The Role of Singlet and Triplet Dioxygen Molecules in the EPR and 1H NMR Spectrum Line Broadening

In the Mo^(VI)/H₂O₂/H₂O system, the relaxation time (T ₁) of protons in a water molecule and in a CH₃ group decreases 10 to 30 times under conditions of dismutation of H₂O₂ with the formation of ¹O₂(¹_g). It is experimentally found that the overequilibrium concentration of triplet dioxygen cannot be the reason behind a decrease in T ₁ in the ¹H NMR spectra. Neither can it explain the anomalous line broadening in ESR spectra under conditions of ¹O₂(¹_g) formation in the systems V^(V)/H₂O₂/AcOH and Mo^(VI)/H₂O₂/H₂O. Ab initio calculations showed that it is principle possible that the ³O₄(³·^- _g-¹_g) molecule exists in a snake-like form and is formed by the reaction between ³O₂(³·^- _g) and ¹O₂(¹_g), which is the product of H₂O₂ decomposition in the systems V^(V)/H₂O₂/AcOH and Mo^(IV)/H₂O₂/H₂O. The interaction of ¹O₂ with the ·OOH radical is exothermic (Q = 2.30 kcal/mol) and leads to the formation of ·OOOOH. It is assumed that the paramagnetic species of type ·OOOOH or ³O₄(³ A ₁) that is formed in the reaction might be responsible for the spectral effects observed.