Extended structure

27 Jun 2019

Porphyrin-Based Metal-Organic Frameworks

Submitted by Amanda Bowman, Colorado College
Evaluation 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.

Corequisites: 
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
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.

 

8 Jun 2019

VIPEr Fellows 2019 Workshop Favorites

Submitted by Barbara Reisner, James Madison University

During our first fellows workshop, the first cohort of VIPEr fellows pulled together learning objects that they've used and liked or want to try the next time they teach their inorganic courses.

12 Dec 2018

Foundations Inorganic Chemistry for New Faculty

Submitted by Chip Nataro, Lafayette College

What is a foundations inorganic course? Here is a great description

https://pubs.acs.org/doi/abs/10.1021/ed500624t

 

Prerequisites: 
Corequisites: 
Course Level: 
15 Jun 2018
Evaluation Methods: 

I typically evaluate this activity through class participation although the answer key is posted after class to let the students evaluate their own understanding of concepts.  The students do know that they will be tested on the material within the activity and usually I have a density problem on the exam.

Evaluation Results: 

This activity is designed to give the students more freedom as they move from the first density calculation to the last set of calculations.  Within the last set of calculations, they encounter a hexagonal unit cell so that may require some additional intervention to get them to think about how to calculate the volume of a hexagonal unit cell.

Description: 

This activity is designed to relate solid-state structures to the density of materials and then provide a real world example where density is used to design a new method to explore nanotoxicity in human health.  Students can learn how to calculate the density of different materials (gold, cerium oxide, and zinc oxide) using basic principles of solid state chemistry and then compare it to the centrifugation method that was developed to evaluate nanoparticle dose rate and agglomeration in solution.

 

Learning Goals: 

A student should be able to calculate a unit cell volume from structural information, determine the mass of one unit cell, and combine these two parameters to calculate the density for both cubic and hexagonal structures.  In addition, students will have an opportunity to read a scientific article and summarize the major findings, place data in a table, and explain the similarities and differences between the densities calculated in the activity and the experimental values that are reported in the literature.

Corequisites: 
Course Level: 
Equipment needs: 

None

Prerequisites: 
Implementation Notes: 

I have used this activity in our first semester inorganic chemistry course when we cover solid-state materials.  One thing to note is that I do use 2-D projections to describe structures and we cover that in a previous activity.  You could remove 2-D projections from this activity if it is not something that you previously covered.  

 

Time Required: 
This activity usually takes about 40 to 45 minutes.

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