Energy Transfer between Singlet (~1△g) and Triplet (~3∑_g~-) Molecular Oxygen in Aqueous Solution

摘要

Singlet oxygen in its first excited state, denoted as O_2 (~1△_g), can be produced by type II photosensitization reaction1 and chemically in the reaction of hydrogen peroxide with hypochlorite or peroxynitrite, in the self-reaction of peroxyl radicals by the Russell mechanism, and through decomposition of dioxetanes and endoperoxides. O_2 (~1△_g) is also generated enzymatically by peroxidases and oxidases.7 The presence of a pair of electrons with opposite spins in the highest occupied molecular orbital confers dienophile features to O_2 (~1△_g) that explain its substantial reactivity toward electron-rich organic molecules, particularly with those exhibiting conjugated double bonds.