Expanded Porphyrins - A New Approach to the Generation of Multi-centered Catalysts

许多生物学上重要的酶含有两个或多个过渡金属中心。到目前为止，已经投入了大量的努力来模拟这些酶的活性位点，并且已经研究了依赖于含有两个或更多个配位部分的配体的许多络合物。然而，支持形成双核或多核配合物的大环配体的数量是有限的。这种配体系统的优点包括它们的刚性潜力，它们在单个金属中心周围稳定特定构型的能力，以及它们强制限定金属-金属距离的能力。因此，它们可以支持新结构基序的形成。氧化还原活性双核配合物的另一个吸引人的方面是它们可以支持多电子氧化还原过程的事实，这是一个可以与良好效果结合的特征，具有将两个反应伴侣紧密靠近的能力。在Jonathan Sessler教授小组的博士后研究期间，将制备和研究寡吡咯卟啉型配体的双核和多核络合物，即所谓的“扩展卟啉”，作为酶模拟物。这些系统将检查其复杂的底物相互作用和催化活性在氧化酶和水解酶样反应。特别感兴趣的是烯丙醇的环氧化和酯和酰胺的催化裂解。

Many biologically important enzymes contain two or more transition metal centers. To date, much effort has been devoted to the modeling of the active sites of these enzymes and many complexes have been investigated which rely on ligands containing two or more coordinating moieties. However, the number of macrocyclic ligands which support the formation di- or polynuclear complexes is limited. The advantages of such ligand systems include their potential for rigidity, their ability to stabilize a particular configuration around the individual metal centers, and their capacity to enforce defined metal¿metal distances. As such, they could support the formation of new structural motifs. A further attractive aspect of redox active dinuclear complexes is the fact they could support multi-electron redox processes, a feature that could be combined with good effect with an ability to position two reaction partners in close proximity. During the proposed postdoctoral stay in the group of Prof. Jonathan Sessler di- and multinuclear complexes of oligopyrrolic porphyrin-type ligands, so-called ¿expanded porphyrins¿, will be prepared and investigated as enzyme mimics. These systems will be examined with regard to their complex-substrate interactions and catalytic activity in oxidase and hydrolase-like reactions. Of particular interest is the epoxidation of allylic alcohols and the catalytic cleavage of esters and amides.