21
Jan
2020
General Chemistry
17
Jan
2020
Formal oxidation states in Ru-catalyzed water oxidation
Submitted by Margaret Scheuermann, Western Washington UniversityEvaluation Methods:
I did not grade this activity.
Evaluation Results:
Three students out of 14 explicitly mentioned that this activity was helpful on the free response section of the course evaluations.
Description:
This LO is an in-class assignment to prepare students for literature readings involving catalytic cycles in which multiple protons and electrons are transferred. Students practice assigning oxidation states to complexes with aquo, oxo, superoxo, and hydroperoxo ligands then use this information to analyze a proposed water oxidation mechanism from the literature.
Students are asked to add in the substrates and products entering and leaving the catalytic cycle. While this is, at its heart, a stoichiometry excercise, it helps calibrate students for the level of attention to detail needed to effectively engage with reading about multi-electron catalytic mechanisms.
Learning Goals:
After completing this activity:
A student should be able to assign formal oxidation states to monometallic complexes with aquo, oxo, hyrdoperoxo, and superoxo ligands
A student should be able to apply their knowledge of formal oxidation states to the analysis of a proposed mechanism of a catalytic water oxidation reaction
Corequisites:
Subdiscipline:
Prerequisites:
Course Level:
Related activities:
Implementation Notes:
I used this activity during a lab lecture before an inorganic laboratory experiment in which students would be preparing and testing the Ru-based OEC mimic.
I began the class period with a brief review of L/X type ligands and formal oxidation states.
Students then worked in groups to complete this activity.
Other implementation options:
While I used this activity as part of a lab lecture it could also be used in a lecture setting or as part of a problem set.
It could also be modified for use as an equation balancing excercise in a majors or honors general chemistry course.
Time Required:
10-20 minutes
Web Resources:
18
Oct
2019
Mechanisms of Mn-catalyzed water oxidation reactions
Submitted by Margaret Scheuermann, Western Washington UniversityEvaluation Methods:
I did not grade this activity.
Evaluation Results:
Three students out of 14 explicitly mentioned that this activity was helpful on the free response section of the course evaluations.
Description:
This LO is an in-class assignment to prepare students for literature readings involving catalytic cycles in which multiple protons and electrons are transferred. Two catalytic mechanisms, a proposed OEC mechanism and the proposed mechanism of a biomimetic OEC complexes are included. The intermediates are drawn including all charges and oxidation states, details which are sometimes omitted in the primary literature but can be helpful to students who are not accustomed to looking at multistep catalytic cycles. Students are then asked to add in the substrates and products entering and leaving the catalytic cycle. While this is, at its heart, a stoichiometry excercise, it helps calibrate students for the level of attention to detail needed to effectively engage with reading about bioinorganic catalytic mechanisms.
Learning Goals:
After completing this activity:
A student will be able to follow along with each step in proposed water oxidation mechanims in the literature.
A student will be able to apply their knowledge of stoichiomety to complex catalytic cycles involving electron transfer.
A student will be able to analyze and compare the details of catalytic cycles.
Corequisites:
Subdiscipline:
Prerequisites:
Topics Covered:
Course Level:
Related activities:
Implementation Notes:
I used this activity during a lab lecture before an inorganic laboratory experiment in which students would be preparing and testing an OEC mimic. The procedure we used was roughly based on a published procedure (J. Chem Ed. 2005, 82, 791) linked in web resources.
I began the class period with a brief introduction to the chemistry of photosynthesis and where water oxidation and PSII fit in the broader picture. I then introduced the mimic that students would be preparing and the chemistry of the Oxone (R) triple salt.
Students then worked in groups to complete this activity and discuss their structural and mechanistic observations. After the activity they were encouraged to read the papers referenced in the activity and to think about the evidence that supports the proposed mechanism.
Other implementation options:
While I used this activity as part of a lab lecture it could also be used to stimulate a discussion comparing structure/mechanism of biological and biomimetic systems in a lecture setting without the accompaning laboratory work.
This could also be modified for use as an equation balancing excercise in a majors or honors general chemistry course.
Time Required:
10-20 minutes
Web Resources:
8
Oct
2019
1FLO: Post-Synthetic Modifications for Tunneling Electrical Connection to the Interior of Metal-Organic Frameworks
Submitted by daniel kissel, Lewis UniversityEvaluation Methods:
assessment of students will be preformed by grading their answers to the questions in the activity.
Description:
This is a 1 Figure lit discussion (1FLO) based on a Figure from a 2015 JACS article on synthesizing conductive MOFs. This LO introduces students to Metal-Organic Frameworks and focuses on characterization techniques and spectroscopy.
Prerequisites:
Corequisites:
Topics Covered:
Course Level:
Learning Goals:
As a result of completing this activity, students will be able to...
- define what metal-organic Frameworks and Post-synthetic Modifications are
- understand MOF terminology and notation
- discover how mass transport and electron mobility effect conductivity
- calculate energies of electronic transitions in electron volts
- make connections betweeen diagrams and material sturctures
- compare optical and microscopy techniques
- discover the concept of photocurrect and how it could be used in different applications
Subdiscipline:
Related activities:
Implementation Notes:
Students should be able to complete the activity without any prior knowledge of MOFs, although some introduction to MOFs and UV-vis absorption spectroscopy would be nice.
29
Jul
2019
Introduction to Drago's ECW Acid-Base Model
Submitted by Colleen Partigianoni, Ferris State UniversityDescription:
This LO was created to introduce Drago’s ECW model, which is an important contribution to the discussion of Lewis acid-base interactions. Unlike the qualitative Pearson’s HSAB model (Hard Soft Acid-Base model,) the quantitative ECW model can be used to correlate and predict the enthalpies of adduct formation and to obtain enthalpy changes for displacement or exchange reactions involving many Lewis acids and bases. Unlike all other acid-base models, graphical displays of the ECW model clearly show that there is no one order of acid or base strengths, and illustrate that two parameters are needed for each acid and base to provide an order of acid or base strength. The ECW model can also provide a measure of steric strain energy or pi bonding stabilization energy accompanying adduct formation, which is not possible with any other acid-base model.
This set of slides is intended to provide a basic introduction to the model and several examples of predicting energy changes using the model. It also illustrates how to construct and interpret a graphical display of the model.
It should be noted that this LO is not in the PowerPoint format, but instead is a more extensive set of notes for instructors who are not familiar with the ECW model. It could be condensed and rewritten in the more standard PowerPoint format.
There is also an ECW problem set LO that can used to supplement this LO.
Prerequisites:
Subdiscipline:
Topics Covered:
Course Level:
Corequisites:
Learning Goals:
After viewing the slides, students, when provided with appropriate data, should be able to:
- Calculate sigma bond strength in Lewis acid-base adducts using Drago’s ECW model.
- Show how to deal with any constant energy contribution (W) to the reaction of a particular acid (or base) that is independent of the base (or acid) when an adduct is formed.
- Garner information regarding steric effects and pi bond stabilization energy in Lewis acid-base adducts using the ECW model.
- Show using a graphic display of ECW that two parameters for each acid and each base are needed in acid-base models to determine relative strengths of donors and acceptors.
Web Resources:
25
Jul
2019
1FLO: One Figure Learning Objects
Submitted by Chip Nataro, Lafayette CollegeCourse Level:
Subdiscipline:
Topics Covered:
Corequisites:
Prerequisites:
27
Jun
2019
Porphyrin-Based Metal-Organic Frameworks
Submitted by Amanda Bowman, Colorado CollegeEvaluation Methods:
Students completed this activity in small groups, then turned in individual worksheets. Student learning and performance were assessed through 1) in-class group discussion after they had worked on the activity in small groups, and 2) grading the individual worksheets. Participation was most important in the small-group portion.
Evaluation Results:
In general, students really enjoyed this exercise and felt that it was helpful for visualizing metal-organic frameworks (particularly the extended 3D structure). They also generally felt that it was helpful in visualizing the bonding sites of metal vertices, particularly for thinking about how that influences potential reactivity. We used Mercury as a visualization software for this discussion, and the majority of students felt very comfortable using Mercury and looking at cifs on their own after this activity.
The biggest challenge for students seemed to be in relating the 3D structure in the cif to the images and chemicals formulas in the article. They also tended to need some hints about question 5 – to think about what information Mössbauer can provide about oxidation state of the metal, or that you can tell whether or not there are two distinct iron environments. In our class, we do brief units on X-ray crystallography including how to use and interpret cifs, and Mössbauer spectroscopy before this literature discussion. If those topics are not already addressed in a particular class it might be helpful to add them in or directly address those topics for the students as an introduction to the literature discussion.
Description:
This literature discussion explores the physical structures, electronic structures, and spectroscopic characterization of several porphyrin-based metal-organic frameworks through discussion of “Iron and Porphyrin Metal−Organic Frameworks: Insight into Structural Diversity, Stability, and Porosity,” Fateeva et al. Cryst. Growth Des. 2015, 15, 1819-1826, http://dx.doi.org/doi:10.1021/cg501855k. The activity gives students experience visualizing and interpreting MOF structures, and gives students exposure to some of the methods used to characterize MOFs.
Prerequisites:
Corequisites:
Topics Covered:
Course Level:
Learning Goals:
Students will be able to:
- Interpret and describe the bonding and structural characteristics of MOFs
- Apply knowledge of ligand field strength to electronic structure of MOFs
- Analyze X-ray crystallographic data to gain information about structural characteristics of MOFs
- Interpret Mössbauer spectra to gain information about electronic structure of MOFs
Subdiscipline:
Related activities:
Implementation Notes:
This literature discussion was designed for use in an advanced (upper-level) inorganic chemistry course, but could be used in a foundational inorganic course if students have already been introduced to d-splitting diagrams and are given some coverage of Mössbauer spectroscopy and X-ray crystallography. When covering MOFs in class, students frequently expressed that visualizing and understanding the bonding sites and extended 3D structures was very challenging. So, this literature discussion was developed specifically to address that. Students completed this activity in small groups. It is very helpful to advise students ahead of time to bring laptops (or instructor should have some available) and to have the cifs from the paper downloaded and ready to go. We used Mercury as a visualization software for this activity. This activity can easily be completed in one class period. It is also helpful if students have been provided with the article ahead of time and encouraged to look it over – otherwise the most time-consuming part of this activity was allowing time for students to examine the MOF structure images in the paper before being able to discuss and answer the questions with their groups.
Note on visualization of MOFs using Mercury: To answer the discussion questions, we used the ‘stick’ or the ‘ball and stick’ style. We also used the default packing scheme (0.4x0.4x0.4) and the 1x1x1 packing scheme. The packing scheme can be changed by selecting Packing/Slicing… in the Calculate menu. I also had students view the 3x3x3 packing scheme – while this is not necessary to answer the discussion questions, it was interesting for students to be able to visualize the extended structure of the MOFs.
Web Resources:
9
Jun
2019
Inorganic Chemistry
Submitted by Caroline Saouma, University of Utah
9
Jun
2019
1FLO: PCET and Pourbaix
Submitted by Anne Bentley, Lewis & Clark CollegeEvaluation Methods:
I graded each student’s problems as I would any other homework assignment, and they averaged about 80% on that part of the assignment. The other half of the total points for the assignment came from in-class participation.
Evaluation Results:
We had a rich conversation about this article in class; it was probably one of the most interesting literature discussion conversations I’ve had. Although this was the only introduction to Pourbaix diagrams in the course, 12 of 15 students correctly interpreted a “standard” Pourbaix diagram on a course assessment.
Description:
This set of questions is based on a single figure from Rountree et al. Inorg. Chem. 2019, 58, 6647. In this article (“Decoding Proton-Coupled Electron Transfer with Potential-pKa Diagrams”), Jillian Dempsey’s group from the University of North Carolina examined the mechanism by which a nickel-containing catalyst brings about the reduction of H+ to form H2 in non-aqueous solvent. Figure 3 in the article presents an excellent introduction to the use of Pourbaix diagrams and cyclic voltammetry to determine the mechanism of a proton-coupled electron transfer reaction central to the production of hydrogen by a nickel-containing catalyst.
Prerequisites:
Corequisites:
Topics Covered:
Course Level:
Learning Goals:
Students should be able to:
- identify atoms in a multidentate ligand that can coordinate to a metal as a Lewis base
- outline the difference between hydride addition to a metal and protonation of a ligand in terms of changes to the overall charge of the complex
- analyze a Pourbaix diagram to predict the redox potential and pKa of a species
Subdiscipline:
Related activities:
Implementation Notes:
I have discussed the challenge of integrating literature discussions into my inorganic course in a BITeS post and the VIPEr forums. Each spring I try something a little different. This year I used three articles from the literature to frame our review of course material at the end of the semester, with each literature discussion occupying a one-hour class meeting.
In each case, the students completed problems before coming to class. While these problems were based on the journal articles, they did not require the students to read / consult the journal articles in order to complete the assignment. The students brought an electronic or paper copy of the article to class. I usually put students in groups (approximately 3 per group) and gave each group new questions to work on, which did draw from the article. After some time working in groups, each group presented their material to the rest of the class.
In implementing this particular literature discussion, I didn’t have any further questions for them. I walked through some of the other figures from the article (especially Figure 1). We discussed the authors’ use of color in creating Figure 3. We also reviewed the significance of horizontal vs vertical vs diagonal lines. Because I had not covered Pourbaix diagrams in the course, the activity was a good introduction to the concept.
Because these problems don’t require consultation with the article, they are suitable to use on an exam.
Time Required:
varies
9
Jun
2019
Intermediate Inorganic Chemistry, Spring 2020
Submitted by Jason S. D'Acchioli, University of Wisconsin-Stevens PointPages
