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Laboratory Project Summary:
Students in an upper level Inorganic Chemistry lab course are given a choice between two final lab projects. Both projects involve the synthesis of visible light-absorbing ruthenium complexes, however the subsequent application of these complexes correspond to different subfields within inorganic chemistry. This feature allows them to pursue a project that continues to develop their synthetic, data-analysis, and writing skills while pursuing one that most closely aligns with their interests.
Using skills they have been developing throughout the semester, the students use published literature as a guide to design their own experimental procedures for their given project and plan a multi-day schedule for accomplishing synthesis, characterization, and application of chosen complex. A final write-up in the writing style and formatting of a full publication in Inorganic Chemistry ties together their background research and their experimental results and discussion into a professional package.
Descriptions of Specific Project Choices:
The first project choice involves the synthesis of a Ruthenium photosensitizer dye (N719) for use in constructing a working solar cell. This project is directed towards students who are interested in applications of inorganic chemistry to materials and devices as well as energy-related research. Students are provided literature citations to look up to help them explore how dye-sensitized solar cells work, and then plan and perform the synthesis of of the photosensitizer dye. Following its synthesis and purification, the dye's structure is confirmed via IR and NMR techniques, and its relevant photochemical properties observed via UV-Vis spectroscopy. Finally, the student constructs a dye-sensitized solar cell using their synthesized dye and characterize the cell by plotting I-V curves of its behavior in bright light under different resistive loads.
The second project choice involves the synthesis of a modern ruthenium photoredox catalyst (Ru(bpy)3Cl2) to then use as such a catalyst in a decarboxylative radical fluorination reaction. This project is targeted at using organometallic complexes as catalysts and is more directed towards students who are interested in catalysis, organic synthesis, and medicinal chemistry. Students are provided literature citations to look up to help them explore the fundamentals of photoredox catalysis, and then plan and perform the synthesis of the Ru(bpy)3Cl2 catalyst. Following its synthesis and purification, the dye's structure is confirmed via IR and NMR techniques, and its relevant photochemical properties observed via UV-Vis spectroscopy. Finally, the student uses their freshly made catalysis to carry out a synthetically useful fluorination reaction (involving oxidative decarboxylation triggered by the catalyst), followed by isolation and characterization of their fluorinated product.
This project description and materials can hopefully also serve as a general guide towards constructing and implementing your own lab projects based around literature reports of modern chemistry that could be of interest to your students.
| Attachment | Size |
|---|---|
| Solar Cell Experimental Guidelines_1.pdf | 284.98 KB |
| Solar Cell Project Implementation and Setup Notes_1.pdf | 330.83 KB |
| Photoredox Experimental Guidelines_0.pdf | 406.1 KB |
| Photoredox Project Implementation and Setup Notes_0.pdf | 292.37 KB |
The goals of this project are:
1. To independently do background research on a topic and repeat/modify literature procedures.
2. To carry out synthetic procedures using techniques developed over the semester (air-free synthesis techniques, various purification and characterization techniques).
3. To apply a synthesized organometallic complex to a device or reaction of practical use.
4. To produce professional, publication-quality writing based on their independent background research (for the introduction) and their experimental results and discussion.
General Synthetic Equipment and Analytical Instrumentation:
Schlenk lines (or some other means to carry out moderately air-free synthesis)
Rotary Evaporator
UV-Vis spectrophotometer
NMR
IR spectrometer (not necessary, though useful if trying to obtain and process all of the required spectra a publication would require)
Specifically for the solar cell project:
ITO-doped glass slides
Multimeter(s)
Variable resistor box
Wires with alligator clamps
A white lamp
Specifically for the photoredox project:
Bright blue LED lamp (such as a Kessil 456 nm photoreaction lamp)
A light shield (could just be a propped up cardboard box, or something more sophisticated. This is important as the high wattage blue LED's are a safety hazard to the eyes)
More details on setups for specific projects can be found in the relevant attached files.
Safety considerations:
Any waste containing nitric acid should be kept separate from any other waste. Organics and nitric acid should never be mixed.
Any light sources are a potential danger to the eyes, and the bright blue LED lamps are very dangerous. Blue light safety glasses should be used near the light source, one should never look directed at the light, and the area around the lamp should be shielded with a light shield when turning on the lamp and for the duration of its usage.
Normal safety precautions with chemical handling in research labs should be adhered to.
Chemicals:
The di-ester bipyridine ligand used for the first step of the N719 dye synthesis is not commercially available (at least not at a reasonable cost). It needs to be synthesized from the Fischer esterification of 4,4'-dicarboxy-2,2'-bipyridine (CAS: 6813-38-3) and isobutyl alcohol.
The aryloxyacetic acid starting material for the photoredox-catalyzed fluorination reaction also needs to be synthesized, via an SN2 reaction of 4-phenylphenol (CAS: 92-69-3) and ethyl bromoacetate (CAS: 105-36-2), followed by basic hydrolysis of the ester to the acid.
There are several options for making these starting material:
1. If there is time in your semester schedule, the students could make these themselves (though that has not been a practical solution in my course).
2. The instructor or TA's can make them themselves. (I have done this)
3. These are simple reactions that are good for a new research student to perform as some of their first reactions when joining a research lab. (I have done this)
4. Because these reactions are simple reactions seen in Organic Chemistry lecture, it may be possible to implement these into an Organic Chemistry laboratory course and collect the products for use in the later senior lab course. This is likely not possible for large lab courses (cost of materials would be too high, and these reactions need to be carried out over multiple days), however it could be possible for smaller lab courses (such as majors/honors sections or in an upper-level organic chemistry lab course).
Project-Specific Implementation/Setups:
Individual documents are provided as attachments. These include the variable resistance setup for generating I-V curves and information on setting up a photoreactor for the photoredox project.
Evaluation
Students are evaluated on their pre-laboratory preparation prior to the first day of their projects, followed by a more complete evaluation in the form of their final journal publication-style write-up.
Students average ~25/30 score on the pre-lab assignments. Usually each students will require the instructor to clear up one or two conceptional of procedural points before they start the project.
Students often perform better on this project's written paper assessment compared to earlier ones, as it is later in the semester and they have been working on their writing throughout.
Feedback from this project is usually quite positive. Some student comments:
"Having [this lab] be almost completely independent was nice"
"Independence and flexibility and looking and multiple procedures and deciding what parts to do was fun"
"I liked the freedom of work/planning as well as the more clear-cut application through hands-on activity"
"My favorite lab was the solar cell, because we made something useful in lab with our product instead of talking about its uses"
"I liked the fluorination lab because I have always wanted to try photoredox catalysis and got the opportunity to!"