The QM-only DFT calculations were performed in Gaussian 09 software using UB3LYP/B1 level of theory where B1 is defined as LANL2DZ basis set for Fe atom and 6-31G(d) for all other atoms. The optimized energies were further refined by calculating single-point energy using an all-electron basis set def2-TZVP coupled to UB3LYP. All reported energies are zeropoint energy (ZPE) and Grimme dispersion (G-D3) corrected where ZPE values were obtained from frequency calculation. We optimized the geometry in the gas phase to determine the lowest energy ground state multiplicity followed by a further re-optimization of energetically lowest geometry in chlorobenzene solvent using the SMD solvent model. We chose the chlorobenzene solvent to mimic the non-polar nature of the enzyme environment based on the previous studies. The natural-and spin natural -orbital calculations were carried out to identify the presence of singly occupied molecular orbitals and the nature of the electron spin.