Redox Behavior and Kinetics of Hydroxo Ligand Exchange on Iron Tetraphenylporphyrin. Comparison with Chloro Exchange and Consequences for its Role in Self-Modulation of Molecular Catalysis of Electrochemical Reactions
Résumé
Thermodynamics and kinetics of hydroxide ion binding to iron tetraphenylporphyrin (TPPFe) at different redox states is investigated by electrochemistry and UV-vis spectroscopy. The reduction of TPPFe drastically decreases the binding affinity of hydroxide ions. An activation-driving force correlation is revealed showing that the strongest the binding affinity, the largest the association rate constant and vice-versa. Comparison with chloride ions shows that hydroxide ions are stronger ligands for iron tetraphenylporphyrin. However, kinetic data indicate that coordination and de-coordination of chloride ions is intrinsically faster than coordination and de-coordination of hydroxide ions. Finally, the consequence of hydroxide ion binding dynamics when TPPFe is used as a molecular catalyst for electrochemical reactions liberating hydroxides is discussed in the framework of self-modulation of catalytic processes.
Domaines
ChimieOrigine | Fichiers produits par l'(les) auteur(s) |
---|---|
Licence |