Ionic bond in hydrogen transferring of the ferrous and/or ferric human/mouse verdoheme oxygenase.

Formation of five coordinated ferric (ferrous) verdoheme oxygenase complexes have been investigated at ωB97X-D/6-31G(d) level of theory. This process was carried out by adsorption of imidazole and human/mouse verdoheme oxygenase (VO) compounds. Global reactivity indexes show electrophile and nucleophile roles of the VO complexes and Imidazole, respectively. This result confirms their interaction, molecular electrostatic potential (MEP) maps, and low HOMOFRVMO-LUMOImidazole gap. These interactions can cause in adsorption and five coordinated of the VO complexes. More negative value (-64.3 kJ mol-1) of adsorption energy (Eads) in the FRVMO complex shows better adsorption strength and stable configuration. Significant point of this interaction is hydrogen transfer from imidazole to the nearest oxygen of the VO complexes; this issue is approved using quantum theory of atom in molecule (QTAIM) and natural bond orbital (NBO) analysis. QTAIM calculations confirm ionic bonding between the transferred hydrogen and the oxygen atom of the VO. The 312.2-kcal mol-1 s order stabilization energies in this complex are confirmation for strong donation and better formation of five coordinated complex in electron view point.