A Contact shift

We perform here a sample calculation to show that Eq. (6.9) 

Magnetically Coupled Dimers in the High-Temperature Limit 

As expected, this contribution is the same as that of the isolated ion. 

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No significant pseudo-contact shifts could be induced in the spectra of dibenzothiophene, its sulfoxide, or its sulfone, with Eu(dpm)3 although a marked shielding of the protons of one ring was observed in the spectrum of the chromium tricarbonyl complex of dibenzothiophene,presumably due to a contact shift mechanism. 

Paramagnetic tons may alter NMR chemical shifts by what is known as a contact shift or by what is known as a pseudoconlact shift Consult an NMR book and explain II difference... 

This is not in accord with theory for pure 7r-delocalization between metal and ligand which predicts that a-contact shifts for H and be of opposite sign. However, possible large pseudocontact shifts in the low spin state of these complexes complicate the issue. For a series of Fe(dtc)2X complexes (X = Cl, Br, I), however, accurate estimates of pseudocontact shifts from magnetic susceptibility data can be made. 

A contact shift study (87) of various benzazole [14] adducts of... 

Although the use of shift reagents is well established, the analysis of the factors responsible for the observed shifts continues. The discussion concerns the relative importance of contact (spin delocalized) and pseudocontact (anisotropic) shifts. Substituted adamantanes and bicyclo[2,2,l]heptanes are suitable rigid systems with which to analyse such shifts. With mono-functional subtrates, shifts with most tris(dipivalomethanato)lanthanides were best explained by formation of 1 1 complexes in which the effect of the dominant pseudocontact shift was modified by a contact shift. This contact shift is only important very close to the lanthanide as the magnitude of the shift decreases very greatly with distance. With bifunctional compounds the analysis is more complex. 

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