Density functional theory study of transitional metal macrocyclic complexes' dioxygen-binding abilities and their catalytic activities toward oxygen reduction reaction

In this paper, density functional theory method is applied to study the dioxygen-binding abilities of transition metal macrocyclic complexes and their electrocatalytic activities toward oxygen reduction reaction. Both end-on and side-on binding modes are examined. Electronic properties, such as ionization potential and Mulliken charge, are evaluated. The effects of central metal, ligand, and substituents on catalyst's dioxygen-binding ability and catalytic activity are investigated. The binding nature of dioxygen adduct is analyzed based on structure property. The general activity trend observed for phthalocyanines and porphyrins is rationalized with the calculated properties. It is illustrated that the catalyst's oxygen reduction activity is related to its ionization potential and dioxygen-binding ability. Cobalt porphyrin derivatives have high ionization potentials, which make them better catalysts than the corresponding iron derivatives, whereas for phthalocyanine systems, iron derivatives have large ionization potential and better dioxygen-binding ability, which make them good catalysts.