Biomimetic manganese oxide

Selective Conversion of Hydrocarbons with H202 Using Biomimetic Non-heme Iron and Manganese Oxidation Catalysts... 

SELECTIVE CONVERSION OF HYDROCARBONS WITH H2O2 USING BIOMIMETIC NON-HEME IRON AND MANGANESE OXIDATION CATALYSTS... 

A simplihed model has been developed to investigate the simplest complete OER reaction cycle. It is inspired by the biomimetic manganese dimers used for studying the water oxidation reaction in biological systems. The interest in these systems is twofold since they offer candidates for possible future water oxidation catalysts [61]. 

Oaki, Y. and Imai, H. (2007) Biomimetic morphological design for manganese oxide and cobalt hydroxide nanoflakes with a mosaic interior. Journal of Materials Chemistry, 17, 315-21. 

Najafpour MM, Ehrenberg T, Wiechen M, Kurz P. Calcium manganese(III) oxides (CaMn204 x H20) as biomimetic oxygen-evolving catalysts. Angew Chem Int Ed. 2010 49(12) 2233-7. 

Manganese dioxide as an oxidant has been nsed for biomimetic syntheses of benzyliso-qninoline alkaloids and other natnral prodncts, bnt the yields are low . ... 

One-electron withdrawing inorganic reagents have been used to perform biomimetic syntheses of phenolic phenethylisoquinoline alkaloids. In order to obtain androcymbine compounds of type 85, the diphenolic isoquinoline 82a was subjected to phenol oxidation with manganese dioxide. The homoaporphine 83a coupled at the ortho-ortho position to the hydroxy group was the only product formed under these reaction... 

In pursuit of biomimetic catalysts, metaUoporphyrins have been extensively studied in attempts to mimic the active site of cytochrome P450, which is an enzyme that catalyzes oxidation reactions in organisms. In recent decades, catalysis of alkene epoxidation with metaUoporphyrins has received considerable attention. It has been found that iron [1-3], manganese [4,5], chromium [6], and cobalt porphyrins can be used as model compounds for the active site of cytochrome P450, and oxidants such as iodosylbenzene, sodium hypochlorite [7,8], hydrogen peroxide [9], and peracetic acid [10] have been shown to work for these systems at ambient temperature and pressure. While researchers have learned a great deal about these catalysts, several practical issues limit their applicability, especially deactivation. 

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]. 

The present review has outlined the efforts to develop biomimetic non-heme iron and manganese catalysts for alkane hydroxylation, olefin epoxidation, and cis-dihydroxylation reactions. However, the examples reviewed here are mostly presented as reported in the literature, since the various reaction conditions involved in the catalytic oxidations hamper a direct comparison and critical evaluation of the data. The survey has not only illustrated a rich variety of iron and manganese complexes that lead to the successful structural modeling of important non-heme iron and manganese enzymes, but also significant features of the oxidation reactions catalyzed by these complexes in combination with dihydrogen peroxide. 

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