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?

How might their different structures affect their behavior with DNA?

• Electronic Spectroscopy (UV/vis)• Cyclic Voltammetry (Ered)

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)

Ab

so

rba

nc

e (

a.u

.)

Electronic Spectroscopy

The Ru complexes are all orange:Won’t their UV/vis spectra be the same?

Cyclic Voltammetry

A Method to Measure Electrochemical Behavior and Ered

• Will the complexes have different Ru redox potentials?

The Same Question will be asked of your hemes: Can changing Heme substituents vary Fe(3+/2+) reduction potentials?

The Cyclic Voltammetry Experiment

+ current, cathodicic

- current, anodicia

+ potential,

V

- potential,

V

+ current, cathodicic

- current, anodicia

+ potential,

V

- potential,

V

Reduction

Oxidation

+ 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.

+ current, cathodicic

- current, anodicia

+ V - V

+1.0 V -1.0 V

Starting at a + V,Initially no current flows

+ current, cathodicic

- current, anodicia

+ V - V

+1.0 V -1.0 V

If a reducible species is present ic will increase

+ current, cathodicic

- current, anodicia

+ V - V

+1.0 V -1.0 V

And continue to increase

+ current, cathodicic

- current, anodicia

+ V - V

+1.0 V -1.0 V

Until all of the species is reduced. ic has reached a maximum.

+ current, cathodicic

- current, anodicia

+ V - V

+1.0 V -1.0 V

Then ic decreases until…

+ current, cathodicic

- current, anodicia

+ V - V

+1.0 V -1.0 V

It again reaches the background current level.

+ current, cathodicic

- current, anodicia

+ V - V

+1.0 V -1.0 V

Now the potential is reversed

+ current, cathodicic

- current, anodicia

+ V - V

+1.0 V -1.0 V

And as V is more positive, the reduced species can bere-oxidized

+ current, cathodicic

- current, anodicia

+ V - V

+1.0 V -1.0 V

So ia decreases to a maximum

+ current, cathodicic

- current, anodicia

+ V - V

+1.0 V -1.0 V

Where all has been oxidized,

+ current, cathodicic

- current, anodicia

+ V - V

+1.0 V -1.0 V

Then ia decreases, back to thebackground level.

+ current, cathodicic

- current, anodicia

+ V - V

+1.0 V -1.0 V

Important features:

Ec

Ea

+ current, cathodicic

- current, anodicia

+ V - V

+1.0 V -1.0 V

E1/2 is ~ EoRed

Ec

Ea

E1/2

+ 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!) …

+ current, cathodicic

- current, anodicia

+ V - V

+1.0 V -1.0 V

A little Fe(2+) formed

+ current, cathodicic

- current, anodicia

+ V - V

+1.0 V -1.0 V

more Fe(2+) formed

+ current, cathodicic

- current, anodicia

+ V - V

+1.0 V -1.0 V

Largest cathodic current,Max rate of Fe(2+) formed

+ current, cathodicic

- current, anodicia

+ V - V

+1.0 V -1.0 V

Little Fe(3+) left; Less Fe(2+) forms;Decrease in ic

+ current, cathodicic

- current, anodicia

+ V - V

+1.0 V -1.0 V

all Fe(2+) now

+ current, cathodicic

- current, anodicia

+ V - V

+1.0 V -1.0 V

+ current, cathodicic

- current, anodicia

+ V - V

+1.0 V -1.0 VA little Fe(2+) isre-oxidized toFe(3+)

+ current, cathodicic

- current, anodicia

+ V - V

+1.0 V -1.0 V

+ current, cathodicic

- current, anodicia

+ V - V

+1.0 V -1.0 V

Nearly all Fe(2+) has been oxized

+ current, cathodicic

- current, anodicia

+ V - V

+1.0 V -1.0 V

All back to Fe(3+).

Cycle could be runagain, many times.

+ current, cathodicic

- current, anodicia

+ V - V

+1.0 V -1.0 V

Important features:

Ec

Ea

+ current, cathodicic

- current, anodicia

+ V - V

+1.0 V -1.0 V

E1/2 for Fe(3+/2+) reduction

Ec

Ea

E1/2

theblackbox Working

Electrode:

Where the redox reaction action occurs

theblackbox

Reference Electrode:

Defines “0” potential for the cell.

We use Ag/AgCl

Working Electrode:

Where the redox reaction action occurs

theblackbox

Auxilliary Electrode:

Needed to complete circuit.

We use a Pt wire

Reference Electrode:

Working Electrode:

Where the redox reaction action occurs

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

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…

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…

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…

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…

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…

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…

+ ic

- ia

- V

In your CV scans of Fe(porphyrin)Cl, you will see:

Interpretation????

+ V

+ ic

- ia

- V

One more thing:Use of internal reference,ferrocene

E(1/2) values of sample are reported vs. ferrocene(example….)

+ V

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

How is the range of Heme Potentialsin Respiration adjusted?