J. Am. Chem. Soc. 2007 , 129 , 4217 - 4228

1. Iron(III) Complex of a Crown Ether-Porphyrin Conjugate andReversible Binding of Superoxide to Its Iron(II) Form Katharina Dürr, Brendan P. Macpherson, Ralf Warratz, Frank Hampel, Felix Tuczek, Matthias Helmreich, Norbert Jux,*, and Ivana Ivanović-Burmazović,* J. Am. Chem. Soc. 2007, 129, 4217 - 4228 Speaker：鍾柏源

2. Hemoglobin Hemoglobin O2 Hemoglobin O2 維基百科，http://en.wikipedia.org/wiki/Hemoglobin

3. where M = Cu (n=1) ; Mn (n=2) ; Fe (n=2) ; Ni (n=2) Superoxide dismutase (SOD) The SOD-catalysed dismutation of Superoxide may be written with the following half-reactions : Journal of Inorganic Biochemistry,2002, 91, 349–355

4. Structures and formal oxidation states of iron-dioxygen complexes Chem. Rev. 1994, 94, 659-698

5. Fe(III)-peroxo-porphyrin complexes

6. Electron-withdrawing group No reaction The effect of electron-withdrawing groups on the stability J. Am. Chem. Soc. 1996, 118, 2008-2012

7. An interaction between the potassium ion and the coordinated peroxo ligand • Infrared spectra of the oxygen-oxygen • stretching region for • [K][Fe(OEP)O2] • [Me4N][Fe(OEP)O2] • => (A) is more stable than (B). J. Am. Chem. SOC.1988, 110, 1382-1388

8. Switching on the Nucleophilic Reactivity of a Ferric Porphyrin Peroxo Complex J. Am. Chem. SOC.1987, 109, 1425-1434 J. Am. Chem. Soc. 1998, 120, 2652-2653

9. Reflux 24hr Synthesis of Crown Ether-Porphyrin

10. X-ray crystal structure of [FeⅢ(Porph)Cl]

11. Synthesis • H2Porph • [FeⅢ(Porph)Cl] ：FeCl2 • [(FeⅢ(Porph))2O] ：2 M NaOH • K[FeⅢ(Porph)(CN)2] ：KCN • [FeⅢ(Porph)(DMSO)2]+：DMSO • [FeⅢ(Porph)OH] ：water or NaOH • [FeⅡ(Porph)] ：by chemical reduction • K[FeⅢ(Porph)(O22-)] ：KO2

12. Inorg. Chem. 2002, 41, 2761-2768 To study the influence of the potassium ion KCN β-pyrrolic protons： -3 and -5 ppm Bu4N+CN- β-pyrrolic protons： -8 to -10 ppm Authors interpret this to mean that the bulky Bu4N+ cation cannot be coordinated by the crown ether.

13. [FeⅢ(Porph)(DMSO)2]+ [FeⅢ(Porph)OH] [(FeⅢ(Porph))2O] 414 nm 420 nm 429 nm K[FeⅢ(Porph)(O22-)] [FeⅡ(Porph)(DMSO)2] 440 nm 430 nm UV/vis absorption spectra

14. After (λmax= 430 nm) Reduction by dithionite KO2 or dithionite Before (λmax= 420 nm) [FeⅢPorph(DMSO)2]+ = 5 x 10-6M KO2 = 5 x 10-5M At 25℃ in DMSO UV/vis spectra for the reaction of [FeⅢPorph(DMSO)2]+ and KO2

15. Before (λmax= 440 nm) After (λmax= 430 nm) K[FeⅢ(Porph)(O22-)] = 1 x 10-5M [HOTf] = 5 x 10-5M HOTf At 25℃ in DMSO Time-resolved spectra for the reaction of K[FeⅢ(Porph)(DMSO)(O22-)] and 5 x10-5 M HOTf

16. K[FeⅢ(Porph)(O22-)] + 0.1 M HOTf UV/vis spectra for the reaction of K[FeⅢPorph(DMSO)(O22-)] and 0.1 M HOTf

17. Conclusion 1

18. KOH Time-resolved spectra of the reaction of [FeⅢ(Porph)(DMSO)2]+ and KOH

19. KO2 Spectral changes during the reaction of [FeⅢ(Porph)(DMSO)OH] and KO2

20. 2,4,6-tri-(tert-butyl)phenol (TBPH) Before After mixing m-chloroperbenzoic acid (mCPBA) mCPBA = 10-3M TBPH = 10-1M [FeⅢ(Porph)Cl] = 1.3 x 10-5M At r.t in KCl-saturated DMSO/CH3CN Spectral changes upon mixing mCPBA with TBPH and [FeⅢ(Porph)Cl] TBPH forms an oxygen-centered radical, which results inan increase of absorbance at 380, 400, and 630 nm. J. Am. Chem. SOC. 1984, 106, 755-764

21. Conclusion 2

22. -1.06V -1.54V 0.225V -1.47V -0.983V 0.313V -1.23V -1.63V -1.56V -1.16V Cyclic voltammograms of [FeⅢ(Porph)Cl] and [ZnⅡ(Porph)] a) Redox couples for [FeⅢ(Porph)]+ under nitrogen b) Redox couples for [ZnⅡ(Porph)] under nitrogen

23. [FeⅢ(Porph)Cl] + KO2 Mössbauer Parameters of the Studied Complexes in Frozen DMSO at 80 K Mössbauer spectra of reduced 57Fe-enriched [FeⅢ(Porph)Cl] and K[FeⅢ(Porph)(O22-)] [FeⅢ(Porph)Cl]

24. Kinetics and Thermodynamics

25. [FeⅡ(Porph)] = 5 x 10-6M [KO2] = 5 x 10-4M KO2 Time-resolved spectra for the reaction between [FeⅡ(Porph)] and KO2 At 25℃ in DMSO

26. =>From the slope of the plot the second-order rate constant kon was determined to be 36500 500 M-1 s-1 ■:starting from the Fe(II) complex and using different mixing volume ratios ○:starting from the Fe(II) complex and preparing a new solution for each [O2] △:starting from the Fe(III) complex and preparing a new solution for each [O2-] Plots of kobs versus [O2-] for the second step of the reaction of 5 x 10-6 M complex and KO2 kobs / [O2-] = kon

27. Before (λmax= 440 nm) After (λmax= 430 nm) K[FeⅢ(Porph)(O22-)] = 1 x 10-5M [HOTf] = 5 x 10-5M First-order kobs= koff koff= 0.21 0.001 s-1 KO2- = kon / koff = (1.7 0.2) x 105 M-1 At 25℃ in DMSO Time-resolved spectra for the reaction of K[FeⅢ(Porph)(O22-)] and 5 x 10-5 M HOTf

28. [FeⅡ(Porph)(DMSO)2] = 5 x 10-6 M With electrolyte KO2- = (0.9 0.1) x 105 M-1 Without electrolyte KO2- = (1.4 0.1) x 104 M-1 Changes in absorbance upon addition of O2- to a solution of [FeⅡ(Porph)(DMSO)2]

29. 25℃ [FeⅢ(Porph)Cl] = 5X10-6 M [KO2] = 2.5X10-5 M Mixture of DMSO/CH3CN - 40℃ Time-resolved spectra for the reaction between [FeⅢ(Porph)Cl] and KO2

30. Eyring Equation [[FeⅢ(Porph)Cl]] = 5 x 10-6 M [KO2] = 1 mM kB = Boltzmann's constant [1.381·10-23 J · K-1] T = absolute temperature in degrees Kelvin (K) h = Plank constant [6.626·10-34 J · s] In the DMSO/CH3CN mixture (30% DMSO) Eyring plot for the second reaction step ΔH‡ = 61.2 ± 0.9 kJ mol-1 ΔS‡ = +48 ± 3 J K-1 mol-1

31. Kinetic and Thermodynamic Parameters for Binding of Superoxide to FeⅡ(Porph) at 25 °C (Second Reaction Step) Kinetic and Thermodynamic Parameters

32. => kobs= kon[O2-] + koff kon = k1k2/k-1 koff = k-2 Second-order First-order Dissociative mechanism

33. Conclusions • Authors have synthesized and characterized the new Fe(III)-porphyrin complex [FeⅢ(Porph)Cl], which carries a covalently bound aza-crown ether in close proximity to the iron center. • The second reaction step, binding of superoxide to the Fe(II) species and formation of the Fe(III)-peroxo complex, could be studied in detail. To our knowledge, this is the first time that superoxide concentration and temperature-dependent kinetic studies of reactions with superoxide. • Moreover, authors have observed for the first time that the superoxide anion can bind reversibly to a metal center.