Electrochemistry

16 Jul 2014

A Redox-Activated MRI Contrast Agent that Switches Between Paramagnetic and Diamagnetic States

Submitted by Vivian Ezeh, Clemson University, Department of Chemistry
Evaluation Methods: 

The success of the discussion will be evaluated by completing the take home study and the quality of the in-class discussion

Description: 

Students are asked to read an article detailing the development of a cobalt-based MRI contrast agent ("A Redox-Activated MRI Contrast Agent that Switches Between Paramagnetic and Diamagnetic States", Tsitovich, P. B.; Spernyak, J. A.;  Morrow, J. R. Angew. Chem. Int. Ed. 201352, 14247-14250,  DOI: 10.1002/anie.201306394). Before coming to class the students are asked to answer a series of questions designed to guide them through the first half of the article, and to be prepared to discuss their answers in class. During class, the answers of the questions are briefly reviewed before addressing a second set of questions in class.

Course Level: 
Corequisites: 
Learning Goals: 

1) Students explore the coordination geometry of a hexadentate N-donor ligand
2) Students pratice deriving a crystal field orbital diagram from the  magnetic properies of Co(II)/Co(III) complexes
3) Student recognize and understand the origin of the differences of 1H-NMR spectra for paramagnetic and diamagnetic complexes
4) Students understand the basic principles of how a paraCEST contrast agent works, and develop a sense of how to decide on the suitability of a metal complex as a paraCEST contrast agent based on experimental data.
5) Students become more adept at interpreting representations of data

Implementation Notes: 

This reading guide accompanies A Redox-Activated MRI Contrast Agent that Switches Between Paramagnetic and Diamagnetic States, Tsitovich, P. B.; Spernyak, J. A.;  Morrow, J. R. Angew. Chem. Int. Ed. 201352, 14247-14250,  DOI: 10.1002/anie.201306394

The LO is designed to help guide students through the reading of a scholarly article and prepare them for in-class discussion after completing the reading. 

Time Required: 
50 mins
10 Jun 2014

Protein Electrochemistry 3rd Bioinorganic Workshop

Submitted by Sheila Smith, University of Michigan- Dearborn
Description: 

This is a 90 minute talk by Fraser Armstrong of Oxford University (http://armstrong.chem.ox.ac.uk) explaining the electrochemistry of proteins immobilized on surfaces.  The talk was presented at the 3rd Bioinorganic Workshop in 2014 at Pennsylvania State University.  The talk contains an excellent basic tutorial on simple electron transfer on immobilized substrates using simple iron sulfur proteins as the primary example.  Talk continues on to more complicated subject matter including trumpet plots, electrocatalysis by enzymes focusing on the hydrogenases as an example.  The talk concludes with case studies presented on NiFe Hydrogenases, FeFe hydrogenases, and CO dehydrogenase.

Course Level: 
Corequisites: 
Learning Goals: 

The student should be able to explain the information available from electrochemistry on immobilized proteins.

Implementation Notes: 

This is an excellent presentation by the developer of many of the modern techniques for electrochemistry on immobilized proteins.  

Time Required: 
90 minute
25 Jun 2013
Evaluation Methods: 

Students write a formal report which is evaluated with respect to whether each learning goal is achieved.

Evaluation Results: 

Earlier versions of this project have been assigned to approximately 30 students in three senior-level inorganic chemistry courses over a six year period, with substantial revisions made each time. Students were generally able to reproduce the literature results successfully and to gauge which method is expected to be most reliable for first-principles calculations of redox potentials. There was some variability in students’ choice of fullerenes which appropriately span the range of interest. Some students were able to make fairly sophisticated suggestions for future work. 

Description: 

In this project students are asked to reproduce published calculations of molecular orbital energies of a series of derivatized fullerenes and correlate them with published reduction and oxidation potentials obtained from cyclic voltammetry. The particular subset of the derivatives to be studied are chosen by the student and this choice is part of the learning activity. The students then carry out additional calculations using other theoretical models to see whether they improve the correlation between computed and experimental properties. Interpretation of the trends and suggestions for additional work are discussed in a formal report. 

Corequisites: 
Learning Goals: 

After completing this project, students will be able to

  • Summarize the use of cyclic voltammetry to measure redox potentials;
  • Use computer software to build and visualize molecular models of derivatives of buckminsterfullerene;
  • Carry out density functional theory and semiempirical calculations of buckminsterfullerenes;
  • Discuss how derivatization affects the energies of the frontier orbitals;
  • Implement different theoretical models and correctly choose the one which best correlates with the experimental data;
  • Discuss which computational method is likely to be most useful in the prediction of redox potentials from first principles; and
  • Write a formal report describing their findings.
Course Level: 
Equipment needs: 

Modern computer workstation with 6+ GB RAM; molecular structure building and visualization software; quantum mechanics software. Spartan 8 has all of the capabilities required for this project.

 

Implementation Notes: 

The models are built and the calculations are carried out at our institution using Spartan 10, but Gaussian, GAMESS, Q-Chem, NW-Chem or other programs with similar capabilities could be used instead. 

Time Required: 
Students are asked to complete this as an independent project, although the work could be done as a group in one or two laboratory periods if a computer classroom is available.
19 Jul 2012

Electrocatalysis and Proton Reduction

Submitted by Matt Whited, Carleton College
Description: 

These slides provide a brief introduction to the concept of electrocatalysis using the glyoximato cobalt catalysts for hydrogen production recently examined by Peters, Gray, and others.  They provide a suitable introduction to the topic for students interested in reading the primary literature on these topics.

Prerequisites: 
Corequisites: 
Subdiscipline: 
Learning Goals: 
  • A student should be able to define what an electrocatalyst is and the general mechanism by which an electrocatalyst operates.
  • A student should be able to identify a cyclic voltammetric trace corresponding to an operating electrocatalyst and explain why it is different from the electrochemistry of the same complex in the absence of substrate.
  • A student should be able to identify the important features in evaluating the efficiency of an electrocatalyst and define the term "overpotential".
Implementation Notes: 

This set of slides is recommended as background reading (or in-class presentation) for students working on the LO developed from the Valdez et al. PNAS paper "Catalytic hydrogen evolution from a covalently linked dicobaloxime" (the LO is referenced above).

Time Required: 
10-15 minutes
19 Jul 2012
Evaluation Methods: 

Collect responses to questions not covered in class.

Grade class participation.

Assign a more in depth question on an exam. 

Description: 

This learning object was developed at the 2012 NSF sponsored cCWCS VIPEr workshop at UNC-CH where we were fortunate to hear Jillian Dempsey present this research that has appeal to students. This work focuses on an exciting and promising strategy to develop new technology to support a solar energy economy. This literature discussion leads students through a current application in the field of electrocatalysis. The primary literature article for the discussion is found in Proc. Natl. Acad. Sci. USA 2012 109 (39) 15560-15564.

Corequisites: 
Prerequisites: 
Learning Goals: 

Students should be able to:

- identify the chemical reaction presented and balance the half reactions for water splitting

- explain the role of a catalyst in an electrochemical reaction

- propose and evaluate the validity of possible mechanisms based on the experimental data

- find and rationalize trends in the series of catalysts presented in the article

- identify the features associated with electrocatalysis

Subdiscipline: 
Implementation Notes: 

The intent of this literature discussion is geared to provide a broad introduction to the field of electrocatalysis.

Two implementation strategies we thought of are:

  1. Have the students read the article, answer questions 1-4, and watch Chip Nataro’s 5-slides about cyclic voltammetry. In class, discuss questions 5 and 6. For a more in depth discussion, assign questions 7-11.
  2. Have the students read the article and watch Chip Nataro’s 5-slides about cyclic voltammetry the night before. Discuss questions 1-4 in class and assign the questions 5 and 6 for homework.


For a more in depth discussion on electrocatalysis we included a more challenging questions in our document (7-11). These questions could also be used on exams.

Time Required: 
1 class period
9 May 2012

VIPEr Screencast

Submitted by Chip Nataro, Lafayette College
Evaluation Methods: 

If we can attract one person to VIPEr through this screencast it has been successful.

Evaluation Results: 

When I first created this screencast, the VIPEr administrators seemed to enjoy it.

Description: 

This screencast is a brief introduction to some of the features of VIPEr.

Topics Covered: 
Prerequisites: 
Corequisites: 
Learning Goals: 

Publicity, pure and simple.

Course Level: 
Implementation Notes: 

I would not use it in my teaching, but I hope it teaches others to visit VIPEr.

Time Required: 
5 minutes and 30 seconds
21 Sep 2011

How does changing solvent affect redox potential?

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

Students are evaluated based on their participation in the in class discussion. Students can be asked a similar test question.

Evaluation Results: 

I suspect that my gen chem students would do better on this exercise (since they are still fully immersed in the topic) than my senior level bioinorganic students, many of whom have forgotten how to balance redox equations. Students did well with the application of the Nernst equation; they seem to retain more about math than concepts from redox. Students seemed interested by the discussion of how changing pressures of O2 in venous vs arterial blood, could shift potentials further. I may incorporate this into the exercise in the future

Description: 

There are three ways to modulate the redox potential of a metalloenzyme:  Changing ligands, changing geometry, and changing solvent. When I introduce this topic in Bioinorganic, I try to give my students concrete examples of each.  I love this one because it applies what they learned in Gen Chem about the Nernst Equation to a biological problem.  Granted, I don't use a metalloenzyme as my example, but I do pull the biological chemistry into it at the end, by referrring to the cytochrome oxidase/O2 couple.  

In a Gen Chem class this could be used as an in class exercise or a (challenging) test question. 

Learning Goals: 

General Chemistry

  • A student should be able to balance a redox half-reaction in either acidic or basic conditions.
  • A student should know the conditions defined as standard conditions in aqueous electrochemical cells.
  • A student should understand the connection between the Nernst equation and potentials for reactions at other than standard conditions.
  • A student should be able to calculate the cell potential from two half-reaction potentials. 
  • A student should be able to explain the connection between redox potential and strength as an oxidizing (or reducing) agent.
  • A student should be able to calculate the free energy derived (or cost) from a given redox couple. 

 Advanced

  • A student should be able to relate these calculations to the affect of changing solvent (either pH, or concentrations of substrate or even availability of water in a microenvironment around the active site of a metalloenzyme) on the redox potential (and therefore the free energy of a biological redox couple).
Corequisites: 
Equipment needs: 

calculators

Prerequisites: 
Time Required: 
30 minutes, including discussion
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: 
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
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: 

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