My Notes
Categories
This article focuses on a theoretical analysis of K-edge X-ray Absorption Near Edge Structure (XANES) of Fe(CO)5 in the D3h and C4v geometries. For the context of a one semester inorganic chemistry / physical inorganic chemistry course, the authors use computational methods and experimental X-ray techniques to generate the XANES spectra of two different geometries of Fe(CO)5. Densities of states are used to show overlap between specific orbitals (Fe p with C p), indicating pi-backbonding. The spectral analysis indicates how the structural geometry affects the peak height and reveals the ground state and more abundant structure of Fe(CO)5.
This was initially used (and thus phrased) as a final exam review for MO theory and group theory with elements of spectroscopy as the authors use Walsh diagrams to show the change in MOs from D3h to C4v and their respective symmetry assignments. Guiding questions based on discussion questions can focus on elements of assigning point groups, deriving character tables, assigning characters to particular orbitals, coordination chemistry -- bonding, etc.
| Attachment | Size |
|---|---|
| Discussion Questions for Students | 22.16 KB |
After reading the article and answering the discussion questions, students will be able to:
- Make connections between MO theory (Walsh diagrams), Group Theory in orbital labels and point group identification, and how the electronic structure affects spectroscopic peaks in the context of X-ray Absorption Spectroscopy (XAS).
- Review Group Theory and Point Group Identification
- Review MO theory and Walsh Diagrams
- Review effect of strong field ligands on the orbital energies of d orbitals
- Learn about XAS as a characterization technique
- Learn how Densities of States (DOS) are used in computational analysis of compounds and materials.
I opted to not focus on the specific computational methods and software since that section is fairly technical and doesn't impact the interrelations between MO theory, group theory, and spectroscopy.
I included guiding questions like "What is the difference between C4v and D3h?", "What happens to the orbitals?" to help the review process get going.
Any of the questions can be adjusted based on how you teach your course. More questions can be added to focus on topics like pi-backbonding, strong field ligands effects of d orbital splitting, point group identification reason(s), character tables, etc. The pre-edge does also contain spin-forbidden s-d transitions since K-edge XANES is a 1s to nd transition, so additional elements of spectroscopy can be included in the discussion questions.
I gave the students 5 days to read it before class (assigned on a Wednesday, discussed the following Monday).
Evaluation
I just gauged student participation during the discussion and briefly looked over the discussion questions. An integrated multi part question using information from this paper (or a hypothetical model that has a similar idea) could be used for an exam or a final exam.
Students understood the differences between D3h and C4v and how it affects X-ray Absorption spectra.