Electron transfer

2 Feb 2011
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.

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.

Corequisites: 
Course Level: 
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.
30 Sep 2010

Inorganic Chemistry of Organ Pipes: Composition and Corrosion

Submitted by Catherine Oertel, Oberlin College
Description: 

This presentation provides an inorganic chemist's perspective on metals used to make organ pipes and their corrosion and conservation.  The slides highlight my own research in this area as well as work being done by other scientists around the world.  The purpose of this learning object is to show students an application of inorganic chemistry that they probably have not encountered before and show an example of how analytical methods of materials chemistry can be used in conservation science.   

The Power Point presentation contains nine slides, including the title slide and a slide with additional references.  The Word file containing accompanying notes provides background information corresponding to each slide.

Prerequisites: 
Course Level: 
Corequisites: 
Learning Goals: 

1.  A student should be able to identify the material that is most commonly used to make organ pipes.

2.  A student should be able to describe the chemical process through which atmospheric corrosion occurs.

3.  A student should be able to give examples of experimental methods that are used to study organ pipe corrosion. 

Implementation Notes: 

This learning object is part of a lecture I have developed on inorganic chemistry in art conservation.  Each year, I devote the final class of the semester in my sophomore/junior-level inorganic chemistry course to this topic.  I briefly introduce some ideas about conservation science and then present several case studies showing questions about artifacts or problems of deterioration that have been addressed through scientific analysis.  These include studies of paint discoloration on a portrait and the conservation of a wrecked ship as well as my work on organ pipe corrosion.  I intend this last-class lecture to be interesting and enjoyable, and I let students know that I don't expect them to take in all the details as they might in a normal lecture.  I do point out that during the lecture, we'll briefly touch on and review many inorganic chemistry topics from the semester.

Information about the other case studies and the introduction to conservation science are to come in future "Five Slides" installments!

Evaluation
Evaluation Methods: 

Because of the recreational nature of my last-class lecture, I have not created a problem set to accompany it.  As an exam question, I have asked students to identify the redox reactions involved in atmospheric corrosion.

29 Sep 2010

Cyclic voltammetry

Submitted by Chip Nataro, Lafayette College
Description: 

This is a short presentation on cyclic voltammetry. It is covers the basics and some simple electrode mechanisms. There is room for improvement (especially in my art) and suggestions are welcome.

Course Level: 
Prerequisites: 
Corequisites: 
Learning Goals: 

A student should be able to

1) describe the experimental set-up of a three electrode cyclic voltammetry experiment,

2) explain what information can be obtained from a cyclic voltammogram, and

3) describe simple electrode mechanisms.

Subdiscipline: 
27 Aug 2010
Evaluation Methods: 

The students’ written answers to the questions and presentations of the questions were graded.

Evaluation Results: 

Students answered the questions well.  If anything, this series of questions may be too “easy” for senior-level students.  I hope to increase the level of difficulty in the future.

Description: 

In the two years since this article was published, it has jump-started a large amount of research in the area of cobalt-based catalysts for solar water splitting.  The paper describes the electrochemical synthesis and oxygen-evolution capabilities of a Co-phosphate catalyst under very mild conditions.  The paper can stimulate discussion of many topics found in the inorganic curriculum, including electrochemistry, semiconductor chemistry, transition metal ion complex kinetic trends, and solid state and electrochemical characterization techniques.

Corequisites: 
Prerequisites: 
Learning Goals: 

After reading and discussing this paper, a student should be able to:

•    explain, using concepts of electrochemical potential and band theory, how semiconductors can be used to generate hydrogen fuel from sunlight and water.
•    describe the desirable characteristics of an oxygen-evolving catalyst and explain why this catalyst is a marked improvement over existing materials.
•    follow the oxidation/reduction cycle of the cobalt ion as it goes from solution to the catalyst compound and then back into solution.
•    characterize the cobalt ion as inert or labile based on its d electron count and relate the kinetic trends to the self-repair mechanism proposed in the article.

Implementation Notes: 

This learning object was developed as one of five journal article discussions included in a small (5 student) senior-level inorganic course in the spring of 2010.  This course is the only inorganic course (aside from a separate inorganic laboratory) offered in our curriculum.  The ten questions included here are not nearly comprehensive and can be considered a jumping-off point for further development.  In particular, the last question could be extended to ask students to read and briefly present the results of one of the articles that has referenced this paper.  Research in this field has been advancing rapidly.

The literature discussions were interspersed throughout the semester.  In each case, students read the article and answered the questions before coming to class, then presented select questions in teams of two or three to the rest of the group.  

Time Required: 
20-25 minutes as implemented. A larger class might take more time.
17 Jul 2010
Evaluation Methods: 

Upon completion of the experiment the student pairs submit a brief summary of their results and plans to developing a formal report. A draft report is then written in the style and format of an American Chemical Society journal article; the draft must be thoroughly referenced. The instructor reads the draft and returns it to the students with suggestions for revisions. The final version of the report is evaluated in accord with criteria presented in the policy section of the laboratory manual.

 

Evaluation Results: 

Given the integrated nature of this exercise, the laboratory reports indicate whether or not the students have mastered the essential ideas of coordination chemistry. The reports reveal skill in laboratory technique through the percent yield and quality of the products and recording infrared and electronic absorption spectra and in interpretation of the spectra. Although reports are often of high quality and reflect considerable insight, some students seem not to grasp the distinction between molecular and electronic structure. A somewhat larger number have difficulty synthesizing the reaction observations and the measurements, computation, and database results into a comprehensive narrative. That requires further discussion with the instructor. Many students need to learn when to reference statements appropriately.

Description: 

This experiment, intended for an upper-level inorganic chemistry course, involves classical transition-metal coordination compounds. The purpose of the exercise is to compare the physical and chemical properties of coordination complexes containing copper(II) and silver(II) ions bound to the anion of pyridine–2–carboxylic acid, also known as picolinic acid, picH. The metallic elements copper and silver are in the same family in the periodic table, but their chemical properties are quite different. Although Cu(II) is the stable oxidation state in aqueous solution, Ag(II) is powerfully oxidizing in water. The conjugate base of picH, pyridine–2–carboxylate or picolinate ion, acts as a ligand toward these metal ions, binding to them in chelating mode through the pyridine ring nitrogen atom and one of the carboxylate oxygen atoms. The compounds are synthesized in water at room temperature. In both cases picolinic acid is deprotonated to give picolinate ion, which then binds to Cu2+ and Ag2+, yielding products formulated as M(pic)2. For silver, Ag+ must be oxidized to Ag2+. Molecular and electronic structural characterization is accomplished through infrared, electronic absorption, and electron spin resonance spectroscopy and density functional calculation. Available crystal and molecular structure information is surveyed using the Cambridge Structure Database. 

Prerequisites: 
Course Level: 
Subdiscipline: 
Learning Goals: 

• Students will discover that two structurally similar transition metal compounds can be synthesized cleanly from water solutions.

• Students will engage in the molecular and electronic structural characterization of both compounds. They should appreciate the need to employ a variety of physical measurements to develop a comprehensive structural understanding of a molecule.

• Students will develop an appreciation of differences arising from position in the first vs. second vs. third transition series (the gold(II) compound does not exist).

• Students will learn to do an electronic structure calculation on a transition metal compound and to explore a crystallographic database.

Equipment needs: 

• Pyridine-2-carboxylic acid (picolinic acid), copper(II) acetate hydrate, silver(I) nitrate, ammonium peroxodisulfate, sodium carbonate, deionized water

• Beakers, magnetic stirrers, magnetic stirring bars, filtering funnels, filtering, vacuum drying capability, vials

• FTIR spectrometer (mineral-oil/NaCl or KBr disks or KBr and press for pellet making), UV/Visible spectrometer (quartz cell, water), ESR spectrometer (quartz tubes)

• Access to density functional theory computation software (Spartan, for example) and to Cambridge Structure Database

Implementation Notes: 

Students do this experiment in pairs. The synthetic reactions are easily accomplished. The copper reaction gives either the anhydrous material or the monohydrate. The reaction filtrate will yield large crystals, but this requires several weeks at room temperature. The silver compound that does not precipitate from the initial reaction will decompose in solution within a few days at ambient temperature. We store the silver compound in a refrigerator and allow the storage vial to warm to room temperature before removing a sample for physical measurements. The IR measurements are straightforward. We record both solid-state and solution electronic absorption spectra for comparison with the IR spectra (solid state) and to obtain molar absorptivity values. Both compounds give strong ESR spectra for solid-state samples, and a procedure for data analysis is provided. The density functional calculation for the copper compound works well using low-level Spartan software; for silver the number of electrons is too large for successful calculation. Students should understand that generally the simple Spartan DF computation applies to the molecules in the gas phase.

Time Required: 
• One and a half hours for syntheses by a pair of students. • Two-three hours for spectroscopy.
26 May 2010

Battery in class activity

Submitted by Sheila Smith, University of Michigan- Dearborn
Evaluation Methods: 

Since this is an in-class activity, no assessment is typically performed because we go through the solutions during the class period. I have occasionally collected clicker results for some of the numerical questions to encourage students to really work at solving it on their own. The usefulness of the exercise can be measured in the quality of the discussion that is generated.

Description: 

This is an in-class exercise to be used at the end of General Chemistry (II).  I use it as a capstone exercise at the end of my second semester genchem course, but it would also make an excellent introductory review exercise at the beginning of a junior level inorganic course.  It provides an excellent review of topics from the entire semester (electrochemistry, acid-base, thermodynamics, colligative properties, solution chemistry and calculations) and shows how they are inter-related in a real world application (a car battery).

Learning Goals: 

• A student should be able to dissect the shorthand notation for a voltaic cell and convert that to a balanced redox equation in acidic conditions. • A student should be able to use the Nernst equation to calculate the potential of the battery at non standard conditions. • A student should be able to apply Hess' Law to calculate basic thermodynamic properties for a balanced equation. • A student should be able to calculate concentration of solutions, and to discuss the applicability of these different units. • A student should be able to use his/ her knowledge of colligative properties (both concept and calculation) to discuss the effect of temperature on a battery. • A student should be able to apply his/her knowledge of LeChatelier's Principle to make predictions about the effect changes in conditions will have on the state of a battery.

Corequisites: 
Prerequisites: 
Course Level: 
Equipment needs: 

none

Subdiscipline: 
Time Required: 
1 class period
20 Jan 2010

Metals in Biological Systems - Who? How? and Why?

Submitted by Elizabeth Jamieson, Smith College
Description: 

This learning object was developed collaboratively by members of the IONiC Leadership Council.  The overall goal is to provide a general overview of metals in biological systems and introduce students to several of the important ideas in the field of bioinorganic chemistry.  Topics include toxic metals, metals used in biological systems and the overlap of these categories; issues associated with the uptake, transport and storage of metal ions; and the benefits gained by using metals in biological molecules.  

The learning object includes a PowerPoint presentation (with various animations).  There are notes included in the PowerPoint file for each slide providing additional background and details to introduce in class.  For convenience, the notes from the PowerPoint file have also been placed in a separate Word document.

Prerequisites: 
Corequisites: 
Learning Goals: 

Learning goals for these slides include:

1.  Students will be able to give examples describing the "problem" of metals in biology: lack of bioavailability, toxicity and the importance of getting it just right.

2. Students will be able to give three reasons (with specific examples) of why metal binding and transport is important.

     Metals have to be accumulated in the body (you can't make metals and they're not naturally prevalent).

     They must be stored in inert forms (because they're toxic).

     They must be present above a threshold to support life (metals must get in and out).

3. Students can use their knowledge of VSEPR to describe structures likely in bioinorganic systems.

4. Students can use their knowledge of Lewis acid-base chemistry to describe reactivity in bioinorganic systems.

 

Implementation Notes: 

These slides could be used to give students a sense of the problems and benefits of using metals in biological systems as a way to introduce important ideas in bioinorganic chemistry.  Many of the ideas, for example metal ion transport & storage, also have the potential to be expanded upon, with details from a text on bioinorganic chemistry or examples from the current literature.

Time Required: 
Approximately 1 class (or more if one chose to expand on the topics)
Evaluation
Evaluation Methods: 

Students could be asked to provide some of the information presented in the "Learning Goals" section above as part of an exam or quiz question.  

Evaluation Results: 

This learning object was developed collaboratively by members of the Leadership Council who teach these topics in class regularly.  In general, we have found that students are interested in learning how metals are used in biological systems.  The issue of toxicity is always interesting since students do not always realize that you can have too much of a good thing (too much Fe can be toxic, for example).  We have found that students enjoy seeing how topics they have already learned, like acid/base and redox chemistry, are applicable in biology.

6 Jul 2009

Energy Nuggets: Engineering Viruses to Build a Better Battery

Submitted by Maggie Geselbracht, Reed College
Evaluation Methods: 
At the end of the discussion, I collected the students’ written answers to the discussion questions and evaluated them mostly on effort.
Evaluation Results: 
This activity came at the very end of the semester, so the level of effort was somewhat sporadic.  However, most students seemed to really like reading this article, even if it was challenging to figure out the science.  None of the students could figure out all of the details of how to calculate the lithium ion capacity of the anode material, although many of them had correctly completed several of the steps along the way.  So, we went though the whole calculation on the board, obtaining slightly different results than what was in the paper (either a typo or unidentified calculation error on our part). 
Description: 
This literature discussion activity is one of a series of “Energy Nuggets,” small curricular units designed to illustrate: The Role of Inorganic Chemistry in the Global Challenge for Clean Energy Production, Storage, and Use.

Renewable energy is great, but what do we do when the sun doesn’t shine and the wind doesn’t blow?  This paper describes a novel approach to building a better battery by using viruses to self-assemble nanoscale battery materials.  Angela Belcher’s group at MIT focuses in this paper on self-assembly of the anode material for rechargeable lithium ion batteries, and the improvements that are possible with the nanoscale architecture.  In a very recent paper (citation below), Belcher’s group has used virus-enabled synthesis to also assemble the cathode material, although this recent work was not yet available at the time of our class discussion.  An excellent review paper on the challenges of building a better lithium ion battery by Jean-Marie Tarascon can also be provided to give students a broader overview of the field.

Prerequisites: 
Course Level: 
Learning Goals: 

After reading these papers and working through the discussion questions, a student will be able to:

  • Describe the basic components of a rechargeable lithium ion battery and the redox reactions that occur at the anode and cathode upon cycling.
  • Discuss the motivation of Belcher’s group to use viruses and genetic engineering to build a better battery material and the variety of evidence that these scientists have achieved their goal.
  • Discuss the pros and cons of highly interdisciplinary work including bridging the challenges of language and jargon.


Implementation Notes: 
With a relatively weak background in molecular biology myself, I relied a lot on the knowledge of my students to help translate the “biospeak” in this paper.  Prior to our class discussion, a few students posted basic questions on our class discussion forum such as “what is a phage display library?” and others tried to answer them.  It was more effective to just spend a few minutes at the beginning of the class discussion defining terms.  I invited a biochemistry colleague to read the paper and sit in on the discussion also, and he was very helpful in clarifying many of the concepts.
Time Required: 
50 minutes
6 May 2009

Henry Taube and Electron Transfer

Submitted by Bradley Wile, Ohio Northern University
Evaluation Results: 

Students seem to like the article. Many comment that Henry Taube has an extraordinary moustache!

Description: 

When teaching reactions and mechanisms of inorganic complexes, I tend to get to the end of the chapter (out of breath) and find myself thinking "*$#&, I forgot about electron transfer". While I think it is important that students get an understanding of this in an upper level inorganic course, I simply don't have, or forgot to budget the time to really talk about it.

I give them a brief rationale for why one would want to study mechanisms of electron transfer ("Remember all those redox reactions you balanced back in first year? Are you curious how those electrons moved around?"), and hand out/refer them to an excellently written retrospective on the career and research of Henry Taube (see link below).

I found this Inorganic Chemistry Viewpoint article to be very "readable", without sacrificing chemical detail (the nitty gritty). I breifly highlight some of the interesting points (Co3 + Cr2 --> Co2 + Cr3), and encourage them to read on to learn more about the career of a Nobel Prize winning inorganic chemist.

Topics Covered: 
Corequisites: 
Course Level: 
Learning Goals: 

Students should gain an understanding of the mechanisms for electron transfer. One of the other main goals for this reading is to have the students learn and appreciate the history of the field. I try to highlight the logical progression of research goals, and this article demonstrates the influence of Taube's early years on the research conducted later.

Subdiscipline: 
12 Jan 2009

House: Inorganic Chemistry

Submitted by Adam R. Johnson, Harvey Mudd College
Description: 

House (Inorganic chemistry):  The book is divided into 5 parts:  first, an introductory section on atomic structure, symmetry, and bonding; second, ionic bonding and solids; third, acids, bases and nonaqueous solvents; fourth, descriptive chemistry; and fifth, coordination chemistry.  The first three sections are short, 2-4 chapters each, while the descriptive section (five chapters) and coordination chemistry section (seven chapters covering ligand field theory, spectroscopy, synthesis and reaction chemistry, organometallics, and bioinorganic chemistry.) are longer.  Each chapter includes references (both texts and primary literature) for further reading, and a few problems (answers not available in the back of the book). 

I thought the text was generally good.  This text felt aimed at the introductory one-semester inorganic course offered at most schools rather than an advanced (senior/grad) course.  Although MO theory is developed in the text, most of the coordination chemistry is described using crystal field theory, though a short section on MO theory for complexes is included.  The sections on descriptive chemistry of the elements are very good and not overloaded with too much information, and the writing style (throughout the text) is easy to read and conversational.

My main complaint about the book, and this may seem petty, is that the molecular orbitals (throughout) do not accurately depict the way actual orbitals look;  they are too "pointy." 

The list price for the student text is $99.95 for a paperback, 864p version.

Prerequisites: 
Corequisites: 
Course Level: 

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