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Optical spectroscopy and nanosecond flash photolysis (Nd:YAG laser, 355 nm, pulse duration 5 ns, mean energy 5 mJ/pulse) were used to study the photochemistry of Fe(III)(C2O4)3(3-) complex in aqueous solutions. The main photochemical process was found to be intramolecular electron transfer from the ligand to Fe(III) ion with formation of a primary radical complex [(C2O4)2Fe(II)(C2O4(*))](3-). The yield of radical species (i.e., CO2(*-) and C2O4(*-)) was found to be less than 6% of Fe(III)(C2O4)3(3-) disappeared after flash. [(C2O4)2Fe(II)(C2O4(*))](3-) dissociates reversibly into oxalate ion and a secondary radical complex, [(C2O4)Fe(II)(C2O4(*))](-). The latter reacts with the initial complex and dissociates to Fe(II)(C2O4) and oxalate radical. In this framework, the absorption spectra and rate constants of the reactions of all intermediates were determined.

Transformed Gibbs free energy values of respiratory reactions are calculated to address the spontaneity, selectivity, control, and efficiency of oxidative phosphorylation. We present tangible explanations for ubiquinone’s role mitochondria, HCN > H2S order of cellular toxicity in aerobes and why oxygen inhibits anaerobes. Our data/arguments highlight the significance of proton deficiency in NADH/mitochondria and link the ‘oxygen → ROS (reactive oxygen species) → water’ metabolic pathway to the macroscopic physiologies of ATP-synthesis, trans-membrane potential, thermogenesis, and homeostasis. This ‘murburn perspective’ affords a probabilistically and thermodynamically viable precept for the origin and evolution of the ‘working logic’ of oxygen-centric life.

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