Chemistry Department, Johns Hopkins University, Baltimore, MD, 21218, USA.
Chemistry Department, Stanford University, Stanford, CA, 94305, USA.
Angew Chem Int Ed Engl. 2021 Mar 8;60(11):5907-5912. doi: 10.1002/anie.202013791. Epub 2021 Feb 3.
A new end-on low-spin ferric heme peroxide, [(P )Fe -(O )] (P -P), and subsequently formed hydroperoxide species, [(P )Fe -(OOH)] (P -HP) are generated utilizing the iron-porphyrinate P with its tethered axial base imidazolyl group. Measured thermodynamic parameters, the ferric heme superoxide [(P )Fe -(O )] (P -S) reduction potential (E°') and the P -HP pK value, lead to the finding of the OO-H bond-dissociation free energy (BDFE) of P -HP as 69.5 kcal mol using a thermodynamic square scheme and Bordwell relationship. The results are validated by the observed oxidizing ability of P -S via hydrogen-atom transfer (HAT) compared to that of the F superoxide complex, [(F )Fe -(O )] (S) (F =tetrakis(2,6-difluorophenyl)porphyrinate, without an internally appended axial base imidazolyl), as determined from reactivity comparison of superoxide complexes P -S and S with the hydroxylamine (O-H) substrates TEMPO-H and ABNO-H.
利用带有桥连轴向咪唑基团的铁卟啉 P，生成了新型端位低自旋六配位铁血红素过氧化物 [(P )Fe -(O )] (P -P) 和随后形成的过氧物种 [(P )Fe -(OOH)] (P -HP)。测量热力学参数，铁血红素过氧化物 [(P )Fe -(O )] (P -S) 的还原电位 (E°') 和 P -HP 的 pK 值，通过热力学正方形方案和 Bordwell 关系，得到 P -HP 的 OO-H 键离解自由能 (BDFE) 为 69.5 kcal/mol。通过与没有内部桥连轴向咪唑基团的 F 超氧化物配合物 [(F )Fe -(O )] (S)（F = 四(2,6-二氟苯基)卟啉）相比，通过 HAT 进行的氢原子转移 (HAT) 观察到 P -S 的氧化能力，验证了结果，这是通过超氧化物配合物 P -S 和 S 与羟胺 (O-H) 底物 TEMPO-H 和 ABNO-H 的反应性比较来确定的。
