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The Jahn–Teller effect (JT effect or JTE) is an important mechanism of spontaneous symmetry breaking in molecular and solid-state systems which has far-reaching consequences in different fields, and is responsible for a variety of phenomena in spectroscopy, stereochemistry, crystal chemistry, molecular and solid-state physics, and materials science.
In their early 1957 paper on what is now called pseudo Jahn–Teller effect (PJTE), Öpik and Pryce [2] showed that a small splitting of the degenerate electronic term does not necessarily remove the instability and distortion of a polyatomic system induced by the Jahn–Teller effect (JTE), provided that the splitting is sufficiently small (the two split states remain "pseudo degenerate ...
The pyramidalization and energies of inversion of group 15 :MR 3 (M = N, P, As, Sb, Bi) and group 14 •MR 3 molecules can also be predicted and rationalized using a second-order Jahn-Teller distortion treatment. The “parent” planar molecule possessing D 3h symmetry has frontier orbitals of a 2 ” (HOMO) and a 1 ’ (LUMO) symmetries
Complexes such as this are called "low spin". For example, NO 2 − is a strong-field ligand and produces a large Δ. The octahedral ion [Fe(NO 2) 6] 3−, which has 5 d-electrons, would have the octahedral splitting diagram shown at right with all five electrons in the t 2g level. This low spin state therefore does not follow Hund's rule.
For a free ion, e.g. gaseous Ni 2+ or Mo 0, the energy of the d-orbitals are equal in energy; that is, they are "degenerate". In an octahedral complex, this degeneracy is lifted. The energy of the d z 2 and d x 2 −y 2, the so-called e g set, which are aimed directly at the ligands are destabilized.
Known for his "life-long years of experience in theoretical chemistry" [1] working on the electronic structure and properties of coordination compounds, Isaac B. Bersuker is “one of the most widely recognized authorities” [2] in the theory of the Jahn–Teller effect (JTE) and the pseudo-Jahn–Teller effect (PJTE).
In the [Mn(H 2 O) 6] 2+ metal complex, manganese has an oxidation state of +2, thus it is a d 5 ion. H 2 O is a weak field ligand (spectrum shown below), and according to the Tanabe–Sugano diagram for d 5 ions, the ground state is 6 A 1. Note that there is no sextet spin multiplicity in any excited state, hence the transitions from this ...
In an Orgel diagram, the parent term (P, D, or F) in the presence of no ligand field is located in the center of the diagram, with the terms due to that electronic configuration in a ligand field at each side. There are two Orgel diagrams, one for d 1, d 4, d 6, and d 9 configurations and the other with d 2, d 3, d 7, and d 8 configurations.