Electronic spectroscopy

3 Jun 2017

Literature Discussion of R3CH→ SiFR3 Agostic Interactions

Submitted by Tanya Gupta, South Dakota State University
Evaluation Methods: 

Some discussions questions can be taken out and used for exams, quizzes or problem sets.

The instructor can develop a rubric to evaluate these questions based on their needs.

Evaluation Results: 

Monitoring student discussions, or grading student written responses based on implementation.

Description: 

The set of questions in this literature discussion activity is intended to engage students in reading and interpreting scientific literature and to develop a clear and coherent understanding of agostic interactions. The activity is based on a paper by Dorsey & Gabbai (2008). The paper describes agostic interactions in a silicon-based compound (R3C-H→SiFR3). The set of questions in this literature discussion activity is appropriate for an upper division course in inorganic chemistry. The research described in the article ties together concepts of agostic interactions and their impact on the coordination geometry of a Lewis acidic species. The discussion activity includes guided questions for students to understand and determine the presence of agostic interactions experimentally and through computational methods. The activity has specific questions related to bonding, structure, synthesis, characterization, theoretical and computational methods used in the literature. The activity may require reviewing some secondary sources.

Corequisites: 
Course Level: 
Learning Goals: 

Students will be able to..

  • Define an agostic interaction and relate it to other types of bonding.

  • Describe how the agostic interaction affects the coordination geometry of a Lewis acidic atom.

  • Provide examples of how the presence of an agostic interaction can be determined experimentally and through computational methods.

  • Differentiate between computational methods in terms of the information they can provide.

  • Find related sources of information to aid in comprehension of the concepts in the article.

 

Implementation Notes: 

This literature discussion was developed at the VIPEr 2017 workshop at Franklin and Marshall College so it has not yet been implemented. The authors believed that implementation of this article is best for an inorganic course that is post-organic, post-spectroscopy. It could be helpful after a discussion of 3-center 2-electron bonding and/or Lewis acidity/basicity. As with all lit. discussion LOs, this article also provides a valuable experience in reading the literature, including an interpretation and analysis of the experimental section. There are many questions included in this activity and instructors may want to pick and choose these questions and adapt it to their class.

Time Required: 
1 class (50 minutes)
3 Jun 2017

An ion exchange method to produce metastable wurtzite metal sulfide nanocrystals

Submitted by Janet Schrenk, University of Massachusetts Lowell
Evaluation Methods: 

Evaluation methods are at the discretion of the instructor. For example, you may ask students to provide written answers to the questions, evaluate whether they participated in class discussion, or ask students to present their answers to specific questions to the class.

Description: 

In this literature discussion, students use a paper from the literature to explore the synthesis, structure, characterization (powder XRD, EDS and TEM) and energetics associated with the production of a metastable wurtzite CoS phase. Students also are asked define key terms and acronyms used in the paper; identify the goal of the experiments and determine if the authors met their goal. They examine the fundamental concepts around the key crystal structures available.  

 

Preserving Both Anion and Cation Sublattice Features during a Nanocrystal Cation-Exchange Reaction: Synthesis of a Metastable Wurtzite-Type CoS and MnS

Powell, A.E., Hodges J.M., Schaak, R.E. J. Am. Chem. Soc. 2016, 138, 471-474.

http://pubs.acs.org/doi/abs/10.1021/jacs.5b10624

 

There is an in class activitiy specifically written for this paper. 

Corequisites: 
Learning Goals: 

In answering these questions, a student will be able to…

  • define important scientific terms and acronyms associated with the paper;

  • describe the rocksalt, NiAs, wurtzite, and zinc blende in terms of anion packing and cation coordination;

  • differentiate between the structure types described in the paper;

  • explain the difference between thermodynamically stable and metastable phases and relate it to a free energy diagram; and

  • describe the structural and composition information obtained from EDS, powder XRD, and TEM experiments.

Prerequisites: 
Implementation Notes: 

This learning object was created at the 2017 IONiC Workshop on VIPEr and Literature Discussion. It has not yet been used in class.

Time Required: 
50 minutes
3 Jun 2017

Quantum Dot Growth Mechanisms

Submitted by Chi Nguyen, United States Military Academy
Evaluation Methods: 

The question document attempted by students in preparation for the literature discussion will be due prior to the in-class discussion. In particular, students' performance on the particle-in-a-box question will be evaluated to assess retention from the previously covered course material. The next exam following the discussion will contain specific question(s) (data/figure analysis) addressing these topics. Students' performance difference between the two will be evaluated. The extent to which students improve their post-discussion understanding of the concepts will direct future implementation.

Evaluation Results: 

To be determined. This is a newly proposed literature discussion.

Description: 

This literature article covers a range of topics introduced in a sophomore level course (confinement/particle-in-a-box, spectroscopy, kinetics, mechanism) and would serve as a an end-of-course integrated activity, or as a review activity in an upper level course. The authors of the article employ UV-vis absorption spectroscopy of CdSe quantum dots as a tool to probe the growth mechanism of the nanoparticles, contrasting two pathways.

 

Reference:  DOI 10.1021/ja3079576 J. Am. Chem. Soc. 2012, 134, 17298-17305

 
Corequisites: 
Prerequisites: 
Learning Goals: 

Apply the particle in a box model to interpret absorbance spectra with respect to nanoparticle size.

 

Analyze the step-growth and living chain-growth mechanisms proposed in this paper.

 

Evaluate the kinetics as it applies to the step-addition.

 

Recognize and apply multiple scientific concepts in an integrative manner.
Implementation Notes: 

Sophomore level implementation:  Recommend focusing on select portions (e.g. Figures 1b, 2, 5 with corresponding text) of the paper rather than having students read the entire document.  The learning objects focus on select topics, such as particle-in-a-box, reaction mechanism, and kinetics in conjunction with absorbance spectroscopy.  This would be a good literature discussion resource for an end-of-course integrative experience that encompasses multiple topics from general chemistry and inorganic chemistry.  

 

Advance level implementation:  For an upper division course, incorporate the paper in its entirety early in the course as an assessment on students’ ability to integrate multiple concepts that they should have learned in general chemistry, organic chemistry, and physical chemistry.  To enhance the experience, accompanying the literature discussion on this paper with a laboratory experience by repeating the experimental and characterization procedures presented in the paper, and having students' compare their results with published results.  This also serves to enhance students’ scientific literacy by critically assessing the quality of the paper.

 

Excerpts of the paper and questions can be used on a graded event, or as lesson preparation for in class discussion.

 
Time Required: 
In-class discussion takes approximately 50 minutes with students having already read the paper and submitted their responses to the questions.
4 Jan 2017
Description: 

This is a great new textbook by George Luther III from the University of Delaware.  The textbook represents the results of a course he has taught for graduate students in chemical oceanography, geochemistry and related disciplines.  It is clear that the point of the book is to provide students with the core material from inorganic chemistry that they will  need to explain inorganic processes in the environment.  However the material is presented in such a clear, logical fashion and builds so directly on fundamental principles of physical inorganic chemistry that the book is actually applicable to a much broader audience.  It provides a very welcome presentation of frontier orbital theory as a guide to predicting and explaining much inorganic chemical reactivity.  There are numerous very  helpful charts and tables and diagrams.  I found myself using the book for a table of effective nuclear charges when I was teaching general chemistry last semester.  The examples are much more interesting that the typical textbook examples and would be easy to embellish and structure a course around.  There is also a helpful companion website that provides powerpoint slides, student exercises and answers.  The book covers some topics not typically seen in inorganic textbooks like the acidity of solids but the presentation of this information makes sense in light of the coherent framework of the text.  We so often tell our students "structure dictates function".  This text really make good on that promise.  My only complaint is that I wish the title were something more generic so that I could use it for a second semester of introductory-esque material that we teach after students have taken a single semester of intro chem and two semesters of organic chemistry.  So much of what is covered in this textbook is precisely what a second semester sophomore chemistry major should know before proceeding on in the major.  But the title makes the book hard to sell to chemistry majors and that is regrettable. 

Prerequisites: 
Course Level: 
28 Dec 2016

Virtual Issue of Organometallics

Submitted by Chip Nataro, Lafayette College
Subdiscipline: 
Prerequisites: 
Corequisites: 
Course Level: 
30 Jun 2016

Basics of Lanthanide-Based Photophysics

Submitted by Jacob Charles Lutter, University of Michigan
Description: 

This 5 slides about outlines the basics of lanthanide photophysics as a primer for those new to the topic.  These properties are very unique and actually very useful, which is a topic for another time.  The intricacies of what causes the Ln luminescence, its strengths and drawbacks are discussed along with how these drawbacks are addressed in molecular complexes.  Notes for the instructor are included that explain each slide.

Prerequisites: 
Course Level: 
Subdiscipline: 
Learning Goals: 

Students should be able to explain the Laporte selection rule, and why it is so important to the Ln photophysical properties of absorption/excitation and lifetimes.

Students should be able to explain how the intrinsic nature of the 4f orbitals creates advantages and disadvantages for luminesecence.

Students should be able to design possible antenna ligands based on desired characteristics.

Implementation Notes: 

Feel free to use all or part of this presentation as you see fit. 

14 May 2016

Crystal Field Theory and Gems--Guided Inquiry

Submitted by Adam R. Johnson, Harvey Mudd College
Evaluation Methods: 

The 2 worksheets were handed in and graded according to the key. I generally used a +, √, - grading scale for the probelms. I gave a single grade for each group. Answer keys are provided as "faculty only" files.

Evaluation Results: 

The day 1 activities were too long and we didn't get to the square planar CFT derivation. For my next offering, I am adding a day to the unit so the students will see all three geometries. Students struggled a bit at first with the software and visualization but were able to figure it out with some assistance. The students in Fall 2015 had already practiced using Crystalmaker in a prior unit; for 2016, this prior unit has been removed so the visualization will probably take more time. I anticipate using 1.5 days for part 1 and 1.5 days for part 2 in Fall 2016.

Description: 

The colors of transition metal compounds are highly variable. Aqueous solutions of nickel are green, of copper are blue, and of vanadium can range from yellow to blue to green to violet. What is the origin of these colors? A simple geometrical model known as crystal field theory can be used to differentiate the 5 d orbitals in energy. When an electron in a low-lying orbital interacts with visible light, the electron can be promoted to a higher-lying orbital with the absorption of a photon. Our brains perceive this as color. Rubies, dark red, and emeralds, brilliant green, are precious gemstones known since antiquity. What causes the color in these beautiful crystals? Using crystal field theory, we can explain the colors in these gemstones.

Learning Goals: 

1.    Derive the crystal field splitting for d orbitals in an octahedral geometry
2.    Predict the magnitude of d orbital splitting
3.    Relate color, energy, wavelength, and crystal field strength
 

Equipment needs: 

Day 1: none

Day 2: access to laptops (one per group or individual) and crystalmaker software (free download avaialbe)

Corequisites: 
Course Level: 
Prerequisites: 
Implementation Notes: 

This LO was used in a first-year chemistry class at Harvey Mudd College in Fall 2015. I started with a brief lecture (see instructor notes) and then turned the class loose in small groups of about 5 students. I walked through the room to answer questions and guide the groups.

The first day’s activities were taken from a J. Chem. Educ. article (J. Chem. Educ., 2015, 92, 1369-1372). This article has a lot of detail that could be adapted for local use. The related activity "metal and Ionic Lattices Guided Inquiry Worksheet" may be appropriate as review/background material, depending on the placement of this activity in your syllabus.

The second day’s activities rely on the use of crystalmaker, a structure visualization program. There is a free demo version available (http://crystalmaker.com/software/index.html)

Fairly detailed instructor notes are included as a "faculty only" file.

The references for the structures I used are here:

Gibbs G V, Breck D W, Meagher E P (1968)  Structural refinement of hydrous and anhydrous synthetic beryl, Al2(Be3Si6)O18 and emerald, Al1.9Cr0.1(Be3Si6)O18 Note: hydrous emerald. Lithos 1:275-285

Wang X, Hubbard C, Alexander K, Becher P (1994)  Neutron diffraction measurements of the residual stresses in Al2O3 - ZrO2 (CeO2) ceramic composites _cod_database_code 1000059. Journal of the American Ceramic Society 77:1569-1575

I relied on a book called "The science of Color" and a website on color theory (linked below) to develop the 2nd days activities.

The Science of Color,” volume 2, edited by Alex Byrne and David R. Hilbert, MIT Press, Cambridge MA, 1997, pp. 10-17.

Time Required: 
2 50 minute class periods
15 Mar 2016

ColourLex - a colorful website!

Submitted by Vanessa McCaffrey, Albion College
Evaluation Methods: 

N/A

Evaluation Results: 

Students seem to like the examples that this website has.

Description: 

ColourLex (colourlex.com) is an amazing website that mixes chemistry and art. The creators of this website have extensively catalogued paintings and the pigments that were used to create them. The pigments range from artificial to natural and organic to inorganic. You can search for the specific combination that you want to see.

Prerequisites: 
Corequisites: 
Learning Goals: 

There could be a variety of ways that this website could be used. The learning goals would depend on what it was being used for.

 

Implementation Notes: 

I generally use this website as a way to find real examples of solid-state inorganic compounds to show in classes or use on exams.

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