclear lanthanide triple-stranded helical complexes Ln(2)(L2)(3), [Ln(2)(L3-2 H)(3)], and [Ln(2)(L12 b-2 H)(3)] (palindromic helices, intermetallic contact distance approximately 9 A, helical pitch approximately 1.4 nm per turn). However, their thermodynamic assemblies are completely different in solution, as evidenced by the spectacular decrease of the effective concentrations by two orders of magnitude for L12 b-2 H. This key parameter in the [Ln(2)(L12 b-2 H)(n)] (n=2, 3) complexes is further abruptly modulated along the lanthanide series (Ln=La to Lu), which provides an unprecedented tool for 1) tuning the number of ligand strands in the final helicates, 2) selectively coordinating lanthanides in the various complexes, and 3) controlling the ratio of lanthanide-containing polymers over discrete assemblies.
将末端 2-苯并咪唑-6-羧基吡啶（两个内部旋转自由度）替换为 2-苯并咪唑-8-羟基喹啉（一个内部旋转自由度），从 L2 和 L3-2H到 L12b-2H，作为分段双齿三齿配体，不会显著影响所得双核镧系元素三股螺旋配合物Ln(2)(L2)(3)、[Ln(2)(L3-2H)(3)]和[Ln(2)(L12b-2H)(3)]的结构（回文螺旋，金属间接触距离约为 9Å，每转螺旋螺距约为 1.4nm）。然而，它们在溶液中的热力学组装完全不同，这可以从L12b-2H的有效浓度显著降低两个数量级得到证明。这个关键参数在[Ln(2)(L12b-2H)(n)]（n=2,3）配合物中沿着镧系元素系列进一步急剧调节，这为 1）调节最终螺旋配合物中配体链的数量，2）选择性配位各种配合物中的镧系元素，3）控制含镧系元素聚合物与离散组装体的比例提供了前所未有的工具。
