xy (similar to 2). Since, the first and second excited states are achieved by promoting an electron from d yz to d x 2 -y 2 and d xy respectively with different |m l | states, both of them give a positive contribution to the D value. Hence, the complex exhibits an overall positive D value. Thus, the different splitting pattern due to better π-acceptor imidazoline ylidine than imidazol ylidine (in 2) results in opposite signs of magnetic anisotropy for the two complexes. Another difference between the two molecules is the dihedral angle between the ligands attached to the complexes. Complex 2 renders dihedral angle of 14°in contrast to the large dihedral angle of 70°exhibited by complex 3 (tabulated in Table ). The different dihedral angles can also be the underlying rationale for the contrasting signs of magnetic anisotropy for the complexes 2 and 3 as also observed in Co complexes by Meng et al. The complex 4 is a peculiar case where quasi-degenerate d xy and d x 2 -y 2 are lower in energy as compared to d z 2 . The analysis of molecular orbitals as shown in Figure