Stepwise Effective Molarities in Porphyrin Oligomer Complexes: Preorganization Results in Exceptionally Strong Chelate Cooperativity
Stepwise Effective Molarities in Porphyrin Oligomer Complexes: Preorganization Results in Exceptionally Strong Chelate Cooperativity
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DOI：
10.1021/ja209254r
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发表时间：
2011-12-28
影响因子：
15
通讯作者：
Anderson, Harry L.
中科院分区：
文献类型：
--
作者：
Hogben, Hannah J.;Sprafke, Johannes K.;Anderson, Harry L.
锌卟啉低聚物与多价配体的络合物可以通过加入大量过量的单齿配体如奎宁环来变性。我们已经使用变性滴定法来确定的环状锌卟啉六聚体与多齿配体与2至6个吡啶配位位点的配合物的稳定性。并对线型卟啉低聚物的配合物进行了研究。结果表明，第三至第六分子内配位事件与环状六聚体的阶梯有效摩尔浓度（EM）非常高（EM = 10（2）-10（3）M），而线性卟啉低聚物的值是适度的（EM接近0.05 M）。变性反应的形态配置文件表明，中间物种没有显着的人口和这些平衡是很好地描述了一个高度合作的两态模型。
Complexes of zinc porphyrin oligomers with multivalent ligands can be denatured by adding a large excess of a monodentate ligand, such as quinuclidine. We have used denaturation titrations to determine the stabilities of the complexes of a cyclic zinc-porphyrin hexamer with multidentate ligands with two to six pyridyl coordination sites. The corresponding complexes of linear porphyrin oligomers were also investigated. The results reveal that the stepwise effective molarities (EMs) for the third through sixth intramolecular coordination events with the cyclic hexamer are extremely high (EM = 10(2)-10(3) M), whereas the values for the linear porphyrin oligomers are modest (EM approximate to 0.05 M). The speciation profiles for the denaturation reactions demonstrate that intermediate species are not significantly populated and that these equilibria are well described by a highly cooperative two-state model.