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The Jahn–Teller effect is responsible for the tetragonal distortion of the hexaaquacopper(II) complex ion, [Cu(OH 2) 6] 2+, which might otherwise possess regular octahedral geometry. The two axial Cu−O distances are 238 pm , whereas the four equatorial Cu−O distances are ~195 pm.
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
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 ...
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).
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.
The compound is the prototypical antiaromatic hydrocarbon with 4 pi electrons (or π electrons). It is the smallest [n]-annulene ([4]-annulene).Its rectangular structure is the result of a pseudo [3] - (or second order) Jahn–Teller effect, which distorts the molecule and lowers its symmetry, converting the triplet to a singlet ground state. [4]
The metal also has six valence orbitals that span these irreducible representations - the s orbital is labeled a 1g, a set of three p-orbitals is labeled t 1u, and the d z 2 and d x 2 −y 2 orbitals are labeled e g. The six σ-bonding molecular orbitals result from the combinations of ligand SALCs with metal orbitals of the same symmetry.
The tetrahedral point group lacks the inversion operation, so the Laporte rule does not apply. [6] Illustrative of this effect are the disparate extinction coefficients for octahedral vs tetrahedral complexes of Co(II). For [Co(H 2 O) 6] 2+, which is pink, ε ≈ 10. For [CoCl 4] 2-, which is deep blue, ε ≈ 600. [5]