Free Forms of Activated Dioxygen Generated by Metals

Free Forms of Activated Dioxygen Generated by Metals 

The oxidation of oxygen by iron or copper enzymes, for example, to generate O2 is highly unlikely since oxygen is a poor electron donor as its high ionization potential (+12.1 e. v.) indicates (65). In fact, only highly electronegative metal complexes such as [PtFs] can accomplish oxidation (66). 

Electronic excitation of oxygen by metallo-enzymes poses three special problems. The first concerns the provision of the 23 kcal/mol necessary for excitation, the second concerns the avoidance of undesired quenching of singlet oxygen before it encounters the substrate and the third concerns the recovery of excess energy from vibrationally excited products (77). 

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