Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, USA.
J Am Chem Soc. 2009 Dec 9;131(48):17620-9. doi: 10.1021/ja906474z.
We report herein the synthesis and metal complexation properties of two macrocyclic hosts that contain two 2,2'-bipyridines and two urea groups. These hosts take advantage of the conformationally mobile 5,5'-positions of the bipyridines to give metal binding sites that are dynamic. By simple bond rotation, these hosts can exchange an interior (endo) situated metal binding site for an exterior (exo) binding site. We examine the solid-state structures of the two free hosts and two coordination complexes ([Cd(host 1)(H(2)O)(NO(3))(2)] and Ag(2)(host 2)(2)) using X-ray crystallography. Analysis of these crystal structures suggests that the bipyridine groups within the hosts are able to rotate to access multiple conformations including the desired exo and endo conformations. We also investigate the binding affinity of these new ligands in solution by UV-vis titrations with a series of metal nitrate salts (Ag, Cd, Zn, Ni, Mn, Fe, Co, Cr, and Cu) to afford discrete metal complexes. Some complexes showed a slow subsequent assembly to yield coordination polymers. Thus, these systems may afford unique insights into the process of metal organic framework formation.
我们在此报告了两种大环主体的合成和金属络合性质，它们包含两个 2,2'-联吡啶和两个脲基。这些主体利用联吡啶的 5,5'-位的构象可动性，提供了动态的金属结合位点。通过简单的键旋转，这些主体可以将内部（内）定位的金属结合位点交换为外部（外）结合位点。我们使用 X 射线晶体学研究了两个游离主体和两个配位配合物（[Cd(host 1)(H(2)O)(NO(3))(2)]和Ag(2)(host 2)(2)）的固态结构。这些晶体结构的分析表明，主体内的联吡啶基团能够旋转以获得多种构象，包括所需的外和内构象。我们还通过一系列硝酸盐盐（Ag、Cd、Zn、Ni、Mn、Fe、Co、Cr 和 Cu）的紫外可见滴定法在溶液中研究了这些新配体的结合亲和力，以获得离散的金属配合物。一些配合物显示出随后缓慢组装以生成配位聚合物。因此，这些系统可能为金属有机骨架形成过程提供独特的见解。
