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

[Cu(NH 3 ) 4 ] 2+ (aq) [Cu(NH 3 ) 2 ] + (aq) Cu [Cu(OH 2 ) 5 ] 2+ (aq) [Cu(OH 2 ) 2 ] + (aq) Cu

phenanthroline 4,7-dimethylphenanthroline 2,9-dimethylphenanthroline Now we react the Cu(II) with a series of phenanthroline-based ligands E o for [CuL 2 ] 2+ /[CuL 2 ] + (Volts) 2,9-di-Mephen0.823 V 4,7-di-Mephen0.256 V phen0.322 V

phenanthroline 4,7-dimethylphenanthroline 2,9-dimethylphenanthroline Now we react the Cu(II) with a series of phenanthroline-based ligands E o for [CuL 2 ] 2+ /[CuL 2 ] + (Volts) 2,9-di-Mephen0.823 V 4,7-di-Mephen0.256 V phen0.322 V

Ligand’s Influence on Redox Potential

Influence of coordinated atoms on redox potential

THERE’S METALS IN THERE!!!!!!!!!!

Follows Krebs Cycle Results in oxidative phosphorylation Electron transport chainYes! Every Step uses a metalloenzyme

Redox Potential for Electron Transport Proteins

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

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

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

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

Reduction Potential Difference =  Eº   Eº = 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.

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

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

Standard Reduction Potential Oxidant Reductant n Eº, v NAD + NADH acetaldehyde ethanol pyruvate lactate oxaloacetate malate /2 O 2 +2H + H 2 O

Redox Function Thermodynamics = redox potential: (  G = -nFE 0 ) 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 Z eff - all orbital energy levels (stronger ligand donation  lower Z eff  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)

-- 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).

Superoxide Dismutase [CuZnSOD]

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?