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

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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.