Design, synthesis and activity of catalysts inspired by manganese based enzymes

SIGNORELLA, S.

Bento Gonçalves

Workshop; Workshop on Synthetic Inorganic Chemistry (WSIC); 2011

Universidad de Santa María

The major biological roles of Mn are related to oxygen metabolism; i.e. making oxygen in photosystem II and as the cofactor for antioxidant defense enzymes. The number and type of ligands, the charges of surrounding protein residues, more than one manganese ion clustered together, are among the factors that introduce a way of tuning the redox potential of the metal center to face redox challenges that arise as a consequence of aerobic lifestyles. The redox function of Mn is reflected in the active site of specialized enzyme systems, such as catalases, superoxide dismutases and the oxygen evolving center of photosystem II. Biomimetic compounds provide a unique way to rationalize the catalytic mechanisms in these enzymes and dictate the critical features for obtaining efficient catalysts for ROS scavenging and water oxidation. We have evaluated the activity of several families of manganese complexes with a number of polydentate ligands with N/O ratios and different donor site gaps, to catalyze ROS scavenging and water oxidation, and correlated their catalytic acitivity with the geometrical motif of the metal center and electronic properties modulated by the ligands. Our results provide some clues that contribute to delineate more effective mimics that could find applications as therapeutic agents against oxidative stress and as catalysts of water oxidation in artificial photosynthesis.