Induction of Enzyme-like Peroxidase Activity in an Iron Porphyrin Complex Using Second Sphere Interactions

Emulating enzymatic reactivity using small molecules has been a long-time challenging pursuit of the scientific community. Peroxidases, ubiquitous heme enzymes that are involved in hormone synthesis and the immune system, have been a prime target of such efforts due to their tremendous potential in the chemical industry as well as in wastewater treatment. Here it is demonstrated that inclusion of a second sphere guanidine moiety in an iron porphyrin not only makes this small molecule a veritable peroxidase catalyst but also offers an auxiliary binding site for organic substrates, facilitating their rapid oxidation with a green oxidant like H₂O₂. This small molecule analogue exhibits a "ping-pong" mechanism and Michaelis-Menten type kinetics, which is generally typical of metallo-enzymes and follows a mechanism of the natural enzyme in its entirety, including the formation of compound I as the primary oxidant.