Publications by authors named "Youssef Arfaoui"

8 Publications

  • Page 1 of 1

Silver-N-heterocyclic carbene complexes-catalyzed multicomponent reactions: Synthesis, spectroscopic characterization, density functional theory calculations, and antibacterial study.

Arch Pharm (Weinheim) 2021 Jun 15:e2100111. Epub 2021 Jun 15.

Research Laboratory of Environmental Sciences and Technologies (LR16ES09), Higher Institute of Environmental Sciences and Technology, University of Carthage, Tunis, Tunisia.

Nowadays, silver-N-heterocyclic carbene (silver-NHCs) complexes are widely used in medicinal chemistry due to their low toxic nature toward humans. Due to the success of silver-NHCs in medicinal applications, interest in these compounds is rapidly increasing. Therefore, the interaction of N,N-disubstituted benzimidazolium salts with Ag O in dichloromethane to prepare novel Ag(I)-NHCs complexes was carried out at room temperature for 120 h in the absence of light. The obtained complexes were identified and characterized by H and C nuclear magnetic resonance, Fourier-transform infrared, UV-Vis, and elemental analysis techniques. Then, the silver complexes were applied for three-component coupling reactions of aldehydes, amines, and alkynes. The effect of changing the alkyl substituent on the NHCs ligand on the catalytic performance was investigated. In addition, it has been found that the complexes are antimicrobially active and show higher activity than the free ligand. The silver-carbene complexes showed antimicrobial activity against specified microorganisms with MIC values between 0.24 and 62.5 μg/ml. These results showed that the silver-NHC complexes exhibit an effective antimicrobial activity against bacterial and fungal strains. A density functional theory calculation study was performed to identify the stability of the obtained complexes. All geometries were optimized employing an effective core potential basis, such as LANL2DZ for the Ag atom and 6-311+G(d,p) for all the other atoms in the gas phase. Electrostatic potential surfaces and LUMO-HOMO energy were computed. Transition energies and excited-state structures were obtained from the time-dependent density functional theory calculations.
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http://dx.doi.org/10.1002/ardp.202100111DOI Listing
June 2021

Regio- and stereoselectivity of the [3+2] cycloaddition of nitrones with methyl-acetophenone: A DFT investigation.

J Mol Graph Model 2021 09 7;107:107960. Epub 2021 Jun 7.

Department of Chemistry, Laboratory of Characterizations, Applications and Modeling of Materials LR18ES08, University of Tunis El Manar, Tunisia. Electronic address:

A theoretical study of the regio- and stereoselectivities of the [3 + 2] cycloaddition reactions of nitrones with substituted alkene (methyl acetophenone) is investigated using density functional theory (DFT) and carried out at B3LYP/6-311+G(d,p) level. The reactivity of these cycloadditions is rationalized by FMO model, activation energy calculations, and philicity indexes. The electronic populations have been calculated from natural orbital, which based on charges by using NBO analysis, MK and CHelpG electrostatic population. The four possible pathways, fused and bridged regioisomeric modes, and the two stereoisomeric approaches endo and exo for the cycloaddition reactions are analyzed and discussed. Analysis of TS geometries and bond lengths demonstrate that these reactions follow a one-step mechanism with asynchronous transition states. The activation energy indicated a favored endo approach along the four reaction pathways.
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http://dx.doi.org/10.1016/j.jmgm.2021.107960DOI Listing
September 2021

DFT investigation of solvent, substituent, and catalysis effects on the intramolecular Diels-Alder reaction.

J Mol Model 2021 Apr 7;27(5):125. Epub 2021 Apr 7.

Department of Chemistry, Laboratory of Characterizations, Applications and Modeling of Materials LR18ES08, University of Tunis El Manar, Tunis, Tunisia.

In this study, we report on a DFT investigation of two intramolecular Diels-Alder furan reactions. Optimizations of the studied structures, TS and IRC calculations, were carried out at B3LYP/6-31G(d) level. We have studied the effect of substituent, solvent and Lewis acid catalyst on cyclization-retrocyclization equilibria, activation energies, and stability of the desired products. The analysis of orbital coefficients, IRC curves, and Wiberg indices have proved that both reactions are under orbital control. We have found that for the reaction I (2↔4 + 5), where R = H, the exo attack is favored by hydrogen bond interaction, while for R = t-Bu, the steric hindrance leads to the endo attack. For the reaction II (3 → 6 + 7), the t-Bu-substituted products are the most stable ones. At another level, we have found that it is recommended to use polar organic solvents as DMSO with Lewis acid catalyst BF. The latest leads to accelerate the reaction II with stabilization of the desired products.
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http://dx.doi.org/10.1007/s00894-021-04729-wDOI Listing
April 2021

Electronic structure and optical properties of isolated and TiO -grafted free base porphyrins for water oxidation: A challenging test case for DFT and TD-DFT.

J Comput Chem 2019 Nov 11;40(29):2530-2538. Epub 2019 Jul 11.

CNRS & Université de Lorraine, Laboratoire de Physique et Chimie Théoriques, Boulevard des Aiguillettes, BP, 70239 54506, Vandoeuvre-lès-Nancy Cedex, France.

Seven free base porphyrins employed in dye-sensitized photoelectrosynthetic cells are investigated with the aim of benchmarking the ability of different density functional theory (DFT) and time-dependent DFT approaches in reproducing their structure, vertical, and E excitation energies and the energy levels alignment (red-ox properties) at the interface with the TiO . We find that both vertical and E excitation energies are accurately reproduced by range-separated functionals, among which the ωB97X-D delivers the lowest absolute deviations from experiments. When the dye/TiO interface is modeled, the physical interfacial energetics is only obtained when the B3LYP functional is employed; on the other hand, M06-2X (54% of exchange) and the two long-range corrected approaches tested (CAM-B3LYP and ωB97X-D) excessively destabilize the semiconductor conduction band levels with respect to the dye's lowest unoccupied molecular orbitals (LUMOs), predicting no pathway for electron injection. © 2019 Wiley Periodicals, Inc.
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http://dx.doi.org/10.1002/jcc.26027DOI Listing
November 2019

Reactivity of pyrazole derivatives with halomethanes: A DFT theoretical study.

J Mol Model 2018 Jul 9;24(8):198. Epub 2018 Jul 9.

Faculty of Sciences, Laboratory of Physical Chemistry of Condensed Materials, University of Tunis El Manar, 2092, Tunis, Tunisia.

The N-alkylation reaction of pyrazole derivatives with halomethanes was studied using density functional theory (DFT). The hybrid method B3LYP was employed, along with an ECP basis set such as LANL2DZ for halogen atoms (X = Cl, Br, I) and the 6-311 + G(d,p) basis set for all other atoms. In order to predict the specific site at which the pyrazole derivatives interact with halomethanes, local reactivity descriptors such as the Fukui functions were calculated. Detailed analysis of transition-state energies showed that alkylation occurred at the nitrogen atom N in the pyrazole derivatives, in agreement with the chemical reactivity results. The reaction mechanisms were elucidated by performing intrinsic reaction coordinate (IRC) calculations that considered the effects of the solvent and the species of halogen in the halomethane.
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http://dx.doi.org/10.1007/s00894-018-3718-4DOI Listing
July 2018

A Short Route to the Ester (±) HomoSarkomycin Johnson-Claisen Rearrangement.

Lett Org Chem 2017 Mar;14(3):181-185

Chemistry Department, College of Science and Arts at Ar Rass, Qassim University, Burayadah 51477, Saudi Arabia.

Background: α-Methylene cycloalkanones are considered of interest because of their biological activity. Herein, in this paper the synthesis of (±) HomoSarkomycine Esters was described and characterized.

Methods: Using Bylis-Hillman adducts, triethlorthoacetate and propanoic acid, (±) HomoSarkomycine Esters could be synthesized by smoothly Johnson-Claisen rearrangement.

Results: A small library of target compounds was prepared under optimized reaction conditions in moderate yields. The reaction mechanism and the DFT study have been investigated.

Conclusion: This methodology provides ready access to 2-hydroxymethyl-2-cyclopentenone 1a which can be served as the raw materials of the synthesis of (±) HomoSarkomycine Ester.
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http://dx.doi.org/10.2174/1570178614666161230123513DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5759048PMC
March 2017

Theoretical investigations on the mechanistic pathway of the thermal rearrangement of substituted N-acyl-2,2-dimethylaziridines.

J Mol Model 2013 Oct 25;19(10):4603-12. Epub 2013 Aug 25.

Laboratoire de Synthèse Organique et Hétérocyclique, Département de Chimie, Faculté des Sciences de Tunis, Université de Tunis El Manar, 2092, El Manar, Tunisie,

The mechanism of the thermal rearrangement of substituted N-acyl-2,2-dimethylaziridines 1 has been studied using quantum chemistry methods. Geometries of reactants, transition states and products have been optimized at the B3LYP/6-311++G(2d,2p) level. Relative energies for various stationary points have been determined and reaction identified by IRC calculations. The results show that thermal rearrangements occur in three ways. Firstly, the transition state TS 1 in which a hydrogen atom of methyl groups migrates from primary carbon to oxygen of amid group to give the N-methallylamide 2. The second is via the transition state TS 2 in which the attack of oxygen to the tertiary carbon yields the oxazoline 3. The third is via the transition state TS 3 in which a hydrogen migrate from the secondary carbon to oxygen to give the vinylamide 4. In order to get insights into the factors determining the exact nature of its interactions with electrophiles, the application of reactivity parameters derived from density functional theory in a local sense, in particular the softness and Fukui function, to interpret and predict the mechanisms of the thermal decomposition of the N-acyl-2,2-dimethylaziridines 1, has been discussed.
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http://dx.doi.org/10.1007/s00894-013-1959-9DOI Listing
October 2013

Ethyl 3-[1-(5,5-dimethyl-2-oxo-1,3,2-dioxaphosphorin-2-yl)propan-2-ylidene]carbazate: a combined X-ray and density functional theory (DFT) study.

Acta Crystallogr C 2010 Jul 10;66(Pt 7):o353-5. Epub 2010 Jun 10.

Laboratoire de Chimie Physique, Faculté des Sciences, El Manar II, 2092 Tunis, Tunisia.

In the title compound, C(11)H(21)N(2)O(5)P, one of the two carbazate N atoms is involved in the C=N double bond and the H atom of the second N atom is engaged in an intramolecular hydrogen bond with an O atom from the dimethylphosphorin-2-yl group, which is in an uncommon cis position with respect to the carbamate group. The cohesion of the crystal structure is also reinforced by weak intermolecular hydrogen bonds. Density functional theory (DFT) calculations at the B3LYP/6-311++g(2d,2p) level revealed the lowest energy structure to have a Z configuration at the C=N bond, which is consistent with the configuration found in the X-ray crystal structure, as well as a less stable E counterpart which lies 2.0 kcal mol(-1) higher in potential energy. Correlations between the experimental and computational studies are discussed.
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http://dx.doi.org/10.1107/S0108270110020688DOI Listing
July 2010
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