An Introduction to Electrochemistry in Inorganic Chemistry

1. An Introduction to Electrochemistry in Inorganic Chemistry Or Quack…. Quack….I see a duck

6. [Cu(NH3)4]2+ (aq) [Cu(NH3)2]+ (aq) Cu [Cu(OH2)5]2+ (aq) [Cu(OH2)2]+ (aq) Cu

7. Now we react the Cu(II) with a series of phenanthroline-based ligands phenanthroline 4,7-dimethylphenanthroline 2,9-dimethylphenanthroline WHY???

10. Now we react the Cu(II) with a series of phenanthroline-based ligands phenanthroline 4,7-dimethylphenanthroline 2,9-dimethylphenanthroline

12. Ligand’s Influence on Redox Potential

13. Influence of coordinated atoms on redox potential

16. Now Let's Look a few biological systems WHY? Well do I really have to tell you? THERE’S METALS IN THERE!!!!!!!!!!

17. Electron transport chain Follows Krebs Cycle Results in oxidative phosphorylation Yes! Every Step uses a metalloenzyme

18. Redox Potential for Electron Transport Proteins

19. Rubredoxin (Rd) Oxidized rubredoxin (1IRO) from Clostridum pasterurianum at 1.1Å

20. [2Fe] Ferredoxin oxidized Spinach ferredoxin (1A70) from Spinacia oleracea at 1.7Å

21. [4Fe] Iron Proteins (1BLU) from Chromatim vinosum at 2.1Å (1IUA) from Thermochromatium tepidum at 0.8Å

25. So, the more negative the reduction potential is, the easier a reductant can reduce an oxidant and The more positive the reductive potential is, the easier an oxidant can oxidize a reductant The difference in reduction potential must be important

27. Reduction Potential Difference =DEº DEº = E°(acceptor) - E°(donor)  measured in volts.  The more positive the reduction potential difference is, the easier the redox reaction  Work can be derived from the transfer of electrons and the ETS can be used to synthesize ATP.

28.  The reduction potential can be related to free energy change by: Gº = -nFDEº where n = # electrons transferred = 1,2,3 F = 96.5 kJ/volt, called the Faraday constant

29. **************************************************************************************************************************************** Table of Standard Reduction Potentials --- Oxidant + e- reductant -- e.g., M&vH, 3rd ed., p. 527 Note: oxidants can oxidizeevery compound with less positive voltage -- (above it in Table) reductants can reduceevery compound with a less negative voltage -- (below it in Table) **********************************************************************

30. Standard Reduction Potential Oxidant Reductant n Eº, v NAD+ NADH 2 -0.32 acetaldehyde ethanol 2 -0.20 pyruvate lactate 2 -0.19 oxaloacetate malate 2 -0.17 1/2 O2+2H+ H2O 2 +0.82

31. Redox Function • Thermodynamics = redox potential: (DG = -nFE0) • ionization energy - electronic structure • a) HOMO/LUMO - redox active orbital energy • (stronger metal-ligand bonding  raises the orbital energy  • easier to oxidize  potential goes down) • b) metal Zeff - all orbital energy levels • (stronger ligand donation  lower Zeff raised d-orbitals ...) • c) electron relaxation - allow for orbital reorg. after redox • (creation of a hole upon oxidation  passive electrons shift •  larger thermodynamic driving force  potential goes down)

32. -- Electrons can move through a chain of donors and acceptors -- In the electron transport chain, electrons flow down a gradient. -- Electrons move from a carrier with low reduction potential (high tendency to donate electrons) toward carriers with higher reduction potential (high tendency to accept electrons).

33. Superoxide Dismutase[CuZnSOD]

34. 12Influenceson Redoxpotential:1)Metalcenter2)Electrostatic (ligand charge)3)σ/π-Donor strength of ligand (pKa)4)π-Acceptor strength of ligand5)Spin state6)Steric factors/ constraints (enthatic state)How can a protein chain generate these diverse redox potentials?