Publications by authors named "Mohamed Hagar"

20 Publications

  • Page 1 of 1

Design, Synthesis, Molecular Modeling, Anticancer Studies, and Density Functional Theory Calculations of 4-(1,2,4-Triazol-3-ylsulfanylmethyl)-1,2,3-triazole Derivatives.

ACS Omega 2021 Jan 31;6(1):301-316. Epub 2020 Dec 31.

Chemistry Department, College of Sciences, Yanbu, Taibah University, Yanbu 30799, Saudi Arabia.

New conjugates of substituted 1,2,3-triazoles linked to 1,2,4-triazoles were synthesized starting from the appropriate S-propargylated 1,2,4-triazoles and . Ligation of 1,2,4-triazoles to the 1,2,3-triazole core was performed through Cu(I)-catalyzed cycloaddition of 1,2,4-triazole-based alkyne side chain and/or with several un/functionalized alkyl- and/or aryl-substituted azides to afford the desired 1,4-disubstituted 1,2,3-triazoles , using both classical and microwave methods. After their spectroscopic characterization (infrared, H, C nuclear magnetic resonance, and elemental analyses), an anticancer screening was carried out against some cancer cell lines including human colon carcinoma (Caco-2 and HCT116), human cervical carcinoma (HeLa), and human breast adenocarcinoma (MCF-7). The outcomes of this exploration revealed that compounds , , and had a significant anticancer activity against MCF-7 and Caco-2 cancer cell lines with IC values of 0.31 and 4.98 μM, respectively, in relation to the standard reference drug, doxorubicin. Enzyme-docking examination was executed onto cyclin-dependent kinase 2; a promising aim for cancer medication. Synthesized compounds acquiring highest potency showcased superior interactions with the active site residue of the target protein and exhibited minimum binding energy. Finally, the density functional theory (DFT) calculations were carried out to confirm the outcomes of the molecular docking and the experimental findings. The chemical reactivity descriptors such as softness (δ), global hardness (η), electronegativity (χ), and electrophilicity were calculated from the levels of the predicted frontier molecular orbitals and their energy gap. The DFT results and the molecular docking calculation results explained the activity of the most expectedly active compounds , , and .
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http://dx.doi.org/10.1021/acsomega.0c04595DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7807778PMC
January 2021

Deep Learning for Accelerometric Data Assessment and Ataxic Gait Monitoring.

IEEE Trans Neural Syst Rehabil Eng 2021 2;29:360-367. Epub 2021 Mar 2.

Ataxic gait monitoring and assessment of neurological disorders belong to important multidisciplinary areas that are supported by digital signal processing methods and machine learning tools. This paper presents the possibility of using accelerometric data to optimise deep learning convolutional neural network systems to distinguish between ataxic and normal gait. The experimental dataset includes 860 signal segments of 16 ataxic patients and 19 individuals from the control set with the mean age of 38.6 and 39.6 years, respectively. The proposed methodology is based upon the analysis of frequency components of accelerometric signals simultaneously recorded at specific body positions with a sampling frequency of 60 Hz. The deep learning system uses all of the frequency components in a range of 〈0,30 〉 Hz. Our classification results are compared with those obtained by standard methods, which include the support vector machine, Bayesian methods, and the two-layer neural network with features estimated as the relative power in selected frequency bands. Our results show that the appropriate selection of sensor positions can increase the accuracy from 81.2% for the foot position to 91.7% for the spine position. Combining the input data and the deep learning methodology with five layers increased the accuracy to 95.8%. Our methodology suggests that artificial intelligence methods and deep learning are efficient methods in the assessment of motion disorders and they have a wide range of further applications.
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http://dx.doi.org/10.1109/TNSRE.2021.3051093DOI Listing
March 2021

Experimental and Computational Approaches of Newly Polymorphic Supramolecular -Bonded Liquid Crystal Complexes.

Front Chem 2020 2;8:571120. Epub 2020 Nov 2.

Department of Chemistry, Faculty of Science, Cairo University, Cairo, Egypt.

New 1:2 liquid crystalline supramolecular H-bonded complexes (SMHBCs) were synthesized through double H-bond interactions between 4-(nicotinoyloxy) phenyl nicotinate as the base component and two molecules of 4-n-alkoxybenzoic acid (An). The base component was expected to be in two conformers according to the orientation of the N atom and the carboxylate group, conformer () and -conformer (). DFT calculations revealed that only one of the two possible conformers of exists, and the addition of the two molecules of the alkoxy acids () did not affect its conformation. The mesomorphic properties of all of the prepared complexes (/), bearing different terminal flexible alkoxy chains were investigated, and the formation of the H-bonds were confirmed by differential scanning calorimetry (DSC), and the phases were identified by polarized optical microscopy (POM), and FT-IR spectroscopy. Highly thermally stable mesophases possessing broad temperature ranges were observed for all investigated complexes compared to their individual components. Depending on the length of the terminal flexible alkoxy chain, the prepared SMHBCs were shown to exhibit di- or tri-morphic enantiotropic mesophases. The effect of replacing one of the -COO- connecting units by an azo group (-N=N-) in the basic molecule (), on the mesomorphic properties has been investigated experimentally ( DSC) and theoretically ( DFT). The DFT calculations revealed that the polarizability, the dipole moment, and the aspect ratio of the investigated SMHBCs are lower than those of their corresponding ester/azo analogs. All these factors rationalize the enhanced smectic mesophase ranges of the complexes compared with those of the ester/azo analogs. The high aspect ratios and dipole moments of the SMHBCs of the azo derivative enforces the lateral intermolecular attraction that permits the formation of the more ordered smectic C mesophase with respect to the enhanced polymorphic mesophases of the diester derivative.
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http://dx.doi.org/10.3389/fchem.2020.571120DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7667271PMC
November 2020

Investigation of Some Antiviral -Heterocycles as COVID 19 Drug: Molecular Docking and DFT Calculations.

Int J Mol Sci 2020 May 30;21(11). Epub 2020 May 30.

Chemistry Department, College of Sciences, Al-Madina Al-Munawarah, Taibah University, Al-Madina 30002, Saudi Arabia.

The novel coronavirus, COVID-19, caused by SARS-CoV-2, is a global health pandemic that started in December 2019. The effective drug target among coronaviruses is the main protease M, because of its essential role in processing the polyproteins that are translated from the viral RNA. In this study, the bioactivity of some selected heterocyclic drugs named Favipiravir (), Amodiaquine (), 2'-Fluoro-2'-deoxycytidine (), and Ribavirin () was evaluated as inhibitors and nucleotide analogues for COVID-19 using computational modeling strategies. The density functional theory (DFT) calculations were performed to estimate the thermal parameters, dipole moment, polarizability, and molecular electrostatic potential of the present drugs; additionally, Mulliken atomic charges of the drugs as well as the chemical reactivity descriptors were investigated. The nominated drugs were docked on SARS-CoV-2 main protease (PDB: 6LU7) to evaluate the binding affinity of these drugs. Besides, the computations data of DFT the docking simulation studies was predicted that the Amodiaquine () has the least binding energy (-7.77 Kcal/mol) and might serve as a good inhibitor to SARS-CoV-2 comparable with the approved medicines, hydroxychloroquine, and remdesivir which have binding affinity -6.06 and -4.96 Kcal/mol, respectively. The high binding affinity of was attributed to the presence of three hydrogen bonds along with different hydrophobic interactions between the drug and the critical amino acids residues of the receptor. Finally, the estimated molecular electrostatic potential results by DFT were used to illustrate the molecular docking findings. The DFT calculations showed that drug has the highest of lying HOMO, electrophilicity index, basicity, and dipole moment. All these parameters could share with different extent to significantly affect the binding affinity of these drugs with the active protein sites.
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http://dx.doi.org/10.3390/ijms21113922DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7312990PMC
May 2020

Induced Wide Nematic Phase by Seven-Ring Supramolecular H-Bonded Systems: Experimental and Computational Evaluation.

Molecules 2020 Apr 7;25(7). Epub 2020 Apr 7.

Chemistry Department, College of Sciences, Yanbu, Taibah University, Yanbu 30799, Saudi Arabia.

New seven-ring systems of dipyridine derivative liquid crystalline 2:1 supramolecular H-bonded complexes were formed between 4-n-alkoxyphenylazo benzoic acids and 4-(2-(pyridin-4-yl)diazenyl)phenyl nicotinate. Mesomorphic behaviors of the prepared complexes were investigated using a combination of differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). Fermi bands attributed to the presence of intermolecular H-bond interactions were confirmed by FT-IR spectroscopy. All prepared complexes possessed an enantiotropic nematic phase with a broad temperature nematogenic range. Phases were confirmed by miscibility with a standard nematic (N) compound. A comparison was constructed to investigate the influence of the incorporation of the azophenyl moiety on the mesomeric behavior of corresponding five-membered complexes. It was found that the present complexes observed induced a wide nematic phase with relatively higher temperature ranges than the five aromatic systems. Density functional theory (DFT ) suggested the nonlinear geometry of the formed complex. The results of the DFT explained the nematic mesophase formation. Moreover, the π-π stacking of the aromatic moiety in the phenylazo acid plays an effective role in the mesomorphic thermal stability. The energy difference between the frontier molecular orbitals, HOMO (highest occupied) and LUMO (lowest occupied), and the molecular electrostatic potential (MEP) of the prepared complexes were estimated by DFT calculations. The results were used to illustrate the observed nematic phase for all H-bonded supramolecular complexes. Finally, photophysical studies were discussed which were carried out by UV spectroscopy connected to a hot stage.
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http://dx.doi.org/10.3390/molecules25071694DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7180779PMC
April 2020

New Symmetrical U- and Wavy-Shaped Supramolecular H-Bonded Systems; Geometrical and Mesomorphic Approaches.

Molecules 2020 Mar 20;25(6). Epub 2020 Mar 20.

Chemistry Department, College of Sciences, Al-Madina Al-Munawarah, Taibah University, Al-Madina 30002, Saudi Arabia.

New mesomorphic symmetrical 2:1 supramolecular H-bonded complexes of seven phenyl rings were prepared between 4-n-alkoxyphenylazobenzoic acids and 4-(2-(pyridin-3-yl)diazenyl)phenyl nicotinate. Mesomorphic studies of the prepared complexes were investigated using differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). Fermi bands of the formed H-bonded interactions were confirmed by FT-IR spectroscopy. Geometrical parameters for all complexes were performed using the density functional theory (DFT) calculations method. Theoretical results revealed that the prepared H-bonded complexes are in non-linear geometry with U-shaped and wavy-shaped geometrical structures; however, the greater linearity of the wavy-shaped compounds could be the reason for their stability with respect to the U-shaped conformer. Moreover, the stable, wavy shape of supramolecular H-bonded complexes (SMHBCs) has been used to illustrate mesomeric behavior in terms of the molecular interaction. The experimental mesomorphic investigations revealed that all complexes possess enantiotropic smectic C phase. Phases were confirmed by miscibility with a standard smectic C (SmC) compound. A comparison was constructed to investigate the effect of incorporating azophenyl moiety into the mesomeric behavior of the corresponding five-membered complexes. It was found that the addition of the extra phenylazo group to the acid moiety has a great increment of the mesophase stability () values with respect to the monotropic SmC phase of the five aromatic systems to the high stable enantiotropic SmC mesophase.
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http://dx.doi.org/10.3390/molecules25061420DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7144929PMC
March 2020

Induced Phases of New H-bonded Supramolecular Liquid Crystal Complexes; Mesomorphic and Geometrical Estimation.

Molecules 2020 Mar 28;25(7). Epub 2020 Mar 28.

Chemistry Department, College of Sciences, Taibah University, Yanbu 30799, Saudi Arabia.

New five rings architecture of 1:1 supramolecular hydrogen bonded (H-bonded) complexes were formed between 4-(2-(pyridin-4-yl)diazenyl-3-methylphenyl 4-alkoxybenzoates and 4-n-alkoxyphenyliminobenzoic acids. Mesomorphic and optical behaviors of three systems designed complexes were investigated by differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). H-bonded interactions were confirmed via FT-IR spectroscopy. Computational calculations were carried out by density functional theory (DFT) estimation for all formed complexes. Experimental evaluations were correlated with the theoretical predictions and results revealed that, all prepared complexes possessing enantiotropic tri-mesophases with induced smectic C (SmC) and nematic temperature ranges. Moreover, DFT predicted for all formed supramolecular complexes possessing a non-linear bent geometry. Moreover, the π-π stacking of the aromatic rings plays an important role in the mesomorphic properties and thermal stabilities of observed phases. The energy changes between frontier molecular orbitals (HOMO and LUMO) and the molecular electrostatic potential (MEP) of the designed complexes were discussed and related to the experimental results.
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http://dx.doi.org/10.3390/molecules25071549DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7180916PMC
March 2020

Chair- and V-Shaped of H-bonded Supramolecular Complexes of Azophenyl Nicotinate Derivatives; Mesomorphic and DFT Molecular Geometry Aspects.

Molecules 2020 Mar 26;25(7). Epub 2020 Mar 26.

Faculty of Science, Department of Chemistry, Cairo University, Cairo 12613, Egypt.

New geometrical architectures of chair- and V-shaped supramolecular liquid crystalline complexes were molded through 1:1 intermolecular hydrogen bonding interactions between 4-(4-(hexyloxy)phenylazo)methyl)phenyl nicotinate and 4-alkoxybenzoic acids. The length of terminal alkoxy acid chains varied, = 6 to 16 carbons. The mesomorphic behaviour of these complexes was examined through differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). Fourier-transform infrared spectroscopy (FT-IR) was carried out to confirm the presence of Fermi bands that appeared for the hydrogen bonding formation. Enantiotropic nematic phases were observed and covered all lengths of alkoxy chains. The geometrical structures of the prepared supramolecular complexes geometries were estimated by Density functional theory (DFT) calculations. The supramolecular complexes are projected to exhibit a nonlinear geometry with V-shaped and chair-shaped geometry. The chair-shaped conformers of were found to be more stable than V-shaped isomeric complexes. Moreover, the effect of the change of the mesogenic core on the mesophase thermal stability () has been investigated by a comparative study of the present azo supramolecular H-bonding LCs (SMHBCs) and our previously reported their Schiff base analogue complexes, . The findings of the DFT illustrated the high impact of CH=N as a mesogenic core on the mesomorphic behavior in terms of the competitive lateral and terminal intermolecular interactions as well as the molecular electrostatic potential (MEP).
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http://dx.doi.org/10.3390/molecules25071510DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7181272PMC
March 2020

Synthesis, Optical, and Geometrical Approaches of New Natural Fatty Acids' Esters/Schiff Base Liquid Crystals.

Molecules 2019 Nov 25;24(23). Epub 2019 Nov 25.

College of Sciences, Chemistry Department, Taibah University, Yanbu 30799, Saudi Arabia.

Schiff base liquid crystals, known as [4-(hexyloxy)phenylimino)methyl]phenyl palmitate (), [4-(hexyloxy)phenylimino)methyl]phenyl oleate () and [4-(hexyloxy)phenylimino)methyl]phenyl linoleate (, were synthesized from palmitic, oleic, and linoleic natural fatty acids. The prepared compounds have been investigated for their thermal and optical behavior as well as phase formation using differential scanning calorimetry (DSC) and polarized optical microscopy (POM). Molecular structures of all studied compounds were confirmed via elemental analysis, FT-IR, H NMR, and C NMR. Smectic phase is the observed mesophase for all compounds; however, their type and range depend upon the terminal alkanoate chains attached to the phenyl ring. Computational calculations, Density functional theory (DFT), energy difference of the frontier molecular orbital (FMOs), as well as the thermodynamic parameters of different molecular configurations isomers were discussed. It was found that the mesophase behavior and the geometrical characteristics were affected by the degree of unsaturation of fatty terminal chains. Furthermore, the geometrical structure of the CH=N linkage plays an important role in the thermal stability and optical transition temperature.
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http://dx.doi.org/10.3390/molecules24234293DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6930458PMC
November 2019

The Synthesis of New Thermal Stable Schiff Base/Ester Liquid Crystals: A Computational, Mesomorphic, and Optical Study.

Molecules 2019 Aug 21;24(17). Epub 2019 Aug 21.

Physics Department, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia.

A Schiff base supramolecular 4-[(4-(hexyloxy)phenylimino)methyl]benzoic acid and a new series of Schiff base/ester linkages named 4-substitutedphenyl 4-[(4-(hexyloxy)phenylimino)methyl]benzoate liquid crystals were synthesized. The thermal stability, mesomorphic, and optical behavior of the prepared compounds were characterized by differential scanning calorimetry (DSC), Thermogravemetric analysis (TGA), polarized optical microscopy (POM), and UV spectroscopy. FT-IR, H-NMR, C-NMR, and elemental analyses were carried out to elucidate and confirm the molecular structures of the synthesized compounds. The investigated series comprising different sized terminal polar groups changed between CH(CH), H, I, and F. It was found that the supramolecular imino acid dimer is enantiotropic dimorphic, with a wide SmA phase and a good N phase range. The other series of terminally substituted Schiff base/esters are mesomorphic with a high thermal stable SmA phase, except the iodo derivative, which showed dimorphic SmA and N phases. The effect of the position and the orientation of the cores, as well as the terminal substituent of the type and the stability of the mesophase, were studied. A computational theoretical study of the effects of the van der Waal's volume, the Hammett substituent coefficient, the inductive sigma constant, and other geometrical parameters were discussed. The study revealed that the planarity of the two phenyl rings attached with an imino linking group impacted the resonance effect of the terminal substituents rather than their inductive effect. A detailed study on the effect of the estimated thermal parameters, as well as their geometrical planarity with the type and stability of the formed mesophase, was discussed.
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http://dx.doi.org/10.3390/molecules24173032DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6749398PMC
August 2019

Synthesis and evaluation of antibacterial and antibiofilm activities of pyridin-2-yl hexanoate.

Microb Pathog 2018 Dec 13;125:205-209. Epub 2018 Sep 13.

Laboratory of Analysis, Treatment and Valorization of Pollutants of the Environment and Products, Faculty of Pharmacy, Monastir University, Tunisia.

Synthesized Pyridin-2-yl hexanoate was screened for its antibacterial and antibiofilm activities using the broth microdilution method and XTT assay respectively. The obtained results revealed that synthesized molecule inhibited the growth of pathogenic bacteria (MICs value ranged from 80 to 640 μg ml). Moreover, it induced a strong antibiofilm effect against Gram positive cocci (BIC was 366, 378 and 412 μg ml for Streptococcus mutans ATCC 25175, Streptococcus salivarius ATCC 13419 and Streptococcus oralis ATCC 6249 respectively). Basis on these results, pyridin-2-yl hexanoate may be considered as effective compound with antibacterial and antibiofilm activities.
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http://dx.doi.org/10.1016/j.micpath.2018.09.022DOI Listing
December 2018

Effect of GO nanosheets on spectrophotometric determination of tyrosine in urine and serum using nitrosonaphthol.

Anal Biochem 2018 10 1;558:12-18. Epub 2018 Aug 1.

Chemistry Department, Faculty of Science at Yanbu, Taibah University, Yanbu 46423, Saudi Arabia; Environmental Biotechnology Department, Genetic Engineering and Biotechnology Research Institute, University of Sadat City, Sadat City 32897, Egypt. Electronic address:

Here, we aimed to use graphene oxide to improve the selectivity and sensitivity of Tyr determination via the reaction with 1-nitroso-2-naphthol as a selective reagent of Tyr. The reaction between Tyr and 1-nitroso-2-naphthol in absence and presence of GO was studied spectrophotometrically. Different parameters such as concentrations, temperature, incubation time were optimized. The obtained data showed that the maximum absorbance was achieved by using 2 mL of 0.03% 1-nitroso-2-naphthol at temperature 60 °C for 10 min. On the basis of calibration curve of various concentrations of Tyr in the presence of 20 μg mL GO, the limit of detection was 6.4 × 10 M (1.15 μg mL), where in absence of GO was 1.1 × 10 M (19.9 μg mL). The selectivity of Tyr in presence of other amino acids and phenols was studied with and without GO. The data obtained revealed that the selectivity of Tyr in presence of GO with respect to some amino acids and phenols was improved. The proposed method has been applied for the determination of Tyr in urine and serum samples. Therefore, GO is a powerful catalytic surface for the sensitive and selective determination of Try in biological fluids.
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http://dx.doi.org/10.1016/j.ab.2018.07.024DOI Listing
October 2018

Ball Milling Promoted -Heterocycles Synthesis.

Molecules 2018 Jun 4;23(6). Epub 2018 Jun 4.

Chemistry Department, Faculty of Science, Taibah University, Yanbu 46423 Saudi Arabia.

In the last years, numerous protocols have been published using ball milling for organic synthesis. Compared to other methods such as microwave or ultrasound irradiation and ionic liquids, ball mill chemistry is an economical, and ecofriendly method in organic synthesis that is rather underrepresented in the knowledge of organic chemists. The aim of this review is to explore the advantages of the application of ball milling in synthesis of -heterocyclic compounds.
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http://dx.doi.org/10.3390/molecules23061348DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6100593PMC
June 2018

Nanotransition Materials (NTMs): Photocatalysis, Validated High Effective Sorbent Models Study for Organic Dye Degradation and Precise Mathematical Data's at Standardized Level.

Nanomaterials (Basel) 2018 Feb 27;8(3). Epub 2018 Feb 27.

Saraswati Devi Post Graduate College, Khadda Bazar, Kushinagar UP 274802, India.

The present work describes the synthesis of copper oxide nanoparticles (CuONPs) via a solution process with the aim of applying the nano-adsorbent for the reduction of methylene blue (MB) dye in alkaline media. These NPs were characterized via Field emission scanning electron microscopy (FE-SEM), X-ray diffraction, high-resolution Transmission electron microscopy (TEM), and ultra violet UV-visible spectroscopy to confirm their morphology and crystalline and optical properties in order to design an adsorption-degradation process. The photocatalytic CuONPs exhibited dynamic properties, great adsorption affinity during the chemisorption process, and operated at various modes with a strong interaction between the adsorbent and the adsorptive species, and equilibrium isotherm, kinetic isotherm, and thermodynamic activities in the presence of UV light. All basic quantities, such as concentration, pH, adsorbent dose, time, and temperature, were determined by an optimization process. The best-fitted adsorption Langmuir model (² = 0.9988) and performance, including adsorption capacity (350.87 mg/g), photocatalytic efficiency (90.74%), and degradation rate constant (s = 2.23 ×10 min), illustrate good feasibility with respect to sorption-reduction reactions but followed a pseudo-second-order kinetic on the adsorbent surface, reaching an equilibrium point in 80 min. The thermodynamic analysis suggests that the adsorption reaction is spontaneous and endothermic in nature. The thermodynamic parameters such as enthalpy (∆H°), entropy (∆S°), and Gibbs free energy (∆G°) give effective results to support a chemical reduction reaction at 303 K temperature. The equilibrium isotherm and kinetic and thermodynamic models with error function analysis explore the potential, acceptability, accuracy, access to adsorbents, and novelty of an unrivaled-sorption system.
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http://dx.doi.org/10.3390/nano8030134DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5869625PMC
February 2018

Uptake of Tyrosine Amino Acid on Nano-Graphene Oxide.

Materials (Basel) 2018 Jan 4;11(1). Epub 2018 Jan 4.

Chemistry Department, Faculty of Science at Yanbu, Taibah University, Yanbu 46423, Saudi Arabia.

Graphene oxide (GO) is emerging as a promising nanomaterial with potential application in the detection and analysis of amino acids, DNA, enzymes, and proteins in biological fluid samples. So, the reaction of GO with amino acids should be characterized and determined before using it in biosensing methods and devices. In this study, the reaction of tyrosine amino acid (Tyr) with GO was characterized using FT-IR, UV-vis spectrophotometry, and scanning electron microscopy (SEM) before its use. The optimum conditions for GO's interaction with Tyr amino acid have been studied under variable conditions. The optimum conditions of pH, temperature, shaking time, and GO and tyrosine concentrations for the uptaking of tyrosine amino acid onto the GO's surface from aqueous solution were determined. The SEM analysis showed that the GO supplied was in a particle size range between 5.4 and 8.1 nm. A pH of 8.4-9.4 at 25 °C and 5 min of shaking time were the optimum conditions for a maximum uptake of 1.4 μg/mL of tyrosine amino acid onto 0.2 mg/mL of GO.
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http://dx.doi.org/10.3390/ma11010068DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5793566PMC
January 2018

Ball Milling Assisted Solvent and Catalyst Free Synthesis of Benzimidazoles and Their Derivatives.

Molecules 2016 Aug 24;21(9). Epub 2016 Aug 24.

Faculty of Science, Chemistry Department, Yanbu, Taibah University, Yanbu, Saudi Arabia.

Benzoic acid and o-phenylenediamine efficiently reacted under the green solvent-free Ball Milling method. Several reaction parameters were investigated such as rotation frequency; milling balls weight and milling time. The optimum reaction condition was milling with 56.6 g weight of balls at 20 Hz frequency for one hour milling time. The study was extended for synthesis of a series of benzimidazol-2-one or benzimidazol-2-thione using different aldehydes; carboxylic acids; urea; thiourea or ammonium thiocyanate with o-phenylenediamine. Moreover; the alkylation of benzimidazolone or benzimidazolthione using ethyl chloroacetate was also studied.
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http://dx.doi.org/10.3390/molecules21091111DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6274055PMC
August 2016

Ultrasonic Synthesis, Molecular Structure and Mechanistic Study of 1,3-Dipolar Cycloaddition Reaction of 1-Alkynylpyridinium-3-olate and Acetylene Derivatives.

Molecules 2016 Jun 29;21(7). Epub 2016 Jun 29.

Department of Chemistry, Faculty of Science, Alexandria University, P. O. Box 426, Ibrahimia, Alexandria 21321, Egypt.

Regioselectively, ethyl propiolate reacted with 1-(propergyl)-pyridinium-3-olate to give two regioisomers; ethyl 4-oxo-8-(prop-2-ynyl)-8-aza-bicyclo(3.2.1)octa-2,6-diene-6-carboxylate 4, ethyl 2-oxo-8-(prop-2-ynyl)-8-aza-bicyclo(3.2.1)octa-3,6-diene-6-carboxylate 5 as well as ethyl 2,6-dihydro-6-(prop-2-ynyl)furo(2,3-c)pyridine-3-carboxylate 6. The obtained compounds were identified by their spectral (IR, mass and NMR) data. Moreover, DFT quantum chemical calculations were used to study the mechanism of the cycloaddition reaction. The regioselectivity was explained using transition state calculations, where the calculations agreed with the formation of products 4 and 5 in almost the same ratio. The reaction was also extended for diphenylaceylene as dipolarophile to give only two products instead of three.
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http://dx.doi.org/10.3390/molecules21070848DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6274580PMC
June 2016

Experimental and theoretical spectroscopic studies, HOMO-LUMO, NBO analyses and thione-thiol tautomerism of a new hybrid of 1,3,4-oxadiazole-thione with quinazolin-4-one.

Spectrochim Acta A Mol Biomol Spectrosc 2015 Jun 2;145:270-279. Epub 2015 Feb 2.

Chemistry Department, Faculty of Science, Alexandria University, Alexandria 21321, Egypt. Electronic address:

The hybrid 3-(4-chlorophenyl)-2-[(5-thioxo-4,5-dihydro-1,3,4-oxadiazol-2-yl)methylthio]quinazolin-4(3H)-one has been synthesized and characterized using elemental analysis, FTIR and NMR spectroscopy. The thione-thiol tautomeric equilibria has been studied using both DFT/B3LYP and HF methods at different basis sets. The results of calculations showed predominance of the thione form. The molecular structure and vibrational spectra of the stable tautomer are predicted using the same level of theory. The complete assignments of the vibrational modes were performed on the basis of potential energy distribution (PED). The 6-311++G(d,p) gave the best results compared to the experimental data. The chemical shift values of the two tautomers are calculated using GIAO method. The NH proton of the thione tautomer have chemical shift value closer to the experimental data compared to the SH proton of the thiol one. The electronic transitions are predicted using the TD-DFT calculations at B3LYP/6-311++G(d,p) level of theory. The calculated polarizability and first hyperpolarizability showed that the studied compound has better NLO properties than urea. The molecular electrostatic potential (MEP) analysis reveals the sites for electrophilic and nucleophilic attack in the molecule. NBO analysis is carried out to investigate the stabilization energy of various intramolecular charge transfer interactions within the studied molecule.
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http://dx.doi.org/10.1016/j.saa.2015.01.061DOI Listing
June 2015

Catalyst activity or stability: the dilemma in Pd-catalyzed polyketone synthesis.

Dalton Trans 2013 Oct;42(40):14583-602

Dipartimento di Scienze Chimiche e Farmaceutiche, Università di Trieste, Via Licio Giorgieri 1, 34127 Trieste, Italy.

A series of Pd-complexes containing nonsymmetrical bis(aryl-imino)acenaphthene (Ar-BIAN) ligands, characterized by substituents on the meta positions of the aryl rings, have been synthesized, characterized and applied in CO/vinyl arene copolymerization reactions. Crystal structures of two neutral Pd-complexes have been solved allowing comparison of the bonding properties of the ligand. Kinetic and mechanistic investigations on these complexes have been performed. The kinetic investigations indicate that in general ligands with electron-withdrawing substituents give more active, but less stable, catalytic systems, although steric effects also play a role. The good performance observed with nonsymmetrical ligands is at least in part due to a compromise between catalyst activity and lifetime, leading to a higher overall productivity with respect to catalysts based on their symmetrical counterparts. Additionally, careful analysis of the reaction profiles provided information on the catalyst deactivation pathway. The latter begins with the reduction of a Pd(II) Ar-BIAN complex to the corresponding Pd(0) species, a reaction that can be reverted by the action of benzoquinone. Then the ligand is lost, a process that appears to be facilitated by the contemporary coordination of an olefin or a CO molecule. The so formed Pd(0) complex immediately reacts with another molecule of the initial Pd(II) complex to give a Pd(I) dimeric species that irreversibly evolves to metallic palladium. Mechanistic investigations performed on the complex with a nonsymmetrical Ar-BIAN probe evidence that the detected intermediates are characterized by the Pd-C bond trans to the Pd-N bond of the aryl ring bearing electron-withdrawing substituents. In addition, the intermediate resulting from the insertion of 4-methylstyrene into the Pd-acyl bond is a five-member palladacycle and not the open-chain η(3)-allylic species observed for complexes with Ar-BIANs substituted in ortho position.
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http://dx.doi.org/10.1039/c3dt51425kDOI Listing
October 2013

Chiral cyclopropylamines in the synthesis of new ligands; first asymmetric Alkyl-BIAN compounds.

Chem Commun (Camb) 2010 Sep 23;46(33):6153-5. Epub 2010 Jul 23.

Università degli Studi di Milano, Dipartimento di Chimica Inorganica, Metallorganica e Analitica Lamberto Malatesta and ISTM-CNR, via Venezian 21, 20133 Milano, Italy.

The synthesis of new pinene-derived chiral cyclopropylamines and their use in the synthesis of the first asymmetric Alkyl-BIAN ligands (Alkyl-BIAN = bis-(alkylimino)acenaphthenequinone) are reported.
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http://dx.doi.org/10.1039/c0cc00977fDOI Listing
September 2010