Publications by authors named "Hoda A Ahmed"

9 Publications

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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

A new chiral boron-dipyrromethene (BODIPY)-based fluorescent probe: molecular docking, DFT, antibacterial and antioxidant approaches.

J Biomol Struct Dyn 2020 Nov 19;38(18):5429-5442. Epub 2019 Dec 19.

School of Chemistry, Bedson Building, Newcastle University, Newcastle upon Tyne, UK.

A new chiral BODIPY-based fluorescent compound, 5-bromo-4,4-difluoro-3(S)-1-phenylethyl)amino) BODIPY, was synthesized for biomedical applications. Optical, antimicrobial, antioxidant properties of the compound are investigated. The partition coefficient suggested that the compound has the potential to be developed as an active antibacterial and antioxidant candidate. In this context, antibacterial assay was carried out for compound against various bacterial strains, revealing maximum inhibition zone (24 ± 2.19 mm) in Moreover, results of antioxidant activity of compound revealed IC values to be greater than ascorbic acid. Molecular docking has given brief insight about the binding of the compound , suggesting that it has a strong potential to inhibit bacterial target enzymes DNA gyrase, enzymes in the type II fatty acid synthesis and Ddl (d-alanine: d-alanine ligase) in peptidoglycan synthesis. The molecular geometry and electrostatic potential of compound , was established by DFT (Density Functional Theory) calculations.AbbreviationsBBBblood‒brain barrierBDEbond dissociation energyBODIPYboron-dipyrromethaneDdlD-alanine:D-alanine ligaseDDQ2,3-dichloro-5,6-dicyano-1,4-benzoquinoneDFTdensity functional theoryDNAdeoxyribonucleic acidDPPH1,1‒diphenyl‒2‒picrylhydrazylNBS-bromo succinimideROSreactive oxygen speciesUV-visultraviolet-visibleFMOfrontier molecular orbitalsHOMOhighest occupied molecular orbitalLUMOlowest unoccupied molecular orbitalCommunicated by Ramaswamy H. Sarma.
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http://dx.doi.org/10.1080/07391102.2019.1701555DOI Listing
November 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