Energetics of the Interaction of Molecular Oxygen with Organic Molecules

The interaction of molecular oxygen with electronically excited organic molecules (M) has been examined theoretically and expressions for energies of the states of the [M···O2] complex have been derived. The results indicate that in [M···O2] complexes where the triplet state of the organic molecule, 3M, and the charge-transfer state of the complex are close in energy, (i) the O2 induced S→T absorption bands may be diffuse and red shifted relative to the positions of unperturbed bands; (ii) the quenching of triplet states by O2 will invariably be diffusion controlled; (iii) the [3M···3O2] complex has a significant binding energy (>300 cm−1); and (iv) complexes between a ground-state molecule and electronically excited oxygen molecules (either 1Σg+ or 1Δg) are dissociative.