Finally to compare, the two QC hyperfine tensorbased shifts in the two Co(II) complexes, we calculated the dipolar and contact contributions using the three approaches (eq. 10 to eq. 9). The QC shifts in the [Co(AcPyOx) 3 (BPh)] + complex subject to the variation of the model equations and the QC Hilbert spaces are comparable from Tables S15, S16. We summarize the same for the CoTp 2 complex here in Table 2 for a quick comparison. QC shifts evaluated according to the mPV or BB approaches quite successfully estimated the paramagnetic chemical shifts in the two Co(II) complexes based on the SO-CAS based description of the two ground KDs and unrestricted DFT based evaluation of the hyperfine tensors as also previously reported by Vaara et al. for the CoTp 2 . This may result in the validation of the two-KDs model and a SD description of the dipolar shifts (due to the use of DFT hyperfine tensors) for the QC evaluation of paramagnetic chemical shifts in these complexes. When the x-axis in Fig. incorporates PCS from an experiment, a strong correlation between the point SD shifts based on the SO-CAS description of the paramagnetic center and the experimental PCS does not necessarily imply that the PCS is primarily SD in origin, as assumed previously . Already the assumption has led to a "puzzle" in the literature regarding whether PCS evaluation should be based on ∆ χ s ax or ∆ χ ax , ultimately resolved by Lang and Cerofolini et al. who showed that ∆ χ ax should be used. The good agreement of the calculated NMR shifts according to mPV or BB approaches in Table (and in Table ) including ZORA-PBE0 dipolar hyperfine tensor over SO-CASSCF does not again validate the dipolar shifts in this complex as primarily SD in origin. Instead, this discrepancy compared to Lang and Cerofolini et al. arises from the significant overestimation of magnetic anisotropy ∆ χ ax from the two spin Hamiltonian parameters based approaches. As the magnetic anisotropy ∆ χ ax and hence χ s are correctly evaluated according to the VV approach in CoTp 2 incorporating excited state contributions beyond the two ground KDs, the shortcomings of the DFT-based tensors in the QC evaluation of the dipolar shifts are revealed in Table . On the other hand, evaluation of SO-CASSCF dipolar hyperfine tensors is limited to the two lowest KDs, resulting in overestimation of Table : Comparison of isotropic χT (in cm 3 Kmol -1 and at 300 K) and anisotropic ∆ χ ax = χ ∥χ ⊥ (in 10 -8 m 3 mol -1 ) paramagnetic susceptibilities in the two Co(II) complexes evaluated from the different approaches with the experimentally determined values from Refs. . The spin-only contributions are also evaluated for each approach and denoted by the superscript "s". : Semi-classical point spin-dipolar (eq. S5) vs QC calculated hyperfine tensor based dipolar shifts in the [Co(AcPyOx) 3 (BPh)] + complex according to eq. 1 where χ s tensor has been determined from SO-CASPT2 results using mPV formalism.