In this article, we calculate pseudocontact shifts for tetragonal high-spin Co(I1) complexes using a crystal field model. Calculated results for the dipolar field strength and its variation with temperature are compared with values derived from experimental measurements on complexes of the form Co(CH30H)5X2+. The calculation involves evaluation of the anisotropy of the magnetic susceptibility, and proceeds by the following steps: (a) from the crystal field parameters Dq, Ds, Dt, and B the three orbital wave functions of lowest energy are found. (b) The effect of spin-orbit coupling over the 12 states (three orbital wave functions coupled with four spin states) is evaluated. (c) The parallel and perpendicular components of the magnetic susceptibility are calculated, considering only these 12 states but taking into account thermal populations. It is shown that good numerical agreement can be obtained with experimental results for the dipole field strength and its temperature dependence. However, the calculations show that the linearity found when pseudocontact shifts are plotted against reciprocal temperature is only apparent, making simple interpretations, or extrapolation of the plots so obtained, meaningless.
Goodisman, Jerry, "Calculation of Pseudocontact Shifts for CO( CH30H)5X2+ Complexes" (1975). Chemistry Faculty Scholarship. 44.
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