Synthesis, Mesomorphic and Computational Characterizations of Nematogenic Schiff Base Derivatives in Pure and Mixed State.
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ABSTRACT:
SUBMITTER: Al-Mutabagani LA
PROVIDER: S-EPMC8038214 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:New asymmetrical Schiff base series based on lateral methoxy group in a central core, (E)-3-methoxy-4-(((4-methoxyphenyl)imino)methyl)phenyl 4-alkoxybenzoate (An), were synthesized and their optical and mesomorphic characteristics were investigated. The lateral OCH3group was inserted in the central ring in ortho position with respect to the azomethine linkage. FT-IR, and NMR spectroscopy as well as elemental analyses were used to elucidate their molecular structures. Their mesomorphic behaviors were characterized by polarized optical microscopy (POM) and differential scanning calorimetry (DSC). These examinations indicated that all the designed series were monomorphic and possessed nematic (N) mesophase enantiotropically, except A12 derivative which exhibited monotropic N phase. A comparative study was made between the present investigated series (An) and their corresponding isomers (Bn). The results revealed that the kind and stability of the mesophase as well as its temperature range are affected by the location and special orientation of the lateral methoxy group electric-resistance, conductance, energy-gap, and Urbach-energy were also reported for the present investigated An series. These results revealed that all electrodes exhibit Ohmic properties and electric-resistances in the GΩ range, whereas the electric resistance was decreased from 221.04 to 44.83 GΩ by lengthening the terminal alkoxy-chain to n = 12. The band gap of the An series was reduced from 3.43 to 2.89 eV by increasing the terminal chain length from n = 6 to n = 12 carbons. Therefore, controlling the length of the terminal chain can be used to improve the An series' electric conductivity and optical absorption, making it suitable for solar energy applications.
| S-EPMC8448195 | biostudies-literature
Project description:Two new homologues series, based on two rings of the azomethine central group bearing the terminal alkoxy group of various chain lengths, were prepared. The alkoxy chain length varied between 6 and 16 carbons. The other terminal wing in the first series was the F atom, and the compound is named N-4-florobenzylidene-4-(alkoxy)benzenamine (In). The second group of compounds included a lateral NO2 substituent in addition to the terminal F atom, named N-(4-fluoro-3-nitrobenzylidene)-4-(alkyloxy)aniline (IIn). Mesomorphic and optical properties were carried out via differential scanning calorimetry (DSC) and polarized optical microscopy (POM). Elemental analyses, FT-IR, and NMR spectroscopy were carried out to elucidate the molecular structures of the synthesized groups. Mesomorphic investigations indicated that all the synthesized homologues (In) were monomorphic, possessing the smectic A (SmA) phase monotropically, while the second group (IIn) members were non-mesomorphic. The experimental data indicated that the formation of the mesophase is affected by the protrusion of the lateral nitro group. The disruption of the mesophase in the second group was attributed to the increase of its molecular width, which affects its lateral intermolecular interactions. The computational simulations were in agreement with the experimental data. On the other hand, the location of NO2 group within the molecular geometry increased the melting temperature of the molecule, and thus, affected their thermal and physical properties. By discussing the estimated parameters, it was found that the molecular architecture, the dipole moment, and the polarizability of the investigated compounds are highly affected by the electronic nature and position of the terminal and lateral substituents as well as their volumes.
| S-EPMC8036588 | biostudies-literature
Project description:The thermal stability and mesomorphic behavior of a new biphenyl azomethine liquid crystal homologues series, (E)-4-(([1,1'-biphenyl]-4-ylmethylene)amino)phenyl 4-(alkoxy)benzoate, In, were investigated. The chemical structures of the synthesized compounds were characterized using FT-IR, NMR, and elemental analyses. Differential scanning calorimetry (DSC) and polarized optical microscopy were employed to evaluate the mesomorphic characteristics of the designed homologues. The examined homologues possessed high thermal stability and broad nematogenic temperature ranges. Furthermore, the homologues were covered by enantiotropic nematic phases. The experimental measurements of the mesomorphic behavior were substantiated by computational studies using the density functional theory (DFT) approach. The reactivity parameters, dipole moments, and polarizability of the studied molecules are discussed. The theoretical calculations demonstrated that as the chain length increased, the polarizability of the studied series increased; while it did not significantly affect the HOMO-LUMO energy gap and other reactivity descriptors, the biphenyl moiety had an essential impact on the stability of the possible geometries and their thermal as well as physical parameters.
| S-EPMC9268434 | biostudies-literature
Project description:Four new non-symmetrical derivatives based on central naphthalene moiety, 4-((4-(alkoxy)phenyl) diazenyl)naphthalen-1-yl 4-substitutedbenzoate (In/x), were prepared, and their properties were investigated experimentally and theoretically. The synthesized materials bear two wing groups: an alkoxy chain of differing proportionate length (n = 6 and 16 carbons) and one terminal attached to a polar group, X. Their molecular structures were elucidated via elemental analyses and FT-IR and NMR spectroscopy. Differential scanning calorimetry (DSC) and polarized optical microscopy (POM) were carried out to evaluate their mesomorphic properties. The results of the experimental investigations revealed that all the synthesized analogues possess only an enantiotropic nematic (N) mesophase with a high thermal stability and broad range. Density functional theory (DFT) calculations were in accordance with the experimental investigations and revealed that all prepared materials are to be linear and planar. Moreover, the rigidity of the molecule increased when an extra fused ring was inserted into the center of the structural shape, so its thermal and geometrical parameters were affected. Energy gap predictions confirmed that the I16/c derivative is more reactive than other compounds.
| S-EPMC8156059 | biostudies-literature
Project description: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, 1H-NMR, 13C-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(CH3)2, 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.
| S-EPMC6749398 | biostudies-literature
Project description:New mesomorphic series, 4-hexadecyloxy phenyl-imino-4'-(3-methoxyphenyl)-4″-alkoxybenzoates (An), were prepared and investigated with different thermal and mesomorphic techniques. The synthesized homologous series constitutes four members that differ from each other in the terminal length of flexible chain (n) attached to phenyl ester moiety, which varies between n = 6, 8, 10, and 12 carbons. A lateral CH3O group is attached to the central benzene ring in the meta position with respect to the ester moiety. Molecular structures of all newly prepared homologues were elucidated via FT-IR, 1H and 13C NMR spectroscopy. Mesomorphic and thermal properties were examined by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and the mesophases identified by polarized optical microscopy (POM). DSC and POM examinations revealed that all members of the present series (An) exhibit a purely enantiotropic nematic (N) phase. Comparative evaluations and binary phase diagrams were established between the present homologues and their corresponding shorter one (Bn). The examination revealed that, the length of the flexible alkoxy chain incorporated into the phenylimino moiety is highly effective on the temperature range and stability of the mesophase observed. With respect to the binary mixtures An/Bn, the exhibited N phase showed to cover the whole composition range with eutectic behavior.
| S-EPMC8196809 | biostudies-literature
Project description:A new set of laterally OCH3-substituted photoactive liquid crystalline analogues, 4-hexyloxy phenyl- imino-4'-(3-methoxyphenyl)-4''-alkoxybenzoates, were synthesized and investigated for their mesomorphic behavior. The prepared set constitutes five analogues that differ from each other by the terminally attached compact polar group. Characterization of the synthesized derivatives is conducted using differential scanning calorimetry (DSC), polarized optical microscopy (POM), and UV-spectroscopy. Molecular structures were elucidated by elemental analyses, FT-IR and NMR spectroscopy. DSC and POM investigations indicated that all the prepared derivatives are monomorphic possessing the nematic (N) phase, except for the unsubstituted derivative that is nonmesomorphic. On the other side, the photophysical study and the optical spectra measurements confirm the photoactivity of the present compounds under UV/visible irradiation. The measured optical spectra showed impressive enhancement in the optical absorption and reduction in the optical bandgap from 3.63 to 3.0 eV depending on the terminal group. From the study of the DC electric properties, the lowest resistance, 106.5 GΩ at scan rate 0.1 V/s, was observed for the I6d film with Cl terminal, which decreased to 49.5 GΩ by increasing the scan rate to 0.5 V/s. Moreover, the electrical conductance is decreased from 9.39 pS to 1.35 pS at scan rate 0.1 V/s by changing the terminal group from Cl to F. The enhanced optical absorption and the reduced energy gap make the optimized samples suitable material for solar energy applications.
| S-EPMC8269905 | biostudies-literature
Project description:BackgroundThiazole-based Schiff base compounds display significant pharmacological potential with an ability to modulate the activity of many enzymes involved in metabolism. They also demonstrated to have antibacterial, antifungal, anti-inflammatory, antioxidant, and antiproliferative activities. In this work, conventional and green approaches using ZnO nanoparticles as catalyst were used to synthesize thiazole-based Schiff base compounds.ResultsAmong the synthesized compounds, 11 showed good activities towards Gram-negative E. coli (14.40 ± 0.04), and Gram-positive S. aureus (15.00 ± 0.01 mm), respectively, at 200 μg/mL compared to amoxicillin (18.00 ± 0.01 mm and 17.00 ± 0.04). Compounds 7 and 9 displayed better DPPH radical scavenging potency with IC50 values of 3.6 and 3.65 μg/mL, respectively, compared to ascorbic acid (3.91 μg/mL). The binding affinity of the synthesized compounds against DNA gyrase B is within - 7.5 to - 6.0 kcal/mol, compared to amoxicillin (- 6.1 kcal/mol). The highest binding affinity was achieved for compounds 9 and 11 (- 6.9, and - 7.5 kcal/mol, respectively). Compounds 7 and 9 displayed the binding affinity values of - 5.3 to - 5.2 kcal/mol, respectively, against human peroxiredoxin 5. These values are higher than that of ascorbic acid (- 4.9 kcal/mol), in good agreement with the experimental findings. In silico cytotoxicity predictions showed that the synthesized compounds Lethal Dose (LD50) value are class three (50 ≤ LD50 ≤ 300), indicating that the compounds could be categorized under toxic class. Density functional theory calculations showed that the synthesized compounds have small band gap energies ranging from 1.795 to 2.242 eV, demonstrating that the compounds have good reactivities.ConclusionsThe synthesized compounds showed moderate to high antibacterial and antioxidant activities. The in vitro antibacterial activity and molecular docking analysis showed that compound 11 is a promising antibacterial therapeutics agent against E. coli, whereas compounds 7 and 9 were found to be promising antioxidant agents. Moreover, the green synthesis approach using ZnO nanoparticles as catalyst was found to be a very efficient method to synthesize biologically active compounds compared to the conventional method.
| S-EPMC8697436 | biostudies-literature
Project description:A series of Schiff bases (3.a-f) bearing benzimidazole moiety was successfully synthesized in ethanol by refluxing Oct-2-ynoic acid (1,3-dihydrobenzimidazole-2-ylidene)amide with substituted amines. Fourier transform infrared (FTIR), ultra violet light (UV-VIS), elemental analysis, proton (1H) and carbon (13C) nuclear magnetic resonance spectroscopy were used to characterize the newly synthesized Schiff bases. Micro dilution method was used to determine the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of the Schiff bases, against 14 human pathogenic bacteria (8 Gram negative and 6 Gram positive) and against 7 fungal strains (5 Aspergillus and 2 Fusarium) representatives. Antimalarial activity against Plasmodium falciparum and antitrypanosomal property against Trypanosoma brucei was studied in vitro at a single dose concentration of the Schiff bases. Cytotoxicity of the Schiff bases was assessed against human cervix adenocarcinoma (HeLa) cells. Results obtained show that the newly synthesized Schiff bases are very potent antimicrobial agents. Gram negative bacteria Klebsiella pneumonia and Escherichia coli were more affected on exposure to Compounds 3.c-f (MIC 7.8 µg/mL) which in turn exhibited more antibacterial potency than nalidixic acid reference drug that displayed MICs between 64 and 512 µg/mL against K. pneumonia and E. coli respectively. The test compounds also demonstrated high cytotoxic effect against Aspergillus flavus and Aspergillus carbonarius as they displayed MFC 7.8 and 15.6 µg/mL. Compound 3.c exhibited the highest fungicidal property from this series with MFC alternating between 7.8 and 15.6 µg/mL against the investigated strains. The malarial activity revealed Compounds 3.c and 3.d as the more potent antiplasmodial compounds in this group exhibiting 95% and 85% growth inhibition respectively. The IC50 of Compounds 3.c and 3.d were determined and found to be IC50 26.96 and 28.31 µg/mL respectively. Compound 3.a was the most cytotoxic agent against HeLa cells in this group with 48% cell growth inhibition. Compounds 3.c, 3.d and 3.f were biocompatible with HeLa cells and displayed low toxicity. With a very low cytotoxic effect against HeLa, compound 3.c stands out to be a very good antiparasitic agent and consideration to further evaluate the candidate drug against others cell lines is necessary.
| S-EPMC6842205 | biostudies-literature
Project description:Recently, chemical modifications of chitosan (CS) have attracted the attention of scientific researchers due to its wide range of applications. In this research, chitin (CH) was extracted from the scales of Cyprinus carpio fish and converted to CS by three chemical steps: (i) demineralization, (ii) deprotonation, and (iii) deacetylation. The degree (measured as a percentage) of deacetylation (DD %) was calculated utilizing the acid-base titration method. The structure of CS was characterized by Fourier transform infrared (FT-IR) spectroscopy and thermogravimetric analysis (TGA). Three new CS Schiff bases (CSSBs) (CS-P1, CS-P2, and CS-P3) were synthesized via coupling of CS with 2-chloroquinoline-3-carbaldehyde, quinazoline-6-carbaldehyde, and oxazole-4-carbaldehyde, respectively. The newly prepared derivatives were verified, structurally, by nuclear magnetic resonance (1H and 13C NMR) and FT-IR spectroscopy. Antimicrobial activity was evaluated for the prepared compounds against both "Gram-negative" and "Gram-positive" bacteria, namely, Escherichia coli, Klebsiella pneumonia, Staphylococcus aureus, and Streptococcus mutans, in addition to two kinds of fungi, Candida albicans and Aspergillus fumigates. Cytotoxicity of the synthesized CSSBs was evaluated via a MTT screening test. The results indicated a critical activity increase of the synthesized compound rather than CS generally tested bacteria and fungi and the absence of cytotoxic activity. These findings suggested that these new CSSBs are novel biomaterial candidates with enhanced antibacterial and nontoxic characteristics for applications in areas of both biology and medicine.
| S-EPMC7301590 | biostudies-literature