The magnitudes as calculated by B3LYP, M06, and PBE0 functionals are 175.02 cm -1 , 193.02 cm -1 and 195.56 cm -1 respectively. While all the density functionals correctly predict the ferromagnetic ground state, the magnitude of magnetic exchange coupling obtained is inconsistent. This observation prompted us to explore the various exchange-correlation functionals like GGA, meta-GGA, hybrid meta-GGA, and range-separated functionals, and their effect on the magnitude of magnetic exchange coupling. Among the GGA functionals utilized, OLYP produced a 2J value of 129.7 cm -1 , which is quite close to the experimental value. We also observe that on average, the GGA functionals have the least deviation from the experimental value (Table ). However, the spin density distribution on the diradical reveals a large delocalization from the spin centers to the coupler, which in the case of OLYP is 0.25 µ B Å -3 in the triplet state. This is due to the self-interaction errors arising from the local nature of the exchange-correlation term in GGA functionals. The comparatively large spin delocalization suggests that the magnitudes predicted by the GGA functionals are less reliable, even if the 2J values indicate less deviation. Meta-GGA functionals provide a better approximation to deal with changes in electron density by including the second derivative of electron density in the exchange-correlation energy. However, the problem of excess electron density delocalization persists, with the best performing functional (TPSS) producing a 2J value of 172.62 cm -1 but with a large spin delocalization of 0.24 µ B Å -3 over the coupler in the triplet state. Hybrid GGA functionals incorporate a fixed fraction of Hatree-Fock (HF) exchange in the exchange-correlation energy, thus reducing the self-interaction errors. The hybrid GGA functional B3LYP predicts a 2J value of 175.02 cm -1 with reduced delocalization of 0.21 µ B Å -3 , an improvement from the GGA and meta-GGA functionals. However, the predicted magnitudes of 2J deviate significantly from the experimental value. The hybrid meta-GGA functionals provide further improvement by including meta-GGA approximation alongside HF exchange. The hybrid meta-GGA functional M06-2X shows excellent localization as the spin density over the coupler is reduced to 0.17 µ B Å -3 . Thus, it predicts a 2J value of 123.04 cm -1 , which is very close to the experimental value. Among all the functionals investigated, the range- Our calculations reveal that a large overestimation in the value of 2J is associated with relatively high spin contamination (Fig. ). The overestimation of 2J values by functionals like BHLYP and LC-PBE despite predicting a good localization of spin density could be attributed to the high degree of spin contamination in their respective BS and triplet states.