Jahn dynamic effects

The stoi7 begins with studies of the molecular Jahn-Teller effect in the late 1950s [1-3]. The Jahn-Teller theorems themselves [4,5] are 20 years older and static Jahn-Teller distortions of elecbonically degenerate species were well known and understood. Geomebic phase is, however, a dynamic phenomenon, associated with nuclear motions in the vicinity of a so-called conical intersection between potential energy surfaces. 

The high lability of cP [Cu(H20)6]2+ is coincident with the operation of a dynamic Jahn-Teller effect which causes its tetragonal distortion to randomly reorientate, or invert, about the x, y, and z axes very rapidly (Fig. 8) so that the lifetime of a given distortion, r, is much less than the lifetime of a given coordinated H20 molecule, THa0 (99,... 

In the limit of strong vibronic coupling, F4S = 0, c = 5 /3, s=, c2 - s2 =, and the dynamic Jahn-Teller effect thus renders nugatory the orbital contributions to the angular momentum, and reduces the splitting, A, by a factor of two. Note in addition that the c and s quantities used in the vibronic treatment do not correspond to those of the adiabatic case, although the expressions are formally similar, so that the static distortion, A, cannot accurately be calculated from the c and s values deduced from the and 4 data. 

To summarize, the dynamical Jahn-Teller effect is found to be more significant (about one order of magnitute larger) than the GP effect as far as the... 

These TR results demonstrate that the localized model of Ru(bpy) + is valid on the timescales of electronic motions and molecular vibrations. It is virtually certain that delocalization (via, for example, intramolecular electron transfer or dynamic Jahn-Teller effects) occurs on some longer timescale. 

King RB (2005) Polyhedral dynamics and the Jahn-Teller effect. In Gielen M, Willem R, Wrackmeyer B (eds) Eluxional organometallic and coordination compounds. Wiley, New York, pp 1-37... 

Cotton, F. A., and M. D. Meyers Magnetic and spectral properties of the spin-free 3d -systems FeFj" and CoF Probable observation of dynamic Jahn. Teller effects. J. Am. Chem. Soc. 82, 5023 (1960). 

The dynamic nature ofthe Jahn-Teller effect is inhibited if the inner-coordination sphere is inhomogeneous. 

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. 

A very similar situation is presented by the dynamic Jahn-Teller effect, in which a trapped electron that has distorted its surroundings hops between two configurations with a frequency given by (6) for a proof see Sturge (1967). 

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