Cobalt complexes dioxygen carriers

Cyclodene Complexes Relationships between Macrocyclic Ring Size, Lacunar Cavity Shape, and Dioxygen Affinity of the Cobalt-Cyclidene Dioxygen Carriers. 

REVERSIBLE COBALT(II) AND IRON(II) DIOXYGEN CARRIERS OF TOTALLY SYNTHETIC LACUNAR CYCLIDENE COMPLEXES ... 

Busch, D.H. Alcock, N.W. Iron and cobalt "lacunar" complexes as dioxygen carriers. Chem. Rev. 1994, 94. 585-623. 

Cobalt complexes with cyclic and acyclic polyamines as hgands in aqueous solutions as dioxygen carriers 12CCR316. 

Various cobalt (II) complexes, usually referred to as synthetic dioxygen carriers, are known to interact reversibly with dioxygen under ambient conditions, affording predominantly dioxygen complexes of different types. 

The autoxidation of dioxygen carriers may involve both metal-centered oxidation to Co and ligand oxidation, leading to ligand destmction. Typical Mgand oxidations involve oxidative dehydrogenation of -CHyNH-to imine bonds as in the case of cobalt (II) complexes of Pydien and y-carbon to carbonyl group oxidations in macrocyclic p-diimine chelates ... 

It has long been known that, when bound to cobalt(II), the pyridine-based chelate ligands 2,2 -bipyridine (bipy), 1,10-phenanthroline (phen), and 2,2 6, 2"-terpyridine (terpy) form complexes that react with dioxygen in aqueous solution (32-34). The mixed-ligand complexes [Co(terpy)(bipy)]2+ and [Co(terpy)(phen)]2+ can act as oxygen carriers in aqueous solutions at pH values as low as 3.0 (34b), and the superoxo species thus formed are apparently dinuclear. In addition, the dinuclear bipyridine complex [(bipy)2Coin(/ 2-0 )(/ 2-02 )CoIn(bipy)2 ]3+ has been shown to catalyze the oxidation of 2,6-di-ter -butylphenol to the feri-butyl-substituted diphenoquinone and quinone (35). 

McLendon G, MarteU AE (1976) Inorganic oxygen carriers as models for biological systems. Coord Chem Rev 19 1-8 McLendon G, Harris W, MarteU AE (1976) Dioxygen compl-exation by cobalt amino acid and peptide complexes. 1. Stoichiometry and equilibria. J Am Chem Soc 98 8379-8386... 

The syntheses of two complexes are described here the cobalt(II) lacunar cyclidene complex in which R =—(CH2)e— and = R = —CH3, and the iron(II) complex in which R =m-xylylene, R = —CH2C6H5, and R = —CgHs- The former is the most studied example of a lacunar cyclidene oxygen carrier, and the latter represents the first nonporphyrin iron complex capable of forming a stable dioxygen adduct at room temperature. 

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