To start, we have benchmarked our DFT approach for NiH(CO)3 system which has experimental Aiso= 9 MHz 53 . Our calculated Aiso gives value of 8.81 MHz and is also similar to Aiso= 5.2 MHz reported previously. Next, we found that NiN4 square-planar geometry with constrained HS (〈𝑆〉=1) to have a very high Aiso value ~ 44 MHz, while by definition, (〈𝑆〉=0 system has a zero Aiso value. Using the NiN4C8 model, which is allowed to undergo tetrahedral distortion NiN4 (Figure ), its Aiso value monotonically decreases with decreasing dihedral angle.