The excess delocalization of the spin density over the coupler is observed to reduce with an increase in HF exchange (Table ) however, the 2J value appears to increase steadily (Fig. ). Observing the ⟨ Ŝ2 ⟩ values reveals an increase in the spin contamination with the HF exchange with ⟨ Ŝ2 ⟩ BS and ⟨ Ŝ2 ⟩ T increasing from 2.0046 and 1.0021 respectively at 0% HF exchange to 2.0788 and 1.0502 at 70% HF exchange. The degree of spin contamination is known to affect the quality of the energies predicted by DFT as such it could explain the deviation in 2J with HF exchange. However, the rise in spin contamination is quite low, so its impact on the 2J values remains ambiguous. In conclusion, the HF exchange alone cannot be the major factor in determining the accuracy of the computed magnetic exchange coupling constant.