1. + current, cathodic ic
+ potential, V
- potential, V
- current, anodic ia

2. + current, cathodic ic
Reduction
+ potential, V
- potential, V
Oxidation
- current, anodic ia

3. + current, cathodic ic When no electroactive species is present,
no current flows,
no ic nor ia
This is what background
electrolyte should look like.
+ V
- V
+1.0 V
-1.0 V
- current, anodic ia

4. Initially no current flows
+ current, cathodic ic
Starting at a + V,
Initially no current flows
+ V
- V
+1.0 V
-1.0 V
- current, anodic ia

5. is present ic will increase + current, cathodic ic
If a reducible species
is present ic will increase
+ current, cathodic ic
+ V
- V
+1.0 V
-1.0 V
- current, anodic ia

6. And continue to increase + current, cathodic ic
+ V
- V
+1.0 V
-1.0 V
- current, anodic ia

7. Until all of the species is reduced. ic has reached a maximum.
+ current, cathodic ic
+ V
- V
+1.0 V
-1.0 V
- current, anodic ia

8. Then ic decreases until… + current, cathodic ic
+ V
- V
+1.0 V
-1.0 V
- current, anodic ia

9. background current level. + current, cathodic ic
It again reaches the
background current level.
+ current, cathodic ic
+ V
- V
+1.0 V
-1.0 V
- current, anodic ia

10. Now the potential is reversed + current, cathodic ic
- current, anodic ia

11. And as V is more positive, The reduced species can be Re-oxidixed
+ current, cathodic ic
+ V
- V
+1.0 V
-1.0 V
- current, anodic ia

12. So ia decreases to a maximum + current, cathodic ic
+ V
- V
+1.0 V
-1.0 V
- current, anodic ia

13. Where all has been oxidized, + current, cathodic ic
+ V
- V
+1.0 V
-1.0 V
- current, anodic ia

14. Then ia decreases, back to the background level. + current, cathodic
- current, anodic ia

15. Important features: + current, cathodic ic +1.0 V -1.0 VEc
+ V
- V
+1.0 V
-1.0 V
- current, anodic ia Ea

16. + current, cathodic ic E1/2 is ~ EoRed +1.0 V -1.0 V - current, anodicEc
E1/2 is ~ EoRed
E1/2
+ V
- V
+1.0 V
-1.0 V
- current, anodic ia Ea

17. + current, cathodic ic Using an Fe(3+) heme, Fe is electroactive,
(and also the heme!) …
All Fe(3+)
+ V
- V
+1.0 V
-1.0 V
- current, anodic ia

18. + current, cathodic ic +1.0 V -1.0 V - current, anodic ia
A little Fe(2+) formed
+ V
- V
+1.0 V
-1.0 V
- current, anodic ia

19. + current, cathodic ic +1.0 V -1.0 V - current, anodic ia
more Fe(2+) formed
+ V
- V
+1.0 V
-1.0 V
- current, anodic ia

20. + current, cathodic ic +1.0 V -1.0 V - current, anodic ia
Largest cathodic current,
Max rate of Fe(2+) formed
+ V
- V
+1.0 V
-1.0 V
- current, anodic ia

21. + current, cathodic ic +1.0 V -1.0 V - current, anodic ia
Little Fe(3+) left;
Less Fe(2+) forms;
Decrease in ic
+ V
- V
+1.0 V
-1.0 V
- current, anodic ia

22. + current, cathodic ic +1.0 V -1.0 V - current, anodic ia
all Fe(2+) now
+ V
- V
+1.0 V
-1.0 V
- current, anodic ia

23. + current, cathodic ic
+ V
- V
+1.0 V
-1.0 V
- current, anodic ia

24. + current, cathodic ic +1.0 V -1.0 V - current, anodic ia
A little Fe(2+) is
re-oxidized to
Fe(3+)
+1.0 V
-1.0 V
- current, anodic ia

25. + current, cathodic ic
+ V
- V
+1.0 V
-1.0 V
- current, anodic ia

26. + current, cathodic ic +1.0 V -1.0 V - current, anodic ia
Nearly all Fe(2+)
has been oxized
- current, anodic ia

27. + current, cathodic ic +1.0 V -1.0 V - current, anodic ia
All back to Fe(3+).
Cycle could be run
again, many times.
- current, anodic ia

28. Important features: + current, cathodic ic +1.0 V -1.0 VEc
+ V
- V
+1.0 V
-1.0 V
- current, anodic ia Ea

29. E1/2 for Fe(3+/2+) reduction
+ current, cathodic ic Ec
E1/2 for Fe(3+/2+) reduction
E1/2
+ V
- V
+1.0 V
-1.0 V
- current, anodic ia Ea

30. the black box Working Electrode:
Where the redox reaction action occurs

31. the black box Working Electrode:
Where the redox reaction action occurs
Reference Electrode:
Defines “0” potential for the cell.
We use Ag/AgCl

32. the black box Working Electrode:
Where the redox reaction action occurs
Auxilliary Electrode:
Needed to complete circuit.
We use a Pt wire
Reference Electrode:

33. At start of CV experiment…
the
black
box
Working Electrode:
Where the redox reaction action occurs
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
At start of CV experiment…

34. Moving up the cathodic current peak…
black
box
Working Electrode:
Where the redox reaction action occurs
Fe(2+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Moving up the cathodic current peak…

35. Still moving up the cathodic current peak…
black
box
Working Electrode:
Where the redox reaction action occurs
Fe(2+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(2+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Still moving up the cathodic current peak…

36. After the maximum cathodic current peak…
black
box
Working Electrode:
Where the redox reaction action occurs
Fe(2+)
Fe(2+)
Fe(3+)
Fe(3+)
Fe(2+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
After the maximum cathodic current peak…

37. Moving down the anodic current peak…
black
box
Working Electrode:
Where the redox reaction action occurs
Fe(2+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(2+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Moving down the anodic current peak…

38. Sill moving down the anodic current peak…
black
box
Working Electrode:
Where the redox reaction action occurs
Fe(2+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Sill moving down the anodic current peak…

39. At end of CV experiment…
the
black
box
Working Electrode:
Where the redox reaction action occurs
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
Fe(3+)
At end of CV experiment…

40. In your CV scans of
Fe(porphyrin)Cl, you will see:
+ ic
- V
+ V
Interpretation????
- ia

41. How is the range of Heme Potentials
in Respiration adjusted?

42. The Question asked:
Can changing Heme substituents vary Fe(3+/2+) redcution potentials?