The Role of Chalcogen in the ROS Scavenging Mechanism of Model Phenyl Compounds

Phenolic compounds are important antioxidants with great ROS scavenging potential and the presence of the hydroxyl groups is fundamental for this chemical activity. Therefore, changing the chalcogen atom (oxygen) with any of its siblings of group 16 (sulfur, selenium and tellurium) may affect the reactivity of these compounds. In this work, the ROS scavenging activity and mechanism of phenyl chalcogenols was evaluated in silico, unravelling better performance with heavier chalcogens, both thermodynamically and kinetically. Furthermore, a scavenging mechanism switch is reported, moving from Concerted Proton Electron Transfer (CPET) in phenols to Hydrogen Atom Transfer (HAT) in the other phenyl chalcogenols. Both kinetic trends and mechanistic features are rationalized in the framework of Activation Strain Analysis (ASA). Lastly, the role of aromaticity is evidenced by analyzing the differences between the phenol/phenoxyl and methanol/methoxyl self-exchange reactions, as well as between the corresponding processes with the other chalcogens.