Copper Jahn -Teller effect

Jahn-Teller distortions cobalt and copper complexes, 2, 91 hydrates, 2, 308 Jahn-Teller effect, 5, 535 Jahn-Teller theorem, 1, 247 Jarosites... 

A minor success is also seen in complexes of d and d" ions, in which the distorted octahedral geometries observed may be rationalized (and indeed predicted) in terms of the Jahn-Teller effect, and ultimately in terms of the steric activity of the open d shell. This is a common feature in copper(n) chemistry, and you will... 

Fig. 7. The influence of the Jahn-Teller effect on bond lengths (A) of copper sulfate trihydrate (top) and pentahydrate (bottom). Note that in the trihydrate one of the Cu(II)-"OSOs bonds is short so that all equatorial Cu(Il)-"0 bonds are 1.94-1.98 A, while the axial bonds are 2.40-2.45 A.

The Cupric, Cu2+ or Cu(II) State, 3d9 The most important and stable oxidation state for copper is divalent. There is a well-defined aqueous chemistry of the Cu2+ ion, which generates the familiar blue solution when complexed with water. A large number of copper coordination compounds exist and these have been studied extensively. A strong Jahn-Teller distortion is associated with the 3d9 electronic configuration of this ion. This implies that a regular tetrahedron or octahedron about the Cu2+ ion is never observed, except in the rare occurrence of a dynamic Jahn-Teller effect. The tetragonal distortion about an octahedron can lead to a square-planar coordination which is often observed in Cu(II) oxides. 

Following two earlier, more general studies of copper(II) coordination complexes (4,55), a comprehensive LFMM study of the Jahn-Teller effect in CunN6 systems was undertaken (36) based on a selection of structures from the Cambridge Structural Database (CSD) (56,57). AOM parameters had previously been derived based on ligand field analyses of d-d spectral data (32). Agreement between theory and experiment is good (Fig. 14). 

Figure 69 Vibronic coupling for octahedral copper(II) (a) dynamic Jahn-Teller effect (alg and blg) (b) pseudo...

This general feature of both class I and class II behaviour of the copper(II) ion, i.e. the ability to exist in a high symmetry environment against the prediction of both the first- and second-order Jahn-Teller effects, is the best single piece of evidence for the cooperative Jahn-Teller effect and has recently been reviewed.432 It is generally responsible for the whole range of fluxional copper(II) stereochemistries and of the temperature variable ESR spectra of... 

In these molecular type lattices the structure of the CuN402 chromophore is independent of the structure of the host lattice, and the effect is referred to as the noncooperative Jahn-Teller effect.514 It applies to the vast majority of low symmetry copper(II) complexes involving organic type ligands, but even here cooperative effects that influence the ESR properties, such... 

Fig. 3.6. Elongations along the three principal axes of the Cu-O bonds in the hexaaqua copper(II) complex due to dynamic Jahn-Teller effects occur randomly with a correlation time of about 5 x 10-12 s.

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