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- Title
Ferric Heme Superoxide Reductive Transformations to Ferric Heme (Hydro)Peroxide Species: Spectroscopic Characterization and Thermodynamic Implications for H‐Atom Transfer (HAT).
- Authors
Kim, Hyun; Rogler, Patrick J.; Sharma, Savita K.; Schaefer, Andrew W.; Solomon, Edward I.; Karlin, Kenneth D.
- Abstract
A new end‐on low‐spin ferric heme peroxide, [(PIm)FeIII−(O22−)]− (PIm‐P), and subsequently formed hydroperoxide species, [(PIm)FeIII−(OOH)] (PIm‐HP) are generated utilizing the iron‐porphyrinate PIm with its tethered axial base imidazolyl group. Measured thermodynamic parameters, the ferric heme superoxide [(PIm)FeIII−(O2⋅−)] (PIm‐S) reduction potential (E°′) and the PIm‐HP pKa value, lead to the finding of the OO−H bond‐dissociation free energy (BDFE) of PIm‐HP as 69.5 kcal mol−1 using a thermodynamic square scheme and Bordwell relationship. The results are validated by the observed oxidizing ability of PIm‐S via hydrogen‐atom transfer (HAT) compared to that of the F8 superoxide complex, [(F8)FeIII−(O2.−)] (S) (F8=tetrakis(2,6‐difluorophenyl)porphyrinate, without an internally appended axial base imidazolyl), as determined from reactivity comparison of superoxide complexes PIm‐S and S with the hydroxylamine (O‐H) substrates TEMPO‐H and ABNO‐H.
- Subjects
HEME; HYDROPEROXIDES; PEROXIDES; SUPEROXIDES; REDUCTION potential; SPECIES
- Publication
Angewandte Chemie, 2021, Vol 133, Issue 11, p5972
- ISSN
0044-8249
- Publication type
Article
- DOI
10.1002/ange.202013791