Chemical Insights into the Antioxidant Mechanisms of Alkylseleno and Alkyltelluro Phenols: Periodic Relatives Behaving Differently

The possible antioxidant reaction mechanisms of recently synthesized and tested alkylseleno (telluro) phenols have been explored using density functional theory by considering two solvents physiologically relevant, water and pentylethanoate (PE). In addition, the possible pathway for the antioxidant regeneration with ascorbic acid has been investigated. Results show that selenium and tellurium systems follow different chemical behaviors. In particular, the alkylseleno phenol (ebselenol) antioxidant activity is justified through a sequential proton loss-electron-transfer mechanism in water media, whereas in PE the hydrogen-atom transfer process is favored. In the case of the tellurium derivative, the oxygen-transfer mechanism represents the preferential one. Furthermore, electronic properties have been analyzed to rationalize the different reactivity of the selenium- and tellurium-containing systems. To confirm the results, smaller but similar systems were also investigated. The calculated data support the different mechanism (Se vs. Te) proposals.