Manganese biomimetic synthesis

Biomimetic oxidation catalysis has largely focused on complexes with planar tetradentate ligands such as manganese or iron porphyrins and related macrocyclic trans-chelates[5]. There is considerable interest in the synthesis of multinuclear metal complexes since these molecules might be useful as building block for magnetic molecular materials[6] and model compounds for understanding the properties of metalloproteins[7]. 

Figure 9.9 Synthesis of DHP using the Zutropf method with peroxidase and hydrogen peroxide or manganese(III)-acetate in acetic acid with or without the presence of water. The biomimetic DHPs were fully acetylated and the high molecular weight fraction obtained after chromatography on polystyrene gel [46].

In order to generate more structurally relevant biomimetics for dinuclear metallohydrolases much effort has been devoted to the synthesis of asymmetric ligands. These ligands are considered to be more suitable models for the asymmetric coordination environment found in enzymatic systems. Nordlander et al. proposed that asymmetric complexes are not only more appropriate functional models for the active site of phosphoesterase enzymes, but also that they exhibit enhanced catalytic rates compared with their symmetric counterparts [1-3]. A selection of ligands used to generate purple acid phosphatase [1, 4, 5, 6-10], phosphoesterase [11], urease [12, 13], catechol oxidase [14] and manganese catalase biomimetics [15, 16] is displayed in Fig. 7.1. 

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