biostudies-literatureKim HNIGMS NIH HHS5907-5912https://www.ebi.ac.uk/biostudies/studies/S-EPMC7920932biostudies-literatureUnknown60(11)A new end-on low-spin ferric heme peroxide, [(P^Im )Fe^III -(O₂ ^2- )]^- (P^Im -P), and subsequently formed hydroperoxide species, [(P^Im )Fe^III -(OOH)] (P^Im -HP) are generated utilizing the iron-porphyrinate P^Im with its tethered axial base imidazolyl group. Measured thermodynamic parameters, the ferric heme superoxide [(P^Im )Fe^III -(O₂ ^⋅- )] (P^Im -S) reduction potential (E°') and the P^Im -HP pK_a value, lead to the finding of the OO-H bond-dissociation free energy (BDFE) of P^Im -HP as 69.5 kcal mol^-1 using a thermodynamic square scheme and Bordwell relationship. The results are validated bAngewandte Chemie (International ed. in English)Ferric Heme Superoxide Reductive Transformations to Ferric Heme (Hydro)Peroxide Species: Spectroscopic Characterization and Thermodynamic Implications for H-Atom Transfer (HAT).PMC7920932R01 GM040392R01 GM060353Kim HRogler PJSharma SKSolomon EISchaefer AWKarlin KDfalseFerric Heme Superoxide Reductive Transformations to Ferric Heme (Hydro)Peroxide Species: Spectroscopic Characterization and Thermodynamic Implications for H-Atom Transfer (HAT).A new end-on low-spin ferric heme peroxide, [(P^Im )Fe^III -(O₂ ^2- )]^- (P^Im -P), and subsequently formed hydroperoxide species, [(P^Im )Fe^III -(OOH)] (P^Im -HP) are generated utilizing the iron-porphyrinate P^Im with its tethered axial base imidazolyl group. Measured thermodynamic parameters, the ferric heme superoxide [(P^Im )Fe^III -(O₂ ^⋅- )] (P^Im -S) reduction potential (E°') and the P^Im -HP pK_a value, lead to the finding of the OO-H bond-dissociation free energy (BDFE) of P^Im -HP as 69.5 kcal mol^-1 using a thermodynamic square scheme and Bordwell relationship. The results are validated b2021-01-01T00:00:00Z2021 Mar2025-04-04T19:53:39.028Z2025-04-04T19:53:39.028ZS-EPMC79209323334845010.1002/anie.202013791