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,Julius Numbonui Ghogomu,Désiré Bikélé Mama,Elie Younang

doi:10.1155/2017/5237865

Abstract

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.

Highlights

In recent years, the repercussion of free radicals and reactive oxygen species (ROS) in neurodegenerative disorder is more sensitive [1,2,3,4]
We have presented the B3LYP/Mixed I and B3LYP/Mixed II calculations which allowed us to treat the complexation of 3-alkyl-4-phenylacettylamino-4,5-dihydro1h-1,2,4-triazol-5-one derivatives by metal cation (Fe2+, Ni2+, Cu2+, Cu+, and Zn2+)
Our results indicate that the M2+-Oi (i = 2, 3) bond distances yielded by B3LYP/ Mixed II are shorter than those relative to B3LYP/Mixed I due to the poor description of the electron-electron repulsion by this latter

Summary

Introduction

The repercussion of free radicals and reactive oxygen species (ROS) in neurodegenerative disorder is more sensitive [1,2,3,4] The contribution of these ROS to the pathophysiology of myocardial reperfusion damage. Each cell is naturally equipped by defense systems against any destructive effect of ROS This statute of protective mechanism against ROS in humans is attributed to antioxidant molecules [8, 9]. Antioxidant molecules (tocopherol (vitamin E), ascorbic acid (vitamin C), carotenoids, flavonoids, and polyphenols) prevent the proliferation of free radical reactions in all cell membranes. This explains the emergence of studies on the investigation of antioxidant activities of biologically active compounds. This has led to increased pressure on the need for the newer

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