title: Concerted proton-electron transfer in electrocatalytic O2 reduction by iron porphyrin complexes: axial ligands tuning H/D isotope effect.
abstract: The electrochemical O2 reduction by thiolate- and imidazole-bound iron porphyrin complexes and H/D isotope effects on 4e(-) (determined by rotating disc electrochemistry) and 2e(-) (determined by rotating ring disc electrochemistry) O2 reduction rates are investigated. The results indicate that a thiolate axial ligand shows an H/D isotope effect greater than 18 and 47 for the 4e(-) and 2e(-) O2 reductions, respectively. Alternatively, an imidazole axial ligand results in H/D isotope effects of 1.04 and 4.7 for the 4e(-) and 2e(-) O2 reduction, respectively. The catalytic O2 reduction mechanism is investigated in situ with resonance Raman coupled with rotating disc electrochemistry. The data indicate that the rate-determining step changes from O-O bond heterolysis of Fe(III)-OOH species for a thiolate axial ligand to an O-O bond heterolysis of an Fe(II)-OOH for an imidazole axial ligand.
authors.affiliation: Department of Inorganic Chemistry, Indian Association for the Cultivation of Science , Kolkata 700032, India.
authors.forename: Sudipta
authors.initials: S
authors.lastname: Chatterjee
authors.forename: Kushal
authors.initials: K
authors.lastname: Sengupta
authors.forename: Subhra
authors.initials: S
authors.lastname: Samanta
authors.forename: Pradip Kumar
authors.initials: PK
authors.lastname: Das
authors.forename: Abhishek
authors.initials: A
authors.lastname: Dey
mesh_terms: D002384:Catalysis; D041961:Deuterium Exchange Measurement; D055664:Electrochemical Techniques; D004583:Electrons; D007501:Iron / Q000737:chemistry*; D008024:Ligands; D008665:Metalloporphyrins / Q000737:chemistry*; D015394:Molecular Structure; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*; D011522:Protons
chemical_list: D008024:Ligands; D008665:Metalloporphyrins; D011522:Protons; D007501:Iron; D010100:Oxygen