THE ELECTRON-TRANSFER MECHANISM OF AUTOXIDATION FOR HEMOGLOBIN, MYOGLOBIN, AND THEIR IRON(II) CYCLIDENE MODELS

The rates of autoxidation of iron(II) cyclidenes have been studied as functions of dioxygen pressure and with variations in the size of the cavity within which the O2 molecules must reside in order to bind to the iron atom. As the cavity is opened up, first O2 and then solvent species can enter and bind to iron, and this is accompanied by changes in the algebraic form of the rate law for autoxidation. Analysis strongly suggests that the molecule of O2 that oxidizes the iron(II) is not bound, there by implicating an electron-transfer mechanism for the autoxidation process. The peculiar nature of the O2 dependences of myoglobin and hemoglobin autoxidations indicates that the same mechanism applies.