Miecznikowski John R, Jasinski Jerry P, Kaur Manpreet, Bonitatibus Sheila C, Almanza Emilse M, Kharbouch Rami M, Zygmont Samantha E, Landy Kendra R
Department of Chemistry and Biochemistry, Fairfield University;
Department of Chemistry, Keene State College.
J Vis Exp. 2020 Mar 19(157). doi: 10.3791/60668.
Chemical model complexes are prepared to represent the active site of an enzyme. In this protocol, a family of tridentate pincer ligand precursors (each possessing two sulfur and one nitrogen donor atom functionalities (SNS) and based on bis-imidazole or bis-triazole compounds) are metallated with CoCl2·6H2O to afford tridentate SNS pincer cobalt(II) complexes. Preparation of the cobalt(II) model complexes for liver alcohol dehydrogenase is facile. Based on a quick color change upon adding the CoCl2·6H2O to acetonitrile solution that contains the ligand precursor, the complex forms rapidly. Formation of the metal complex is complete after allowing the solution to reflux overnight. These cobalt(II) complexes serve as models for the zinc active site in liver alcohol dehydrogenase (LADH). The complexes are characterized using single crystal X-ray diffraction, electrospray mass spectrometry, ultra-violet visible spectroscopy, and elemental analysis. To accurately determine the structure of the complex, its single crystal structure must be determined. Single crystals of the complexes that are suitable for X-ray diffraction are then grown via slow vapor diffusion of diethyl ether into an acetonitrile solution that contains the cobalt(II) complex. For high quality crystals, recrystallization typically takes place over a 1 week period, or longer. The method can be applied to the preparation of other model coordination complexes and can be used in undergraduate teaching laboratories. Finally, it is believed that others may find this recrystallization method to obtain single crystals beneficial to their research.
制备化学模型配合物以代表酶的活性位点。在本实验方案中，一系列三齿钳形配体前体（每个都具有两个硫和一个氮供体原子官能团（SNS），基于双咪唑或双三唑化合物）与CoCl₂·6H₂O进行金属化反应，得到三齿SNS钳形钴（II）配合物。制备用于肝脏乙醇脱氢酶的钴（II）模型配合物很简便。基于向含有配体前体的乙腈溶液中加入CoCl₂·6H₂O后快速的颜色变化，配合物迅速形成。使溶液回流过夜后，金属配合物的形成完成。这些钴（II）配合物可作为肝脏乙醇脱氢酶（LADH）中锌活性位点的模型。使用单晶X射线衍射、电喷雾质谱、紫外可见光谱和元素分析对配合物进行表征。为了准确确定配合物的结构，必须确定其单晶结构。然后通过将乙醚缓慢气相扩散到含有钴（II）配合物的乙腈溶液中来生长适合X射线衍射的配合物单晶。对于高质量的晶体，重结晶通常需要1周或更长时间。该方法可应用于制备其他模型配位配合物，并可用于本科教学实验室。最后，相信其他人可能会发现这种获得单晶的重结晶方法对他们的研究有益。
