Initial considerations. In this computational study, all geometries including neutral, oxidized, and reduced species were optimized using two different exchange-correlation functionals that are OLYP and B3LYP. The atom-pairwise dispersion correction with the Becke-Johnson damping scheme (D3BJ) was applied on all optimized geometries. To reduce the computational cost, a model of the TpMePC ligand where used. The phenyl rings of the ligands with their substitutions are replaced by hydrogen atoms. To validate this simplification on the structure parameters, we have firstly compared the main structure parameters of the complex with the full ligand and with the model ligand. Following this validation, we will then present a detailed analysis of the neutral, oxidized, and reduced species using the simplified model of the ligand TpMePC. In the following discussion, we will refer to the simplified complex as M2-Model and M2-Full (M = Re or Os) for the complex with the whole ligand.