# Electronic spectroscopy

10 Aug 2015

## A Demonstration to Segue Between d to d and CT Transitions

Submitted by Marion E. Cass, Carleton College
Evaluation Results:

Students easily associate intensity of color with the concentration of a solute from their work in previous general chemistry and analytical chemistry courses.  My goal in this exercise is to have them learn that the magnitude of the molar extinction coefficient is a measure of the intensity of the absorption and a function of the quantum mechanical allowedness of the transition. Physically observing the relative intensity of three solutions of the same concentration forces them to struggle with the concept of intensity of an absorption in contrast to the concept of the color that results from the energy of that absorption(s).  In the faculty only files I have included an exam question I have given to evaluate student comprehension of this concept.  This is a question I aspire for 100% perfect scores, however my data show that 3 students in a class of 15 (so around 20%) did not get a perfect score on this problem.

Description:

The following is a simple in-class “demonstration” that I use to segue between d to d and charge transfer transitions.  After teaching about d to d transitions and Tanabe-Sugano Diagrams, I show my students three solutions that I have put in large test tubes before class. The three solutions I place in the test tubes are:

a.  10 ml of 0.1M Co(H2O)62+

b.  10 ml of 0.1M Cu(H2O)62+

c.  10 ml of a freshly prepared 0.1 M KMnO4 solution

We review what we have learned about using Tanabe Sugano diagrams to predict the maximum number of possible d to d transitions that could  be observed for a given metal ion (with a given oxidation state, d electron configuration, and proposed high or low spin state) in the visible spectrum that give rise to color.

We then use observations of the KMnO4 solution to segue to the discussion of a different type of electronic transition: Charge Transfer.

I have also included an exam question that could be used to evaluate student understanding of the concept highlighted in the demonstration.

Learning Goals:

Demonstration to Segue Between d to d and CT Transitions

Learning Objectives:  Going into this exercise:

1.  Students should be able to determine the oxidation state and d electron count for a given set of metal complexes.

2.  Students should be able to propose whether a metal complex should be high or low spin (or state whether high and/or low spin are irrelevant designations) for a given metal d electron configuration.

3.  If they have learned about Tanabe-Sugano diagrams, students should be able to propose the maximum number of d à d transitions that could be observed for a given metal ion with a given d electron configuration and a given LS or HS designation.

3.  Students should be able to visually compare three solutions of different metal complexes with the same concentration and recognize that they vary in color as well as intensity.

Following the Demonstration:

Students should be open minded and prepared to learn about why many transition metal complexes have the beautiful and intense colors that they do (over and beyond the color imparted by d to d transitions that fall in the visible).

Course Level:
Topics Covered:
Corequisites:
Time Required:
20 minutes to prepare the demonstration, 10 minutes in class before beginning a section on CT transitions
2 Jul 2015

## Peer Review - How does it work?: A literature discussion with a focus on scientific communication

Submitted by Michael Norris, University of Washington
Evaluation Methods:

Students can hand in tthe first set of questions as homework which may be evaluated.  Class participation and group work may also be graded appropriately.

Evaluation Results:

This is an untested LO.

Description:

This learning object is based on discussion of the literature, but it follows a paper through the peer review process.  Students first read the original submitted draft of a paper to ChemComm that looks at photochemical reduction of methyl viologen using CdSe quantum dots.  There are several important themes relating to solar energy storage and the techniques discussed, UV/vis, SEM, TEM, electrochemistry, and catalysis, can be used for students in inorganic chemistry.

Unlike a typical literature LO where students discuss only the current science, this LO contains the actual reviewer comments to the original submitted manuscript as well as a link to the final version that was published in Journal of Materials Chemistry A.

DOI: 10.1039/C5TA03910J

Prerequisites:
Course Level:
Learning Goals:

Students will be able to...

·  Communicate the main ideas of a scientific research paper to classmates.

·  Identify the research area, importance of the research, and background information provided in a scientific paper.

·  Discuss areas of a paper that may be improved through revision.

·  Compare their views of necessary revisions with actual anonymous reviewers on a scientific paper and the eventual publication.

·  Understand the importance and shortcomings of the peer review process using an actual publication from the literature.

Implementation Notes:

The LO has multiple sections which may be discarded or edited depending on the particular learning goals desired.  While the chemistry may be difficult for lower level students, the discussion of the peer review process may be valuable to students across multiple levels and even in writing courses.  Also provided are the authors' actual responses to the reviewers comments.  It should also be noted that the original article was submitted to ChemComm, but the subsequent revised article was submitted and accepted to Journal of Materials Chemistry A.

Time Required:
Homework Assignment + 1 h in class
29 Jun 2015

## Teaching and Learning Package Library from University of Cambridge

Submitted by Vanessa McCaffrey, Albion College
Evaluation Methods:

I required students to come to class with written questions about the material. This is graded as credit/no credit. If they don't have any questions, they are then required to answer the class questions. This usually encourages complete participation.

Evaluation Results:

Student reported in the end of semester evaluations that they liked the online tutorials better than the book, especially with the semiconductor section.

Description:

This is a resource that has short, animated tutorials on a variety of different topics. Most of the topics are materials science and/or engineering topics but there are several that would be of interest to chemistry students. (A full list of topics is given below.)

I have used "An Introduction to Semiconductors", "Crystallography" and "Lattice Planes and Miller Indices" in my classes. These were used as reading assignments and didn't have formal assessments associated with them, mostly because I found them too late to get anything together! Assessments and homework assignments associated with these tutorials are being developed and will be posted.

Chemistry topics include:

More Engineering topics (any mistakes in sorting are my own!):

Corequisites:
Prerequisites:
Course Level:
Learning Goals:

After working through one or more of the tutorials, students should be able to:

- well, it depends on the tutorial. The nice thing about these is that under the "Aims" tab, each tutorial has a very specific list of Learning Goals.

- Gain an appreciation for the techniques and concepts in materials science and chemistry!

Related activities:
Implementation Notes:

I have used several of the tutorials in my class as reading assignments. We generally come back to class the next day and work through each of the slides in order. I have usually left out any of the quantitative slides, focusing mostly on the qualitative concepts.

Once the questions are answered, we move as a class to the Questions tab. As a class, we then work through as many of the problems as we can in the "Questions" setion.

I haven't done much more than that with my classes, but plan on developing HW sets or exam questions to make sure that students are taking something from the tutorials.

Time Required:
30 - 50 minutes per tutorial
10 Jun 2015

## Education Resources at Beloit College - Materials Chemistry, Nanoscience and Solid State Chemistry

Submitted by Barbara Reisner, James Madison University
Description:

The resources on this website will help students learn concepts in materials chemistry, solid state chemistry, and nanoscience. The website provides links to

• a video lab manual,
• a cineplex of demonstrations,
• kits that can be used for extended structures, and
• interactive structures of solid state materials, Au nanoparticles and forms of carbon.

There videos and resources have applications across the chemistry curriculum. Many materials are inorganic. This is a great resource for people looking for ways to incorporate the new CPT guideline to discuss macromolecular, supramolecular, mesoscale and nanoscale systems within the framework of their existing curriculum.

Course Level:
Prerequisites:
Corequisites:
10 Jun 2015

## Web Resources from the 2013 Inorganic Curriculum Survey

Submitted by Barbara Reisner, James Madison University

In the 2013 Inorganic Curriculum Survey, respondents were asked about the resources they used when they teach inorganic chemistry. About 20% of respondents selected "other" and provided information about these resources. A number of people mentioned specific websites. This collection consists of the websites submitted in the survey.

Prerequisites:
Corequisites:
Course Level:
24 Apr 2015

## Tanabe Sugano Diagram JAVA Applets

Submitted by Amanda Reig, Ursinus College
Description:

A series of JAVA applets of Tanbe-Sugano diagrams were developed by Prof. Robert Lancashire at the University of the West Indies.  These diagrams allow students to determine deltao/B values based on ratios of peak energies without the pain of rulers and drawing lines.  There are also features that allow a person to input values and automatically calculate certain parameters.  You can also quickly find values of delta_o and B for certain complexes via a drop-down menu on some of the pages (e.g. Cr3+ complexes).

Course Level:
Topics Covered:
Prerequisites:
Learning Goals:

Students will be able to interpret absorption spectra using the provided Tanabe-Sugano diagram applets.

Subdiscipline:
Related activities:
Implementation Notes:

I use these applets when teaching Tanabe-Sugano diagrams in my class and students get significant practice with the applets through homework assignments and a lab experiment.

Note that you cannot use Chrome (Firefox or Internet Explorer both work) and you will likely need to add the website to your "safe" list in your JAVA settings in order for the applets to work.

8 Mar 2015

## Community Challenge #2: Symmetry and MO Theory

Submitted by Nancy Scott Burke Williams, Scripps College, Pitzer College, Claremont McKenna College
Course Level:
Corequisites:
Prerequisites:
5 Jan 2015

## The Color and Electronic Configurations of Prussian Blue

Submitted by Erica Gunn, Simmons College
Evaluation Methods:

Student answers to the reading comprehension questions were collected at the beginning of class and graded out of 10 points (largely based on participation and completeness of answers).

Evaluation Results:

Most students were able to identify the correct answers from the paper, though some were confused by the last section involving orbital calculations (this was expected, as most of these students have not yet had a course in quantum mechanics).

Some students also had difficulty following the logic presented in the paper to predict differences in absorption band intensity for the different Fe compounds. Most recognized that the absorption band position was important and some realized that intensity also mattered, but most did not fully follow the arguments for assigning absorption spectra to one particular complex geometry. Most of the class discussion involved recreating the logic behind the peak assignment for the absorption spectra.

Description:

I used this paper to illustrate several course concepts related to materials structure (crystal lattice structure, coordination number, crystal field theory and orbital splitting, symmetry, electronic spectra, allowed and forbidden transitions). This activity was paired with a laboratory experiment (see related VIPEr objects) in which students synthesized Prussian Blue, and gave students a really in-depth look at what was going on when they mixed those solutions together. Combined with another VIPEr activity that uses a more recent literature example (New Blue Solid, in related links), students gained a broad appreciation for how inorganic chemists can use these concepts to rationally design new materials.

Corequisites:
Prerequisites:
Course Level:
Learning Goals:

Become familiar with reading chemical literature

Use symmetry and electronic configuration to interpret absorption spectra

Integrate understanding of course concepts to understand a "real life" literature example and enhance student interest

Implementation Notes:

These activities were used in a 200-level course, which happened to mostly populated by juniors and seniors. The reading questions were designed mainly to check for basic comprehension. Most students had no difficulty answering the "what" questions about the experiments done and facts presented, but many needed significant guidance to understand why the researchers made these particular measurements, and how they interpreted the data to arrive at the conclusions presented. Most of the class discussion focused on building a "big picture" overview of what was going on. This led to interesting questions about design of experiments and use of evidence in science. Several students were surprised at how much of the scientific argument they had missed in their first reading of the paper, even though they felt like they had a good grasp on the data that the authors had reported.

Time Required:
1 hour
23 Sep 2014

## Five Slides about Spectroelectrochemistry (SEC)

Submitted by Kyle Grice, DePaul University
Description:

This "Five slides about" is meant to introduce faculty and/or students to Spectroelectrochemistry (SEC), a technique that is used in inorganic chemistry research and other areas. SEC is a powerful tool to examine species that are normally hard to synthesize and isolate due to instability and high reactivity. Papers with examples of SEC techniques are provided on the last slide.

Corequisites:
Course Level:
Learning Goals:

Students should be able to describe spectroelectrochemistry

Students should be able to conceptually explain how a spectroelectrochemical cell works

Students should be able to explain the benefits of spectroelectrochemistry as compared to standard synthesis and spectroscopy approches

Related activities:
Implementation Notes:

Ideally, the students would take this introduction and then go and examine specific instances of SEC in the literature. Alternatively, this can be used to help explain research papers that are being discussed that use SEC techniques.

Students should already have an understanding of the basics of electrochemistry and spectroscopy prior to learning SEC, so this would be best suited for an upper division, special topics course in Inorganic Chemistry or Spectroscopy. There are some nice LO's on these techniques already on Ionic Viper (see related activities).

There are some good images of the specifics of SEC cell designs on company websites or journal articles (the Organometallics article shown in the web resources is one such article).

IR-SEC is included in the paper that is the focus of the "Dissection Catalysts for Artificial Photosynthesis" LO.

Time Required:
15 min
Evaluation
Evaluation Methods:

This LO was made as a followup to the 2014 Ionic Viper workshop and has not been implemented yet. However, I plan on implementing it in a "Special Topics in Inorganic Chemisry" course in the future.

Evaluation Results:

None yet, will be provided upon implementation.

15 Sep 2014

## Fe2GeS4 Nanocrystals for Photovoltaics

Submitted by Anne Bentley, Lewis & Clark College
Evaluation Methods:

My student led a 20-minute class discussion of this article in the spring of 2014.  The other students in the class were asked to post two questions about the article to moodle before the class meeting, but they were not asked to complete the literature discussion questions due to assignment overload at the end of the semester.

Evaluation Results:

The six students posted good questions about the article, some of which I have incorporated into the literature discussion. One student asked why Ge was used instead of Si.  (My guess is that Si is too prone to oxidation - it's consistent with redox potentials.)  Another student wanted to know if any articles had been published after this one describing further progress.  At least two asked how the authors could determine that the photocurrent was p-type.

Description:

I asked the students in my junior/senior inorganic course to develop their own literature discussion learning objects and lead the rest of the class in a discussion of their article.  Student Johann Maradiaga chose this article describing the synthesis and characterization of Fe2GeS4 nanocrystals with potential applications in photovoltaic devices (Sarah J. Fredrick and Amy L. Prieto, “Solution Synthesis and Reactivity of Colloidal Fe2GeS4: A Potential Candidate for Earth Abundant, Nanostructured Photovoltaics” J. Am. Chem. Soc. 2013, 135, 18256-18259. DOI: 10.1021/ja408333y).  The article describes the synthesis in hexadecylamine/octadecene of Fe2GeS4 nanoparticles and their characterization using powder X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, UV-vis spectroscopy, and photocurrent measurements.  Building on Johann’s original set of questions, I developed this literature discussion, which is suitable for use in inorganic chemistry courses. Many thanks to article author Sarah Fredrick for reviewing the assignment and adding some great questions.

Corequisites:
Prerequisites:
Course Level:
Learning Goals:

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

• Understand how variable growth rates along different crystal planes result in specific shapes, and predict a resulting shape given a particular set of growth rates
• Compare the oxidation behavior of Fe and Ge over time using XPS data
• Describe a photocurrent measurement experiment and compare the photocurrent behavior of p-type and n-type semiconductors.
• Explain the value of a communication as compared to a longer research article

Subdiscipline:
Implementation Notes:

Students do not need to be experts to understand this article, but previous exposure to solid state concepts including semiconductor electronic structure, solid state phases, nanoparticle synthesis, and capping agents will be helpful to them.  Alternatively, the article could be used to introduce these topics.

This JACS communication is fairly short and written clearly, so it could make a good first literature discussion for students without previous experience reading journal articles.

I have included a large number of possible questions in the literature assignment, but as always, users should feel free to pick and choose from the options and/or add their own.

Time Required:
45 minutes (approximately)