Effects of bidentate coordination on the molecular properties rapta-C based complex using theoretical approach.

In this work several quantum properties including the NEDA and QTAIM are computed on three models of rapta-C complexes using DFT with hybrid functional and basis set with ECP and without ECP. Several interesting correlations within the observed properties and also with the reported experimental behaviors of these complexes including their biological activities are presented. The study shows that the stability of the two complexes with bidentate ligands is associated with their high hydrogen bonding stability and existence of stronger non-covalent metal-ligand bonds. The energy decomposition analysis indicated that inter-atomic interactions in the three forms of rapta-C complexes and their stability are governed by the charge transfer term with significant contributions from polarization and electrostatic terms. The higher stability of complex 1 and 2 over 3 comes from the lower exchange repulsion and higher polarization contributions to their stability which agrees perfectly with the experimental observation. Our results provide insight into the nature of intramolecular forces that influence the structural stability of the three complexes.