Can you suggest to me the possibility (structure / reduction properties) of Jahn teller distorted complex under variable temperature in following instrumentation.
1. Raman, 2. Photo luminescence, 3. EPR, 4. VSM, 5. PPMS.
[A]Raman
In both the infra-red and Raman spectra, a Jahn-Teller active vibration may give rise to overtones of extremely high intensity but irregular spacing.
REFERENCE:
Phil. Trans. R. Soc. Lond. A 21 December 1961 vol. 254 no. 1041259-294(1961).
[B] Photo luminescence
For selected systems, the influence of the Jahn-Teller effect can exceed the red shift related to a symmetry conserving deformation in the relaxed excited state.
physica status solidi (c) 01/2006; 3:3561-3564.
[III] VSM
Due to JTE , the T2 g and Eg sets[ octahedral ] or T2 and E sets[ tetrahedral] of orbitals further lose their degeneracy. This makes the filling of orbitals with electrons altogether diffent from those if there were no JTE.The maximum JTE is expected in Cu(II) and Co(II). The effect of JTE on changing the magnetic properties of complexes is explained by taking only an example of d^7 [Co(II)] complexes.
If there were no JTE, the filling of electrons in the two sets should be t2g^5 eg^2 with three unpaired electons . So the magnetic moment should have been corresponding to three unpaired electron[ equal or more than 3.873BM] .
But depending upon the extent of distortion due to JTE and temperature , the splitting of orbitals may be as follows:
[ B2g^2, Eg^4,A1g^1, B1g], [B2g^2,A1g^2, Eg^3, B1g].
Accordingly, there will be one unpaired electron and magnetic moment will be 1.732 or some what more.
[IV]EPR
EPR, by far, is the best technique to ascertain the presence/ extent of JTE in complexes.
Though many first transition metal ion complexes exhibit JTE, but it is best explained in Cu(II) complexes. If Cu(II) complex were an ideal octahedral or tetrahedral[ in fact, there are hardly any ], then it should show one peak[ Fig-I].As the JTE sets in, there comes distortion[ Z-out/ Z-in or elongation/ compression] and a typical dimeric suare planar Cu(II) complex like dimeric Cu(II) acetate monohydrate[ Cuac2.H2O]2 show ESR spectra is shown in Fig-II. with the two “g’ values named as g ll and g┴ and generally have relative magnitude: g ll > g┴> ge [2.0023]*. With the increase in JTE strength, which depends upon is ligand field strength and temperature, there could be seen three values –g1, g2 and g3.[ Fig-III]
[V]PPMS
As I hardly know PPMs,so I am not discussing it. Yes; It can be used for JTE. I am giving only the reference of a paper as it belongs to one of our worthy RG member.
Journal of Physics Condensed Matter . 12/1998; 7(17):3247.
* In some cases[ rarely], the trend changes and the values may be less than 2.oo23.
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