Electronic spectroscopy

9 Jul 2014

5 (or 6) Slides about Biophysical Techniques

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

This Five Slides About was prepared specifically for the 2014 IONiC/VIPEr workshop Bioinorganic Applications of Coordination Chemistry held at Northwestern University July 13-18, 2014.  

It covers, in one slide per technique, the techniques of electrochemistry (Cyclic Voltammetry), Electron Paramagnetic Resonance (EPR), Circular Dichroism (CD), X-ray Absorption Spectroscopy (XAS),  NMR (specifically 2D-NMR for structural information), Chemical Exchange Saturation Transfer (CEST).  This may seem an odd list, but it was chosen to prepare participants for the papers covered in the workshop.

It is intended to be paired with a collection of application assessment Questions, posted here on VIPEr, based on actual data from the literature.  I encourage VIPEr users to add your own!

 

These slides contain animations, so they are not very useful for printing out.  

Also, there is a LOT of information (references, teaching hints, etc ) in the NOTES section of the slides.  

Course Level: 
Learning Goals: 
  •  A student should be able to explain the basics of each of the techniques included in this 5 Slides About:  CV, EPR, CEST, NMR, CD, and XAS and to apply these teachniques to the interpretation of real data.
Related activities: 
Implementation Notes: 

This LO is intended to be a quick introduction to the usefulness of these 6 techniques and their application to the characterization of bioinorganic samples.  

Ideally, one would cover each slide (each technique) and then offer students the opportunity to apply their new knowledge to a piece of real data from the literature.  I have posted several sets of Assessment Questions for that purpose.  

Time Required: 
a class period
Evaluation
Evaluation Methods: 

Assessment can be accomplished using the accompanying Assessment Questions linked to this LO and posted here on VIPEr.   I encourage others to add their own sets of Assessment question based on data in the literature.

Evaluation Results: 

This LO has not  been tested.

7 Jul 2014

Dissecting Catalysts for Artificial Photosynthesis

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

Anne’s 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: 

Students’ questions varied from the very specific to the very general.  One wanted to know what the parameter “tau” referred to, and another was confused about the concept of overpotential.  Many students weren’t sure why making carbon monoxide would be a good idea, as they see it as poisonous.  One student wanted to know if these catalysts could ever be used in ambient conditions.  Students were curious to know more about the catalytic mechanism.

Description: 

Anne asked the students in her 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.  Each student chose one article from a list of suggestions provided.  Student Hayley Johnston chose this article describing a Mn-containing catalyst for carbon dioxide reduction (Jonathan M. Smieja, Matthew D. Sampson, Kyle A. Grice, Eric E. Benson, Jesse D. Froehlich, and Clifford P. Kubiak, “Manganese as a Substitute for Rhenium in CO2 Reduction Catalysts: The Importance of Acids” Inorganic Chemistry 2013, 52, 2484-2491. DOI: 10.1021/ic302391u).  The article describes the development of a Mn-based homogeneous catalyst for electrocatalytic CO2 reduction.  Hayley met with Anne for an hour to discuss the article, then generated a list of questions drawn from the article's content.  Using Hayley’s original set of questions as a starting point, Anne and Kyle developed this literature discussion, which is suitable for use in inorganic chemistry courses.

Corequisites: 
Course Level: 
Learning Goals: 

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

  • Describe the value of CO2 reduction catalysts
  • Outline the structure of the catalyst and identify the path electrons take throughout the catalytic cycle
  • Compare and contrast the Mn-based and Re-based catalysts in terms of their CO2 reduction efficiency
Implementation Notes: 

The learning object we've developed contains fifteen questions that cover most of the article's content in great depth.  It's likely too long for an individual assignment, depending on the students' backgrounds.  We encourage instructors to pick and choose from among the questions. 

Before discussing this article, students should be familiar with the concepts of renewable fuels/artificial photosynthesis and maybe also the Keeling curve demonstrating the sharp increase in atmospheric carbon dioxide over the past two hundred years.

Students may not know that CO, carbon monoxide, is very useful. They will likely be most familiar with its dangers, not its importance in industrial chemistry. Instructors could discuss the uses of CO: synthesis of methanol (nearly all industrial methanol comes from CO), synthesis of acetic acid (nearly all of the acetic acid comes from CO and methanol), hydroformylation, and Fischer-Tropsch chemistry (which could be used to make gasoline/diesel – South Africa has used this technology for some time).

A discussion of cyclic voltammetry would also be useful, including discussing the role of ferrocene as an internal reference. We have referenced the “five slides about” LO Cyclic Voltammetry created by Prof. Chip Nataro as a related activity.

In terms of placing this manuscript in context, previous studies included rhenium complexes, which work without added proton sources but are much improved in the presence of proton sources. The seminal work on rhenium complexes was performed by Jean-Marie Lehn (of supramolecular Nobel Prize fame) in the 1980s.

A comprehensive review of the history of these Re and Mn complexes from their discovery up to early 2013 can be found in “Chapter Five  – Recent Studies of Rhenium and Manganese Bipyridine Carbonyl Catalysts for the Electrochemical Reduction of CO2” Kyle A. Grice and Clifford P. Kubiak Advances in Inorganic Chemistry201466, 163-188  (see web resources below).

Several more recent papers have also been published on the Re and Mn systems from the Kubiak group and other groups since early 2013, including mechanistic studies of the Re and Mn systems using a variety of methods. A forward search of the Mn manuscript by Smieja et al. can be used to find these articles.

For more detailed information about IR-SEC, see this reference and references therein: Charles W. Machan, Matthew D. Sampson, Steven A. Chabolla, Tram Dang, and Clifford P. Kubiak Organometallics, 2014, ASAP  (see web resources below).

 

 

Time Required: 
45 minutes
11 Jun 2014

A Jablinko game to promote learning of excited state transitions

Submitted by Alycia Palmer, The Ohio State University
Evaluation Methods: 

The learning goals were informally assessed by observing student participation in the class game and through discussion with students during the game. Also, notes taken during the game by the students were used to evaluate if students could make sense of the game.

Evaluation Results: 

Initially, students were shy to volunteer to go up to the board, but after the first round, student involvement increased. It seemed that that response portion of the game was dominated by a few students, so in the future the game may be more effective by dividing the class into teams.

 

Students were unsure how to note the result of one turn on their handout. They would just write down the transition name (e.g. T1 to S0) instead of drawing on the Jablonski diagram. In the future, to help students better connect the game to the Jablonski diagram, the instructor may wish to have a volunteer draw the transition on the chalkboard, for the whole class to see.

 

Over the course of ~10 minutes of playing the game, the students became very quick at answering the name of the transition. However, students did not seem more comfortable drawing the transition, so more time should be spent on helping students to complete the worksheet during the game.

Description: 

The in-class game Jablinko was designed to make learning excited state transitions fun. To play, a student chooses an excited state by placing a game chip at the top of the board, then the chip can “vibrationally cool” by bouncing through the pegs, and finally “transition” to a lower energy state in the bottom row. The students then compete to be the first to name the transition (e.g. S1 to T1 is called intersystem crossing).

Jablinko is intended to be used following an in-class discussion on photochemistry, using the lecture slides provided with these facilitator notes. The Jablonski diagram for [Ru(bpy)3]2+ is central to the discussion on excited state transitions and is relevant as an introduction to upper-level advanced inorganic laboratories that investigate emission or excited state quenching properties.

Learning Goals: 
  • Explain excited state processes through the use of a Jablonski diagram
  • Describe how transitions occur between electronic states
  • Learn how to draw a transition provided from the game on a blank Jablonski diagram
Corequisites: 
Course Level: 
Equipment needs: 

Computer/projector for powerpoint slides. It would be beneficial to have a means of writing on the slides while delivering the information to students, but this is not required.

 

Construction of the Board

A ­­­2’ × 4’, 1/8” thick, holes 3/16” width, standard white pegboard was purchased from a home improvement store for under $20. The board was used as purchased, thus not cutting was required. The holes are 1” apart in all directions. 1-1/4” length, 3/16” width dowel pegs were purchased for less than $2 and used on the board to guide the Jablinko chip. Pegs were inserted leaving three empty holes between sets of pegs, and two empty rows between filled rows in a staggered fashion (see photo). Wells were created at the bottom using peg placement: columns 5 pegs high with a 5-peg-wide gap between. These can be arranged to suit your chip size and it is recommended that you identify your Jablinko chip before placing pegs onto board. Jablinko chips were crafted from the plastic covers used on cardboard poster tubes. Cardstock was used to label the board and paper inserts were created to fit in the caps of the poster tubes. Additional pegs were inserted where needed around the edges of the board to keep the chip from falling off of the board. This entire board was crafted in less than 2 hours.

Implementation Notes: 

Jablinko is intended to be used following an in-class discussion on photochemistry, using the lecture slides provided with these facilitator notes. One suggestion for how to organize the class period is (1) to have the instructor lead the class discussion on slides #1—6, then (2) invite students to play Jablinko, and finally (3) the instructor will finish the class discussion with slide #7. Comments for the instructor are included on each slide to facilitate the transfer of information into your own classroom. Additionally, hidden slides are includes that show hand-written text and drawings that were made during the discussion period with a stylus.

Time Required: 
One 55-minute class period
30 Apr 2014

Inorganic Spectroscopy Introduced Using an Interactive PhET Simulation (Part 1)

Submitted by Alycia Palmer, The Ohio State University
Evaluation Methods: 

The learning goals were informally assessed through conversations between the facilitators and students during both class periods (for this and the related LO). Also, student worksheets were collected after class to analyze student responses. Finally, students were asked to complete a survey about the activity and if they feel that the PhET activity should be used in future classes to introduce the topic of inorganic spectroscopy.

Evaluation Results: 

Students were engaged with the Molecules and Light activity which utilized the PhET simulation. Groups of 3-4 students are a good size to encourage all students to be involved in discussion. On the portions of the worksheet that asked for generalizations, the responses were vague and only scratched the surface. In the future, the instructor may wish to lead a class discussion to brainstorm for ideas about which features of molecules make them reactive to the four types of radiation in the simulation.

At the end of the second class period (after the second activity described in the related LO), students were asked to evaluate the PhET simulation and accompanying worksheet. Eleven (out of 16) students responded that the simulation should be used in future classes to provide background before topics about inorganic spectroscopy are discussed. Only one student said that it shouldn't be because it only introduced basic concepts. Four students either did not answer or did not take a definite stance.

Overall, students were satisfied with the PhET simulation and the accompanying worksheets. Also, based on the student responses to the worksheets, the instructors feel that the learning goals were met.

Description: 

A guided-inquiry activity for the interactive PhET simuation "Molecules and Light" was created to introduce upper-level inorganic laboratory students to inorganic spectroscopy. The activity included here is the first part of a two-day discussion. This activity instructs students to use the PhET simulation "Molecules and Light" to explore how various molecules interact with different energies of electromagnetic radiation (microwave, infrared, visible, ultraviolet). This activity can also be used in a general chemistry setting as the topics discussed are very basic.

The PhET simulation "Molecules and Light" was chosen because it integrates with the inorganic laboratory "Linkage isomerism of nitrogen dioxide." The simulation helps students to visualize how nitrogen dioxide gas interacts with infrared light, and in the laboratory, students collect FT-IR spectra of nitrogen dioxide coordinated to a metal.

The second part of the activity ("Inorganic Spectroscopy Introduced Using an Interactive PhET Simulation (Part 2)") builds on topics learned by interacting with the PhET simulation. That activity is most useful for upper level inorganic laboratory students who will be performing spectroscopy experiments. Materials for Part 2 are also shared on VIPER.

A special thank you goes to the other contributors of these activities: Julia Chamberlain, PhD; Ted Clark, PhD; and Rebecca Ricciardo, PhD

 

Learning Goals: 

Students should be able to:

  • describe how a set of example molecules interacts with light of varying energy
  • identify characteristics of molecules that are associated with an interaction with light
  • construct a set of guidelines that generalize how molecules react with light of varying energy (microwave, infrared, visible, ultraviolet)
  • apply these guidelines to predict the reactivity with light for a small molecule which is not in the simulation. The instructor may wish to assign molecules that are shown in another simulation "Molecule Polarity" in order to provide nice visualizations. These include: ammonia, hydrogen cyanide, formaldehyde, methane, CF4, and CH2F2.
Equipment needs: 

In order for students to successfully use the PhET simulation, one computer is suggested per 3-4 students.

 

Prerequisites: 
Corequisites: 
Implementation Notes: 

Facilitator notes are included as comments on all documents and can be viewed by selecting "Show Comments" under the review tab in Power Point or "Show all markup" under the review tab in Word.

This activity was implemented in a lecture setting with a class of 16 students. The group work was implemented during the 1-hour class that meets weekly and accompanies the 3-hour inorganic laboratory. Students were instructed before class to bring their own computer and to download the simulation.

Time Required: 
One 55-minute class period
19 Mar 2014

First use of the term "bioinorganic"

Submitted by Joshua Telser, Roosevelt University
Description: 

Thanks to information first provided to me by Prof. Brian M. Hoffman, Northwestern University, I believe that the first documented use of the term "bioinorganic chemistry" occurred at a meeting held at Virginia Tech (VPI&SU) in June, 1970. This meeting was jointly organized with Canadian researchers and was thus an international meeting.

This meeting resulted in an Advances in Chemistry Series book, which has the following URL:

http://pubs.acs.org/doi/book/10.1021/ba-1971-0100

The topics covered are still relevant, and include articles by many leading researchers (e.g., Harry Gray and Ronald Breslow  - to pick one each from inorganic and organic areas).

I plan on showing this TOC in my Bioinorganic class to demonstrate what the topics of interest then were, and give some historical perspective to the next generations.

Another aspect of this literature discussion is to demonstrate errors that exist in the chemical literature, in this case, of a historical rather than a quantitative (actual chemical) nature.

A statement in the following article, which is otherwise very interesting, inspired this attempt to correct the historical record:

http://www.sciencedirect.com/science/article/pii/S0014579312001160

Helena Santos, FEBS Letters Volume 586, Issue 5, 9 March 2012, Pages 476–478. "António Xavier and his contribution to the development of Bioinorganic Chemistry".

"In 1979, in collaboration with H.A.O. Hill, he [Prof. Xavier] organized a NATO-ASI conference in Tomar, Portugal, on “Metal Ions in Biology” which would become a memorable milestone in the history of Bioinorganic Chemistry. According to Robert R. Crichton, this was probably the first Bioinorganic Chemistry meeting..." [emphasis mine]

This is false, as readily demonstrated by the above description of the Virginia Tech meeting, which was nine years earlier. Moreover, the statement attributed to Prof. Crichton is totally incorrect even absent knowledge of the Va. Tech meeting.

The Portugal meeting was titled “Metal Ions in Biology” - not "Bioinorganic Chemistry" in any variant. The term “Metal Ions in Biology” had already been in use for many years (since 1962) as (first as part of) the title of the Gordon Research Conference on this topic. This can be easily seen from the GRC web site:

http://www.grc.org/conferences.aspx?id=0000155

The history of this conference is of interest on its own, in terms of the researchers involved as chairs over the years (e.g., Prof. Richard H. Holm as Chair in 1973, who likely ensured a strong bioinorganic content). All conferences starting with 1995 have active links so that the topics over the last nearly 20 years can be examined in detail.

There was a full-blown international bioinorganic chemistry meeting that took place in Vancouver, BC Canada in June 1976, thus preceeding the Portugal meeting by three years. This Vancouver conference is sometimes referred to as "ICBIC-0", as noted by Prof. Chris Orvig, the organizer of ICBIC-11 in Vancouver on August 7-12, 2011. Hence, he called ICBIC-11 the "Jade Anniversary" (jade = 35, according to Hallmark Cards, the definitive source for such matters).

As is so often the case, the best explanation is due to Harry B. Gray, and the following article from 2003, is highly recommended for a history of bioinorganic chemistry as well as for an overview of the research areas.

Proc Natl Acad Sci U S A. Apr 1, 2003; 100(7): 3563–3568. doi: 10.1073/pnas.0730378100

http://www.pnas.org/content/100/7/3563.full

Of relevance here is the following (a few comments added):

"During June 16–20, 1976, several hundred chemists and biologists assembled at the University of British Columbia (UBC) to listen to 13 lectures and discuss recent developments at the interface of inorganic chemistry and biology. To be sure, there had been many previous meetings at which this new science was featured, notably one in Blacksburg, Virginia (1), and several others on special topics that were held during the 1950s and 1960s. As the old timers will remember, the Gordon Research Conference on Metals in Biology (MIB GRC, originally called Metals and Metal Binding in Biology) had its inaugural meeting in August 1962, at the New Hampton School, New Hampshire. Interest in the conference from the inorganic side grew rapidly, and in 1970, with Paul Saltman running the show, the MIB GRC tradition of close interactions among biologists, biochemists, and inorganikers was firmly established.

With apologies to the organizers and participants of earlier gatherings of the faithful, I will start with the UBC meeting, because it was the immediate precursor of the now famous International Conference on Bioinorganic Chemistry (ICBIC) series (and, accordingly, often called ICBIC-0!), created by Ivano Bertini and held first in Florence in 1983, with highly successful encores in Portugal [1985], The Netherlands [1987], Boston [MIT, 1989; K. D. Karlin organizer], Oxford [1991], San Diego [UCSD, P. Saltman organizer], Japan [1997], Germany [1995], and Minneapolis [UMinn, L. Que, Jr. organizer]. On its 10th anniversary, in 2001, the ICBIC returned to Florence, as well it should have done, and on it goes, with ICBIC-11 set for Cairns, Australia, in July of this year [2003]." [2007 in Vienna, Austria; 2009 in Nagoya, Japan; 2011 in Vancouver, BC as noted above; 2013 in Grenoble, France; 2015 to be in Beijing, PR China; 2017 to be in Brazil].

Prerequisites: 
Corequisites: 
Learning Goals: 

Appreciation of the continuing themes of research interest in bioinorganic chemistry, e.g., dinitrogen fixation.

Appreciation of the history of the area and the "giants on whose shoulders we stand".

Subdiscipline: 
Course Level: 
8 Mar 2014

Five Slides about Tanabe-Sugano Diagrams

Submitted by Sabrina G. Sobel, Hofstra University
Description: 

Brief introduction to d-orbital splitting, Russell-Saunders coupling, and application to UV-Vis spectroscopy using Tanabe-Sugano diagrams

Prerequisites: 
Topics Covered: 
Subdiscipline: 
Learning Goals: 

A student should be able to:

1. Draw a d-orbital splitting digram for an octahedral complex.

2. Determine the L-S coupled ground state term for the metal cation.

3. Read a Tanabe-Sugano diagram to predict or understand a UV-Vis spectrum.

Course Level: 
Implementation Notes: 

The Five Slides have web links as resources to expand the discussion presented on these slides. The slides should be used as an introduction, then problems should be attempted to implement the knowledge.

Time Required: 
The presentation itself, including class discussion, should take 15-20 minutes, especially if one stops to give examples along the way.
Evaluation
Evaluation Methods: 

In-class and homework problems involving

(1) the identification (in a complex) of the charge and d-electron count of the central transition metal cation,

(2) determination of the ground state L-S coupled term,

(3) choosing the correct Tanabe-Sugano diagram for the d-electron count,

(4) predicting whether the d-electrons will be in a high-spin or low-spin configuration, baed on metal identity, charge, and ligand identities, and

(5) prediction of explanation of a UV-Vis spectrum using this information.

Evaluation Results: 

I have had mixed success with students. The shortcut to finding the GS term works well. Students have trouble deciding between high spin and low spin for a particular complex, especially with ammonia as a ligand.

24 Jan 2014

Student choice literature-based take home exam question

Submitted by Hilary Eppley, DePauw University
Evaluation Methods: 

This question was 30 points on a 100 pt take home exam (the year I did this, there was also a 100 point in class exam as well).   I've included the title page of the take home exam as well as this question.   

The grading scale allowed most of the points for the student chosen course content to highlight.   Of the 30 points, 10 focus on chemical information skills, 20 on summarizing the article and analyzing it using concepts from the class.   

Evaluation Results: 

I gave back a number of the exams before I was able to tally, but of the ones I had remaining: 

60% got full credit on the part a (those who missed neglected to include a summary) 

100% got full credit on part b

60% got full credit on part c (those who missed searched by formula rather than connectivity or provided an insufficient explanation of what they searched on 

100% got full credit on part d

On part e, answers varied widely from 7/17 to 15/17, with an average of 12/17 or a 70%.  

In some cases they lost points for just repeating things verbatim from the paper without explaining them to show they understood the concepts.   The main reason for loss of points however was just a lack of effort at picking apart the paper for parts that were relevant to the course content.   

They were able to successfully apply things such as electron counting and mechanism identification in a catalytic cycle, point groups, descriptions of sigma and pi bonding in ligands.   

 

Description: 

During my junior/senior level inorganic course, we did several guided literature discussions over the course of the semester where the students read papers and answered a series of questions based on them (some from this site!).  As part of my take home final exam, I gave the students an open choice literature analysis question where they had the chance to integrate topics from the semester into their interpretation of a recent paper of their own choice from Inorganic Chemistry, this time with limited guidance.  I also included a number of questions that required them to make use of various literature search tools to show that they had mastered those skills.   I gave them a list of topics that they could incorporate, but based on the poor quality of the responses I received, I encourage you to be more specific in your instructions.  I'd love to see some new versions!      

Corequisites: 
Course Level: 
Prerequisites: 
Learning Goals: 
Students will
  • choose a recent paper that interests them from Inorganic Chemistry
  • summarize why a particular paper is important to the field of inorganic chemistry
  • use literature search tools including Web of Science, Cambridge Structural Database, and SciFinder Scholar to find information aobut cited references, structurally similar compounds, and the authors of the paper
  • integrate ideas such as bonding models, symmetry, spectroscopy structural data, and chemical reactivity from class into a detailed analysis of aspects of the paper

The instructor will

  • get up to date on new literature for possible new literature discussions
  • get a chance to stretch his/her own intellectual muscles on some papers perhaps outside of his/her area of expertise
Implementation Notes: 

The students were given the take home exam about 1 week before it was due (but that was during the final exam period).   The format of the chemical information questions were similar to things they did earlier in the class, however the analysis of the paper was much more open ended, giving them the freedom to choose a paper that interested them and to presumably focus on concepts from the class that they felt comfortable with.   I gave them a date range from April 1 - April 30, 2012 for their paper because those were the most recent issues at the time.  If you use this LO, you will probably want to change those dates to more recent ones.   

Time Required: 
at least an hour, possibly more depending on the student
23 Jan 2014

Electronic Absorption Spectroscopy of Aquated Transition Metal Ions

Submitted by Zachary Tonzetich, University of Texas at San Antonio
Evaluation Methods: 

The students prepare a laboratory report, usually at the discretion of the teaching assistants, reporting their data, analysis, and conclusions. Several questions are also provided in the lab manual that can be used for assessment. 

Evaluation Results: 

We have conducted this experiment twice over the last two semesters. It runs quite smoothly with class sizes of 25 - 30, where students typically work in groups of 2 or 3. The results obtained by the students are generally quite good, and match the true numbers of waters of hydration for each metal salt, save iron(II) sulfate (see implementation notes). I cover the inorganic chemistry concepts during lecture so that the students who haven't had too much cyrstal field theory are prepared to answer the questions in the lab manual.

Description: 

I developed this laboratory experiment for our instrumental analysis class. The course is taken by junior and senior chemistry majors, who for the most part have had one inorganic chemistry course and some physical chemistry. The laboratory is operationally very simple and has students record the UV-vis spectra of transition metal sulfate salts in water using volumetric technique. They record the molar absorptivities for each peak and use this data to determine the number of waters of hydration for each salt by comparing with literature absorptivity values. We withhold the number of waters of hydration from the commercial bottles and have the students proceed using only the ionic formulas. They thus caluclate values that are less than the literature values and must use the ratio of lit/calc to determine the true molecular weights and hence number of waters of hydration. This part of the experiment is more analytical in nature and introduces students to the UV-vis instrument while reinforcing the practice of preparing solutions of precise concentration.

As an additional aspect of the laboratory, the students use their data to calculate the crystal field splitting parameter for each of the hexaqua complexes using Tanabe-Sugano diagrams. I also include the spectra of two tetrachlorometallate salts, [NiCl4]2- and [CuCl4]2-, so students can compare band energies and intensities between octahedral and tetrahedral complexes. The classic hexaqua spectra are usually shown in textbooks, but it is neat to have the students generate the data themselves. Unfortunately, the experiment requires a UV-vis spectrometer with near-IR capabilities. We are fortunate enough to have one, but not all universities may. 

Prerequisites: 
Learning Goals: 

The goals of this experiment are to have students 

Equipment needs: 

UV-vis spectrophotometer with near IR capabilities (250 - 2000 nm).

Implementation Notes: 

See the Experiment_notes.docx file under the faculty-only files for implementation notes and example spectra.

Time Required: 
3-hour laboratory period
3 Jan 2014

Crystal Field Theory: Analysis of the Iron Sites in Gillespite

Submitted by Zachary Tonzetich, University of Texas at San Antonio
Evaluation Methods: 

Throughout this activity, students should determine the orbital diagrams, term symbols and normal mode symmetries for each step. I try to guage their understanding by seeing how successfully they are able to accomplish these exercises. I also look to see if they are able to come to the final conclusion regarding the electronic structure of the iron site by taking into account the vibronic polarization data.

Evaluation Results: 

Most of my students (Ph.D., M.S., and advanced undergraduate) are able to follow this activity successfully, especially the orbital diagrams and normal mode symmetries. Many get confused with the difference between orbital diagrams and electronic states, and this activity therefore serves as a nice means of reinforcing these concepts. Some students also get lost when trying to determine direct products of irreducible representations for the assignment of term symbols or the symmetry of transition moment integrals.

Description: 

This in-class activity explores the electronic structure and spectroscopy of the square-planar iron(II) sites in the mineral gillespite through a crystal field theory approach. This activity is designed for an advanced inorganic chemistry course where group theory and more advanced topics in ligand field theory are taught. The activity is based on the work detailed in the paper: Burn, R. G.; Clark, M. G.; Stone, A. J. Inorg. Chem. 19665, 1268-1272. I typically use this activity to review for examinations because it brings together many of the central ideas I cover as part of crystal field theory such as orbital diagrams, term symbols, vibronic polarization, selection rules, and rudimentary magnetism.

 

Learning Goals: 

The primary goal of this activity is to have students apply their knowledge of CFT and group theory to explain the electronic structure of a transition metal ion in a mineral (the original use of CFT!). The actiivty uses the example of a square-planar complex, which forces students to make a departure from their usual routine of evaluating octahedral and tetrahedral complexes with CFT. Students should also gain an appreciation for the technique of polarization in electronic spectroscopy and how it can be used to identify certain transitions.

Equipment needs: 

None.

Subdiscipline: 
Course Level: 
Corequisites: 
Implementation Notes: 

I display the pdf file on screen in front of the class, being careful to keep the answers to any questions covered until the students have had time to work on them. Students work individually or in groups on each question and then we discuss each answer (including any questions students have) prior to proceeding through the document. The students will need a set of character tables. In addition, including correlation tables and direct product tables will expedite the activity (see web resources). Having the .cif file of gillespite handy is also nice to be able to show students using Mercury. I have attached one such file from the paper: Amer. Mineral. 197459, 1166-1176 in the faculty files along with the MS word document of the activity in case people want to change any aspects.

Time Required: 
75 minutes
27 Jun 2013

Introduction to Synchrotron Radiation

Submitted by Megan Strayer, The Pennsylvania State University
Description: 

This 5 slides about gives a basic introduction to synchrotron radiation.  Information includes how the particles are accelerated, how they travel to the individual instruments, and where synchrotrons in the USA are located.

Prerequisites: 
Corequisites: 
Learning Goals: 

After going over the slides, students will be able to:

  1. Explain how the synchrotron energy is generated.
  2. List experimental techniques that use synchrotron radiation.
  3. Construct a list of the pros and cons of synchrotron radiation and use that knowledge to determine if a specific synchrotron experiment is worth pursuing.
Implementation Notes: 

These slides can be used to give students an idea of the basic concepts of synchrotron radiation. After going through the slides, a helpful exercise is to give the students an experiment and have them weigh the pros and cons of using synctroton radiation for the experiment versus a more traditional approach. For example, would it be worthwhile to use synchrotron radiation to obtain X-ray diffraction data on 30 nm crystalline particles? How about 2 nm crystalline particles?  Amorphous particles?

Time Required: 
One class period
Evaluation
Evaluation Methods: 

Students could work in small groups to determine what kind of experiments are worthwhile to submit an abstract to a synchrotron source and which experiments would be sufficient to run without the synchrotron radiation.

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