Elie YOUNANG

2018Article de revue

The Substitution Effect on Reaction Enthalpies of Antioxidant Mechanisms of Juglone and Its Derivatives in Gas and Solution Phase: DFT Study

Aymard Didier Tamafo Fouégué, Désiré Bikélé Mama, Julius Numbonui Ghogomu, Elie Younang, Marie‐Annie Etoh

Journal of Chemistry

We examined the structure-reaction enthalpies-antioxidant activity relationship of the molecule library built around juglone and its derivatives at B3LYP/6-31+G(d,p) level. Three major antioxidant mechanisms (hydrogen atom transfer (HAT), single electron transfer-proton transfer (SET-PT), and sequential proton loss electron transfer (SPLET)) have been investigated in five solvents and in the gas phase. The delocalization of the unpaired electrons in the radicals or cation radicals has been explored by the natural bond orbital analysis and the interpretation of spin density maps. The results obtained have proven that the HAT mechanism is the thermodynamically preferred mechanism in the gas phase. But, in the solution phase, the SPLET mechanism has been shown to be more predominant than HAT. The reactivity order of compounds towards selected reactive oxygen species has also been studied.

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2017Article de revueAccès ouvert

A DENSITY FUNCTIONAL THEORY INVESTIGATION OF D8 TRANSITION METAL(II) (NI, PD, PT) CHLORIDE COMPLEXES OF SOME VIC-DIOXIMES DERIVATIVES

Ludovid Ngouo Nogheu, Julius Numbonui Ghogomu, Nyiang Kennet Nkungli, Désiré Bikélé Mama, Elie Younang

Physical chemistry research

Herein, a theoretical study on the stability of some vic-dioxime complexes of Ni(II), Pd(II) and Pt(II) in gas and aqueous phases is reported. The DFT/M06/SDD and DFT/M06/6-31G+(d,p) levels of theory were adopted for the metal ions and for every other element respectively. Structural analyses of investigated complexes have revealed square planar geometries stabilized by two O–H⋯Cl hydrogen bonds. Analysis of hydrogen bond energies calculated via quantum theory of atoms in molecules (QTAIM) and computed chemical hardness values has revealed that the stability of the complexes is determined by the hydrogen bond strength. Natural population analysis has revealed ligand-metal charge transfer in the complexes investigated. A good linear agreement with correlation coefficient 0.992 has been found between calculated and experimental IR vibrational frequencies, indicating the validity of the theoretical method employed herein. Negative binding energies obtained are indicative of the stability of the complexes, thus affirming the use of vic-dioximes ligands as potential d8 transition metal eliminating agents in solution.

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2016Article de revue

Structural and Antioxidant Properties of Compounds Obtained from Fe 2+ Chelation by Juglone and Two of Its Derivatives: DFT, QTAIM, and NBO Studies

Aymard Didier Tamafo Fouégué, Julius Numbonui Ghogomu, Désiré Bikélé Mama, Nyiang Kennet Nkungli, Elie Younang

Bioinorganic Chemistry and Applications

The chelating ability of juglone and two of its derivatives towards Fe 2+ ion and the antioxidant activity (AOA) of the resulting chelates and complexes (in the presence of H 2 O and CH 3 OH 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 (L 2 ) have the greatest ability to chelate Fe 2+ 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 O 1 -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.

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1992Article de revue

Ab initio calculations of all‐ trans octatetraene and eight isoelectronic conjugated chains: Semiempirical heats of formation and stabilization energies

Elie Younang, Jean‐Marie André, J. Delhalle

International Journal of Quantum Chemistry

Abstract In the framework of our study of the changes of the electric polarizability upon substituting heteroatomic linkages in conjugated hydrocarbon backbones, we have been led to examine the relative stability of eight compounds isoelectronic to the all‐ trans octatetraene using the Cox and Pilcher concept of stabilization energy ( SE ), SE = Δ H a – Σ N AB E AB , where Δ H a is the heat of atomization of the species under consideration and the E AB 's are bond‐energy terms. Full geometry optimizations at the 4‐31G level have been performed to obtain the equilibrium geometries needed to deduce reliable semiempirical heats of formation from appropriate isodesmic processes. Some of the compounds containing the  CHN and  NN  groups have electric polarizabilities and stabilization energies comparable to octatetrene.

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1991Article de revue

Preliminary theoretical study of acrylonitrile and its methyl derivatives as monomers for cathodic electropolymerization

G. Hennico, J. Delhalle, Elie Younang, Mireille Defranceschi, G. Lécayon, C. Boiziau

International Journal of Quantum Chemistry

Ab initio calculations of the molecular geometry and electronic structure properties (charges, dipole moment, polarizability, HOMO and LUMO energies) of acrylonitrile, CH2CHCN, cis- and trans-2-butenenitrile, CH3CHCHCN, 3-butenenitrile, CH2CHCH2CN, and 2-methyl-2-propenenitrile, CH2C(CH3)CN are obtained at the 3-21G level. Results on three anionic derivatives of these molecules obtained at the 3-21+G level are also reported. Properties of the molecules in their isolated states are considered as a preliminary basis to compare initial steps of bulk and surface polymerization of vinylic monomers by electrochemistry under cathodic polarization.

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1987Article de revue

Ab initio calculations of all-trans octatetraene and some isoelectronic conjugated chains: equilibrium geometry and longitudinal electric polarizability

Elie Younang, Delhalle, Joseph, Andre, Jean-Marie

Digital Access to Libraries (Université catholique de Louvain (UCL), l'Université de Namur (UNamur) and the Université Saint-Louis (USL-B))

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2017Article de revue

A DFT Study of Structural and Bonding Properties of Complexes Obtained from First-Row Transition Metal Chelation by 3-Alkyl-4-phenylacetylamino-4,5-dihydro-1H-1,2,4-triazol-5-one and Its Derivatives

Hubert Jean Nono, Désiré Bikélé Mama, Julius Numbonui Ghogomu, Elie Younang

Bioinorganic Chemistry and Applications

Density functional calculations were used to explore the complexation of 3-alkyl-4-phenylacetylamino-4,5-dihydro-1h-1,2,4-triazol-5-one (ADPHT) derivatives by first-row transition metal cations. Neutral ADPHT ligand and mono deprotonated ligands have been used. Geometry optimizations have been performed in gas-phase and solution-phase (water, benzene, and N,N-dimethylformamide (DMF)) with B3LYP/Mixed I (LanL2DZ for metal atom and 6-31+G(d,p) for C, N, O, and H atoms) and with B3LYP/Mixed II (6-31G(d) for metal atom and 6-31+G(d,p) for C, N, O, and H atoms) especially in the gas-phase. Single points have also been carried out at CCSD(T) level. The B3LYP/Mixed I method was used to calculate thermodynamic energies (energies, enthalpies, and Gibb energies) of the formation of the complexes analyzed. The B3LYP/Mixed I complexation energies in the gas phase are therefore compared to those obtained using B3LYP/Mixed II and CCSD(T) calculations. Our results pointed out that the deprotonation of the ligand increases the binding affinity independently of the metal cation used. The topological parameters yielded from Quantum Theory of Atom in Molecules (QTAIM) indicate that metal-ligand bonds are partly covalent. The significant reduction of the proton affinity (PA) observed when passing from ligands to complexes in gas-phase confirms the notable enhancement of antioxidant activities of neutral ligands.

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2017Article de revue

Quantum Chemical Investigation on the Antioxidant Activity of Neutral and Anionic Forms of Juglone: Metal Chelation and Its Effect on Radical Scavenging Activity

Aymard Didier Tamafo Fouégué, Julius Numbonui Ghogomu, Nyiang Kennet Nkungli, Désiré Bikélé Mama, Elie Younang

Journal of Chemistry

The chelation ability of divalent Mg, Ca, Fe, Co, Ni, Cu, Zn, and monovalent Cu ions by neutral and anionic forms of juglone has been investigated at DFT/B3LYP/6-31+G(d,p) level of theory in gas and aqueous phases. It is noteworthy that only the 1 : 1 stoichiometry was considered herein. The effects of these metals on the radical scavenging activity of neutral juglone were evaluated via the usual descriptors of hydrogen atom transfer. According to our results, metal chelation by the two forms of juglone was spontaneous and exothermic in both media. Based on the binding energies, Cu(II) ion showed the highest affinity for the ligands. QTAIM analyses identified the metal-ligand bonds as intermediate type interactions in all the chelates, except those of Ca and Mg. It was also found that the chelates were better radical scavengers than the ligands. In the gas phase, the scavenging activity of the compounds was found to be governed by direct hydrogen atom transfer, the Co(II) chelate being the most reactive. In the aqueous phase also, the sequential proton loss electron transfer was preferred by all the molecules, while the Cu(II) chelates were the most reactive.

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2016Article de revueAccès ouvert

Structural, Spectral (IR and UV/Visible) and Thermodynamic Properties of Some 3d Transition Metal(II) Chloride Complexes of Glyoxime and Its Derivatives: A DFT and TD-DFT Study

Ludovid Ngouo Nogheu, Julius Numbonui Ghogomu, Désiré Bikélé Mama, Nyiang Kennet Nkungli, Elie Younang, Shridhar R. Gadre

Computational Chemistry

Metal complexes bearing vic-dioxime ligands have been extensively used as analytical and biochemical reagents, and are well-known antimicrobial agents. Herein is reported a DFT study on the molecular structures, thermodynamic properties, chemical reactivity and spectral properties of some 3d metal(II) chloride complexes of glyoxime. The functionals B3LYP and CAM-B3LYP have each been used in conjunction with LANL2DZ for the metal(II) ions (Fe2+, Co2+, Ni2+ and Cu2+) and the Poplestyle basis set 6-31G+(d,p) for the rest of the elements, to perform theoretical calculations. The metal complexation abilities of the glyoxime ligands studied in this work have been evaluated on the basis of metal-ligand binding energies. These ligands were found to have high affinities towards Ni(II) and Fe(II) ions, and all complexation reactions were found to be thermodynamically feasible. Ligand-to-metal electron donations in the complexes studied have been revealed by natural population analysis. The fully optimized geometries of the complexes have adopted square planar structures around the central metal ions. On the basis of orbital composition analysis, the UV-Vis electronic absorption bands of these molecules have been attributed mainly to MLCT, LMCT and d-d electronic transitions involving metal-based orbitals.

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2016Article de revueAccès ouvert

Thermodynamics-antioxidant activity relationships of some 4-benzylidenamino-4, 5-dihydro-1h-1,2,4-triazol-5-one derivatives: Theoretical evaluation

Joseph Zobo Mfomo, Désiré Bikélé Mama, Daniel Lissouck, Elie Younang, S. Nsikabaka, Ibrahim Mbouombouo Ndassa et 1 autre(s)

International Journal of Food Properties

Density functional methods were used to predict the antioxidative efficiency of thirteen 4-benzylidenamino-4, 5-dihydro-1H-1,2,4-triazol-5-one derivatives in the gas phase and in the solution phase (water and benzene). Optimized geometries of molecules and reaction thermodynamic energies (enthalpies and reaction-free energies) of three main antioxidant mechanisms (hydrogen atom transfer, single electron transfer-proton transfer, and sequential proton loss electron transfer) were studied at B3LYP/6-31G (d,p) level. Solvent contributions to thermodynamic energies were computed employing integral equation formalism integral equation formalism polarized continuum model method. Obtained results revealed that the three main working mechanisms were endothermic, but not spontaneous especially in the gas phase. We found that the single electron transfer process from the anionic form was more preferable than that from the neutral form in the gas phase. The comparison of the ionization potentials of 4-benzylidenamino-4, 5-dihydro-1H-1,2,4-triazol-5-one derivatives to those of classical antioxidants (gallic acid, caffeic acid, ferulic acid, and ascorbic acid) indicated that the electron transfer mechanism was more predominant in the thirteen 4-benzylidenamino-4, 5-dihydro-1H-1,2,4-triazol-5-one derivative compounds. Thermodynamically, single electron transfer process from the anionic form was the most preferable mechanism in the gas phase. Solvent effect drastically modified thermodynamic energies of mechanisms. The proton transfer process was the thermodynamically favored mechanism as compared to other mechanisms in both solvents. It is worth mentioning that all the mechanisms were found not to be spontaneous in the solution phase except the proton transfer process.

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Elie YOUNANG

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Publications

2018

The Substitution Effect on Reaction Enthalpies of Antioxidant Mechanisms of Juglone and Its Derivatives in Gas and Solution Phase: DFT Study

2017

A DENSITY FUNCTIONAL THEORY INVESTIGATION OF D8 TRANSITION METAL(II) (NI, PD, PT) CHLORIDE COMPLEXES OF SOME VIC-DIOXIMES DERIVATIVES

2016

Structural and Antioxidant Properties of Compounds Obtained from Fe 2+ Chelation by Juglone and Two of Its Derivatives: DFT, QTAIM, and NBO Studies

2015

DFT Investigation of Chelation of Divalent Cations by Some 4-Benzylidenamino-4,5-Dihydro-1H-1,2,4-Triazol-5-One Derivatives

1992

Ab initio calculations of all‐ trans octatetraene and eight isoelectronic conjugated chains: Semiempirical heats of formation and stabilization energies

Prospective theoretical and experimental study towards electrochemically grafted poly(N-vinyl-2-pyrrolidone) films on metallic surfaces

1991

Preliminary theoretical study of acrylonitrile and its methyl derivatives as monomers for cathodic electropolymerization

1987

Ab initio calculations of all-trans octatetraene and some isoelectronic conjugated chains: equilibrium geometry and longitudinal electric polarizability

Heats of formation of some small molecules and radicals

A DFT Study of Structural and Bonding Properties of Complexes Obtained from First-Row Transition Metal Chelation by 3-Alkyl-4-phenylacetylamino-4,5-dihydro-1H-1,2,4-triazol-5-one and Its Derivatives

Quantum Chemical Investigation on the Antioxidant Activity of Neutral and Anionic Forms of Juglone: Metal Chelation and Its Effect on Radical Scavenging Activity

Structural, Spectral (IR and UV/Visible) and Thermodynamic Properties of Some 3d Transition Metal(II) Chloride Complexes of Glyoxime and Its Derivatives: A DFT and TD-DFT Study

Thermodynamics-antioxidant activity relationships of some 4-benzylidenamino-4, 5-dihydro-1h-1,2,4-triazol-5-one derivatives: Theoretical evaluation

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