Dioxygen reactivity, biomimetic

Keywords Biomimetic dioxygen reactivity Copper Coupling reactions ... 

Karlin, K. D. Zuberbuhler, A. D. Formation, structure, and reactivity of copper dioxygen complexes, Bioinorganic Catalysis , 2nd edn. (Revised and Expanded) Eds. Reedijk, J. Bouwman, E. Marcel Dekker New York, 1999, pp. 469-534. Fukuzumi, S. Imahori, H. Biomimetic electron-transfer chemistry of porphyrins and metalloporphyrins, Electron Transfer in Chemistry , Vol. 2 Ed. Balzani, V. Wiley-VCH Verlag GmbH Weinheim, 2001, pp. 927-975. 

Copper-dioxygen complexes are necessary intermediates in the biomimetic oxidations performed by type 3 Cu models. Several structural motifs for synthetic Cu 02 complexes exist and the main types are shown in Scheme 4. Their mechanism of formation, structural characteristics, spectroscopic and thermodynamic properties, and reactivity have been recently thoroughly reviewed (62,63). In general, the reaction between a Cu(I) complex and dioxygen initially forms a 1 1 Cu/02 adduct that, in the absence of steri-cally hindered ligands, rapidly evolves to the thermodynamically more stable 2 1 Cu/02 adduct. According to the usual formalism, these processes can be described by the following equilibria ... 

The reoxidation step appears to involve a very reactive copper-dioxygen intermediate, which recentfy has been studied spectroscopically and kmeticaUy for certain biomimetic systems. 

Biomimetic copper-dioxygen chemistry has advanced considerably since the first structurally-characterized copper-dioxgygen adduct. However, it has been difficult to simulate the room-temperature stability of hemocyanin in these model complexes due to the fact that unlike the enzyme active sites, these models usually do not possess protective environments which can help stabilize potentially reactive copper-dioxygen species. Recently, two room-temperature stable copper-dioxygen complexes have been synthesized which come closer to the goal of mimicking the dioxygen carrier hemocyanin. 

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