For complex 1, the alternating current magnetic susceptibility measurements yield high value of spin reversal barrier i.e., U ef f = 226 cm -1 . The large U ef f value is the result of unquenched orbital angular momentum, thereby, maximizing the magnetic moment. The computed D value from SA-CASSCF calculations is -102.16 cm -1 which further enhances to -109.13 cm -1 when dynamical correlations are taken into account employing NEVPT2.