Dioxygen Ligands

Coordination substances called dioxygen complexes have O 2 as a ligand. Oxygen-transporting proteins including myoglobin, haemoglobin, hemerythrin, and hemocyanin serve as inspiration for the research of these substances. Many of the complexes formed by transition metals and O 2 are reversible. About 20% by volume of the earth's atmosphere is made up of dioxygen. With two unpaired electrons, one in each of the doubly degenerate *HOMOs, molecular oxygen is a ground-state triplet. Formally, molecular oxygen possesses a double bond and is a potent oxidant in terms of thermodynamics. However, because of spin conservation, the interaction of O2 with ground-state singlet molecules is kinetically unfavourable and necessitates the reaction with additional ground-state radicals, such as flavins, pterins, or metal ions.