Figure 2.

(Left) after excluding H₂O₂ (red) from Scheme 2g, the remaining di-cation species is posed π-π to a superoxide radical, 3.50 Å. Its geometry optimization shown here enables the superoxide to be incorporated into the polyphenol system, with centroid-centroid separation, 2.766 Å, and keeping H₂O₂ π-π bound to the ring, 3.024 Å. (Right) the cation shown on the left is van der Waals posed (2.60 Å) by an additional superoxide nearing H(hydroxyl) in position 5. This σ approaching superoxide evolves toward formation of O₂ (O–O bond = 1.271 Å), detached from the remaining species (3.106 Å), which is a galangin complex comprising π-π bound H₂O₂ and O₂.