Melek Hajji

University of Kairouan Tunisia
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Heteroleptic cobalt(II) complex with nitrogen-rich macrocycles — Structure, bioactivity and DFT modelling

Abstract

We herein discuss the synthesis and characterization of a novel mononuclear cobalt(II) complex CoII(TPBP)(HTMA)2 with the N-donor ligands; hexamethylenetetramine HTMA and meso-tetrakis[4-(benzoyloxy) phenylporphyrin H2TPBP. Firstly, molecular structure and supramolecular assembly have been thoroughly described. The basic core (porphyrin macrocycle) is nearly planar and the cobalt coordination centre sits in slightly distorted octahedral environment occupied by four pyrrolic nitrogen atoms (NPy) and two HTMA nitrogens (NHTMA). On the basis of quantum chemical density-functional theory calculations, metal—ligand charge-transfer interaction (MLCTI), spin density distribution and chemical reactivity character have been also highlighted. Finally, the bio-activity of free porphyrin and their cobalt complexes was evaluated in vitro, by examining their inhibitory effect against some yeasts and fungal strains, and their ability to scavenge 1,1-diphenyl-picrylhydrazyl DPPH radical. This research could provide rich insights into the structural, electronic and (bio)chemical features of analogues macrocyclic metal complexes.

A newly synthesized nitrogen‐rich derivative of bicyclic quinoxaline—Structural and conceptual DFT reactivity study

Novel nitrogen‐rich compound featured bicyclic quinoxaline as a basic core structure has been synthesized, 1‐{[1‐(3‐azido‐2‐hydroxypropyl)‐1H‐1,2,3‐triazol‐4‐yl]methyl}‐3‐methyl‐1,2‐dihydroquinoxalin‐2‐one with formula C15H16N8O2, and their structural and chemical reactivity aspects have been comprehensively discussed. Nature, role, and relative contribution of weak noncovalent interactions in supramolecular assembly have been assessed through single‐crystal analysis and computational approaches. Useful information about the global and local reactivity were obtained from Conceptual Density Functional Theory at wB97X‐D/cc‐pVDZ level. Studied system could act as strong electrophile and/or moderate nucleophile in polar organic reactions. We hope this study will provide deeper insight in the knowledge of the synthesis and chemistry of the quinoxaline and quinoxaline derivatives.

Synthesis, structure, photophysical properties and biological activity of a cobalt(II) coordination complex with 4,4′-bipyridine and porphyrin chelating ligands

Publication date: Available online 23 March 2019

Source: Journal of Saudi Chemical Society

Author(s): Nesrine Amiri, Sahar Nouir, Melek Hajji, Thierry Roisnel, Taha Guerfel, Gérard Simonneaux, Habib Nasri

Abstract

A new bioactive material of cobalt(II) with 5,10,15,20-tetrakis[4 (benzoyloxy)phenyl] porphyrin (TPBP) and bpy ligands ([CoII(TPBP)(bpy)2] 1) has been synthesized and characterized by Single-crystal X-ray diffraction (SCXRD), spectroscopic methods and quantum-chemistry calculations. In the crystalline structures of six coordinated Co(II) [CoII(TPBP)(bpy)2] 1, linear 1D polymeric chains were observed in which all the porphyrin units are aligned parallel to each other. The crystal packing is stabilized by inter-and intramolecular C–H⋯O and C–H⋯N hydrogen bonds, and by weak C–H⋯Cg π interactions. Interestingly, NBO–Second-order perturbation theory analysis, carried out at the UB3LYP/6-31G(d)/SDD DFT level of theory, demonstrated that a two-center bond between the nitrogen atoms and the cobalt ions (Co) was not found, the Co–Npy/bp interactions are coming from an electronic delocalization between the Npy/Nbp filled orbitals to the anti-bonding LP*(4) and LP*(5) metal NBOs. Mass spectroscopy, and elemental analysis were also investigated to confirm the molecular structure. The downfield shift and the peak broadening of the axial ligand resonances observed in the 1H NMR indicated the contiguity to the paramagnetic Co(II) center. Additionally, the photophysical properties have been evaluated by UV–visible absorption, and fluorescence emission spectroscopies. Finally, bioactivity investigations revealed that free porphyrin TPBP, CoIITPBP and complex 1 could be used as potential antioxidant agents.

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