Structural and Antioxidant Properties of Compounds Obtained from Fe2+ Chelation by Juglone and Two of Its Derivatives: DFT, QTAIM, and NBO Studies

Aymard Didier Tamafo Fouegue; Julius Numbonui Ghogomu; Désiré Bikélé Mama; Nyiang Kennet Nkungli; Elie Younang

doi:10.1155/2016/8636409

Structural and Antioxidant Properties of Compounds Obtained from Fe²⁺ Chelation by Juglone and Two of Its Derivatives: DFT, QTAIM, and NBO Studies

Bioinorg Chem Appl. 2016:2016:8636409. doi: 10.1155/2016/8636409. Epub 2016 Sep 28.

Authors

Aymard Didier Tamafo Fouegue¹, Julius Numbonui Ghogomu¹, Désiré Bikélé Mama², Nyiang Kennet Nkungli¹, Elie Younang³

Affiliations

¹ Department of Chemistry, Faculty of Science, University of Dschang, P.O. Box 67, Dschang, Cameroon.
² Department of Chemistry, Faculty of Science, University of Douala, P.O. Box 24157, Douala, Cameroon.
³ Department of Inorganic Chemistry, Faculty of Science, University of Yaoundé I, P.O. Box 812, Yaoundé, Cameroon.

Abstract

The chelating ability of juglone and two of its derivatives towards Fe²⁺ion and the antioxidant activity (AOA) of the resulting chelates and complexes (in the presence of H₂O and CH₃OH as ligands) in gas phase is reported via bond dissociation enthalpy, ionization potential, proton dissociation enthalpy, proton affinity, and electron transfer enthalpy. The DFT/B3LYP level of theory associated with the 6-31+G(d,p) and 6-31G(d) Pople-style basis sets on the atoms of the ligands and the central Fe(II), respectively, was used. Negative chelation free energies obtained revealed that juglone derivatives possessing the O-H substituent (L₂) have the greatest ability to chelate Fe²⁺ ion. Apart from 1B, thermodynamic descriptors of the AOA showed that the direct hydrogen atom transfer is the preferred mechanism of the studied molecules. NBO analysis showed that the Fe-ligand bonds are all formed through metal to ligand charge transfer. QTAIM studies revealed that among all the Fe-ligand bonds, the O₁-Fe bond of 1A is purely covalent. The aforementioned results show that the ligands can be used to fight against Fe(II) toxicity, thus preserving human health, and fight against the deterioration of industrial products. In addition, most of the complexes studied have shown a better AOA than their corresponding ligands.