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OK, so you’ve made the Ru complexes.
Now, how are you going to determine what it does with DNA?
Will your complex bind DNA, like this?
Will the other complexes also bind DNA?
Will the other complexes cleave DNA?
Will your complex cleave (damage) DNA?
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How might their different structures affect their behavior with DNA?
• Electronic Spectroscopy (UV/vis)• Cyclic Voltammetry (Ered)
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225 275 325 375 425 475 525 5750
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Spectra of All Ru Compounds in Acetonitrile
Ru(bpy)2alloxRu(bpy)2DMARu(bpy)2pterinRu(bpy)2DPPZ
Wavelength (nm)
Abs
orba
nce
(a.u
.)
Electronic Spectroscopy
The Ru complexes are all orange:Won’t their UV/vis spectra be the same?
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Cyclic Voltammetry
A Method to Measure Electrochemical Behavior and Ered
• Will the complexes have different Ru redox potentials?
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The Same Question will be asked of your hemes: Can changing Heme substituents vary Fe(3+/2+) reduction potentials?
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The Cyclic Voltammetry Experiment
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+ current, cathodicic
- current, anodicia
+ potential,
V
- potential,
V
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+ current, cathodicic
- current, anodicia
+ potential,
V
- potential,
V
Reduction
Oxidation
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+ current, cathodicic
- current, anodicia
+ V - V
+1.0 V -1.0 V
When no electroactive species is present, no current flows, no ic nor ia
This is what backgroundelectrolyte should look like.
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+ current, cathodicic
- current, anodicia
+ V - V
+1.0 V -1.0 V
Starting at a + V,Initially no current flows
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+ current, cathodicic
- current, anodicia
+ V - V
+1.0 V -1.0 V
If a reducible species is present ic will increase
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+ current, cathodicic
- current, anodicia
+ V - V
+1.0 V -1.0 V
And continue to increase
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+ current, cathodicic
- current, anodicia
+ V - V
+1.0 V -1.0 V
Until all of the species is reduced. ic has reached a maximum.
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+ current, cathodicic
- current, anodicia
+ V - V
+1.0 V -1.0 V
Then ic decreases until…
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+ current, cathodicic
- current, anodicia
+ V - V
+1.0 V -1.0 V
It again reaches the background current level.
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+ current, cathodicic
- current, anodicia
+ V - V
+1.0 V -1.0 V
Now the potential is reversed
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+ current, cathodicic
- current, anodicia
+ V - V
+1.0 V -1.0 V
And as V is more positive, the reduced species can bere-oxidized
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+ current, cathodicic
- current, anodicia
+ V - V
+1.0 V -1.0 V
So ia decreases to a maximum
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+ current, cathodicic
- current, anodicia
+ V - V
+1.0 V -1.0 V
Where all has been oxidized,
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+ current, cathodicic
- current, anodicia
+ V - V
+1.0 V -1.0 V
Then ia decreases, back to thebackground level.
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+ current, cathodicic
- current, anodicia
+ V - V
+1.0 V -1.0 V
Important features:Ec
Ea
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+ current, cathodicic
- current, anodicia
+ V - V
+1.0 V -1.0 V
E1/2 is ~ EoRed
Ec
Ea
E1/2
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+ current, cathodicic
- current, anodicia
+ V - V
+1.0 V -1.0 V
All Fe(3+)
Using an Fe(3+) heme,Fe is electroactive,(and also the heme!) …
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+ current, cathodicic
- current, anodicia
+ V - V
+1.0 V -1.0 V
A little Fe(2+) formed
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+ current, cathodicic
- current, anodicia
+ V - V
+1.0 V -1.0 V
more Fe(2+) formed
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+ current, cathodicic
- current, anodicia
+ V - V
+1.0 V -1.0 V
Largest cathodic current,Max rate of Fe(2+) formed
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+ current, cathodicic
- current, anodicia
+ V - V
+1.0 V -1.0 V
Little Fe(3+) left; Less Fe(2+) forms;Decrease in ic
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+ current, cathodicic
- current, anodicia
+ V - V
+1.0 V -1.0 V
all Fe(2+) now
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+ current, cathodicic
- current, anodicia
+ V - V
+1.0 V -1.0 V
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+ current, cathodicic
- current, anodicia
+ V - V
+1.0 V -1.0 VA little Fe(2+) isre-oxidized toFe(3+)
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+ current, cathodicic
- current, anodicia
+ V - V
+1.0 V -1.0 V
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+ current, cathodicic
- current, anodicia
+ V - V
+1.0 V -1.0 V
Nearly all Fe(2+) has been oxized
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+ current, cathodicic
- current, anodicia
+ V - V
+1.0 V -1.0 VAll back to Fe(3+).
Cycle could be runagain, many times.
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+ current, cathodicic
- current, anodicia
+ V - V
+1.0 V -1.0 V
Important features:Ec
Ea
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+ current, cathodicic
- current, anodicia
+ V - V
+1.0 V -1.0 V
E1/2 for Fe(3+/2+) reduction
Ec
Ea
E1/2
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theblackbox Working
Electrode:
Where the redox reaction action occurs
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theblackbox
Reference Electrode:
Defines “0” potential for the cell.We use Ag/AgCl
Working Electrode:
Where the redox reaction action occurs
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theblackbox
Auxilliary Electrode:
Needed to complete circuit.
We use a Pt wire
Reference Electrode:
Working Electrode:
Where the redox reaction action occurs
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theblackbox
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…
Working Electrode:
Where the redox reaction action occurs
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theblackboxWorking
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…
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theblackboxWorking
Electrode:
Where the redox reaction action occurs
Fe(2+)Fe(3+) Fe(3+) 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+)
Still moving up the cathodic current peak…
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theblackboxWorking
Electrode:
Where the redox reaction action occurs
Fe(2+)Fe(2+) Fe(3+) 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+)
After the maximum cathodic current peak…
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theblackboxWorking
Electrode:
Where the redox reaction action occurs
Fe(2+)Fe(3+) Fe(3+) 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+)
Moving down the anodic current peak…
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theblackboxWorking
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…
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theblackboxWorking
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…
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+ ic
- ia
- V
In your CV scans of Fe(porphyrin)Cl, you will see:
Interpretation????
+ V
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+ ic
- ia
- V
One more thing:Use of internal reference,ferrocene
E(1/2) values of sample are reported vs. ferrocene(example….)
+ V
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Schedule for Thursday Nov. 1CV UV/vis
1:00 -1:20 Group 1 Group 2
1:20 – 1:35 Group 2 Group 1
1:35 – 1:50 Group 3 Group 4
2:00 – 2:15 Group 4 Group 3
2:15 – 2:30 Group 5 Group 6
2:30 -2:45 Group 6 Group 5
2:45 – 3:00 Group 7 Group 7
After that:3:30 Everyone meet in 264 to discuss results4:15 – Attend Seminar by Dr. Nathanial Nucci
Calculate E(1/2) for your data immediately, both vs. reference and corrected, vs. ferrocene
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How is the range of Heme Potentialsin Respiration adjusted?