2 Feb 2011

The Electronic Properties of tris-(2,2'-bipyridine)-ruthenium(II) Lab Experiment(s)

Lab Experiment

Submitted by Jared J. Paul, Villanova University
Categories
Description: 

This is a lab experiment designed to cover an array of techniques, including metal complex synthesis, spectroscopy and electrochemistry.  Overall, the goal is to synthesize the metal complex Ru(bpy)32+, exchange the counter ion to demonstrate changes in solubility, absorbance and emission properties (including excited state quenching through energy and electron transfer, and ground state oxidation), as well as cyclic voltammetry of the complex.  It is a three week lab: Week 1 - Synthesis of the complex; Week 2 - Electronic spectroscopy of the complex; Week 3 - Electrochemistry of the complex.

AttachmentSize
PDF icon JJP Rubpy Lab.pdf147.49 KB
Learning Goals: 

After this laboratory experiment is complete a student should be able to explain "What are the possible processes that can occur when a molecule absorbs light?" In addition, they should be able to explain the many ways in which electron transfer can occur and different methods of studying electron transfer.

Equipment needs: 

Chemicals: Ruthenium trichloride; 2,2'-bipyridine; NaOH pellets; 31% phosphinic acid; KCl; acetone; ammonium hexafluorophosphate; ether; hydroquinone; quinone; ammonium cerium(IV) nitrate; acetonitrile; tetrabutylammonium hexafluorophosphate; ferrocene Supplies/Equipment: round bottom flask; reflux condenser; hose adapter; stir bar; hot plate; filter; beaker; nitrogen or argon line; IR spectrophotometer; UV/Visible spectrophotometer; Fluorimeter; disposable fluorimeter cells; 5 mL volumetric flasks; potentiostat

Related activities: 
Implementation Notes: 

I have done this laboratory experiment twice. The experiment can be mixed and matched depending upon what you want to do!

Time Required: 
3 weeks - 4 hours labs. The electrochemistry week does not require the whole time.
Evaluation
Evaluation Methods: 

There are a series of questions at the end of the lab that students must address in a full written paper. I have students write a paper in JACS format (the other labs taught in the semester, students write communications in JACS format).

Evaluation Results: 

Overall, student's reports have been good in this area. The course is a writing intensive course. What I've found is that the students perform better when writing their reports as they go through the weeks (as opposed to those students who wait until the last minute and generally forget what they've done). I have not tried this, but I will most likely have students write sections of the paper each week so they get more feedback from me in the process.

Creative Commons License: 
Creative Commons Licence

Comments

This looks great, Jared! I look forward to delving more deeply in a couple years when I'll need to expand my inorganic lab offerings!

Jared,

What about using [Ru(dppz)3]2+ instead of [Ru(bpy)3]2+?

SNC

I used this experiment in my lab this semester and it worked out well!  We also included a discussion on the reducing agent (sodium hypophospinate). Jared provided additional follow up that included a reaction that shows 2e electrons are being generated to reduce Ru3+ to Ru2+. One of my student's asked what is stopping the reduction of Ru+3 to Ru+1 since you have two electrons available. That was a cool question. Although I remembered that +3 and +2 are the common oxidation states for ruthenium, Jared pointed out to me the role of redox potentials. The students loved the precipation of the PF6 salt from solution.  This reaction is a KEEPER for my inorganic lab.

 

Sibrina

This is very nice.  There's also some nice labs that you can do to show applications.  For instance you can use [Ru(bpy)3][BF4]2 to prepare a "organic" LED (http://mrsec.wisc.edu/Edetc/nanolab/index.html) and you can substitute it for raspberry juice in making a Gratzel photovoltaic cell.  The only drawback with the PF6 salt is that it is almost completely insoluble in water.  I've found the BF4- salt to be more flexible.

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