Jahn teller effect

About Jahn Teller Effect in octahedral chemistry

1. Jahn-Teller Effect Presented by Meghnath Kalita Msc 2 nd semester Roll no. 06

2. Contents : History Introduction Jahn - Teller effect Z out and Z in distortion Examples Static and Dynamic JT distortion Conclusion References

3. History Hermann Arthur Jahn (born 31 May 1907,  Colchester , England; d. 24 October 1979  Southampton ) was an  English scientist of German origin.With   Edward Teller , he identified the  Jahn –Teller effect . Edward Teller  ( Hungarian :  Teller Ede ; January 15, 1908 – September 9, 2003) was a  Hungarian-American   theoretical physicist  who is known colloquially as "the father of the  hydrogen bomb ", although he claimed he did not care for the title. He made numerous contributions to  nuclear  and  molecular physics ,  spectroscopy  (in particular the  Jahn –Teller  and  Renner–Teller  effects), and  surface physics .

4. Jahn-Teller Theorem Jahn-Teller theorem states that any non linear molecule in a degenerate electronic state will distorted so as to remove that degeneracy Or, to put in a different way, when a degenerate set of orbital is occupied asymmetrically then a distortion will occur which will remove the degeneracy of the orbital. *asymmetrically filled non linear complexes shows J ahn Teller distortion *to remove degeneracy

5. If the ligand is present in Z-axis or axial axis, it will expand and bond length is increased when move toward outside is called Z-out distortion and the reversed is called Z-in distortion . The distortion of a regular octahedron, to extension along the Z-axis and comparison in x and y axes(Z-out) lowers the energy of e g orbital and increased the energy of e g orbital. Therefore, if one or three electrons occupy the e g orbital as in d4(HS), d7(LS) and d9 complexes shows huge distortion and energetically advanced. d x 2 -y 2 d z 2

6. Z-out Z-in Z-out is favourable because there is two bond increases in bond length Z-out is Lower in energy Z- is the molecular axis

7. In z-out distortion , the repulsion between electrons between metal orbital and ligand orbital is decreased due to elongation of z axis and ligand in z axis gives a repulsion with metal electrons. so, the orbital is lower in energy and also For z-in distortion the repulsion between electrons of MO is increases because they are come closer to each other and repulsion is high so, is higher in energy The lower the energy more stable the complex d z 2 d xz ,d yz d z 2

8. Molecular orbital diagram of Jahn-Teller distortion e g t 2g d xz , d yz d xz ,d yz d xy d xy d z 2 d z 2 d x 2 -y 2 d x 2 -y 2 -2/3 2/3 -1/3 1/3 1/2 1/2 -1/2 -1/2 a) Z-in distortion b) Z-out distortion δ a δ a δ b δ b Δ Δ δ 1 δ 1 δ 2 δ 2 δ 3 δ 3 δ 4 δ 4

9. Static and dynamic Jahn-teller distortion Static Jahn-Teller distortion: Complexes having measureable bond length differences are the examples of static Jahn Teller distortion SJTD shows at all condition Complexes having asymmetric filling of e g s hows SJTD Dynamic Jahn-Teller distortion : A Jahn -Teller distortion Can hop from one orientation to another, give rise to dynamic Jahn-Teller distortion Occurs only at low temperature

10. Conclusion To remove degeneracy in a non linear complex Asymmetrically filled Degeneracy is removed either by elongation or compression Elongation is favorable due to lesser in energy Lower the energy more stable the complex Detected by X-ray crystallography and electronic Spectra Static and Dynamic Jahn–Teller distortion

11. Reference Inorganic chemistry-Principle of structure and reactivity-James E. Huheey, Ellen.A Keiter, Richard L.Keiter, Okhil.K Medhi-Fourth edition- Pearson -477—481. Inorganic chemistry –Shiver and Atkins’— Atkins, Overtone, Rourke, Weller, Armstrong,--fifth edition—Oxford--

12. Thank you