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Ahmed HA, Abolibda TZ, Ismail YAM, Almohammedi A, Aly KA, Ibrahim MS, Gomha SM. Novel maleic anhydride derivatives: liquid crystalline materials with enhanced mesomorphic and optical characteristics. Front Chem 2023; 11:1287883. [PMID: 38025055 PMCID: PMC10665853 DOI: 10.3389/fchem.2023.1287883] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2023] [Accepted: 10/30/2023] [Indexed: 12/01/2023] Open
Abstract
A new class of liquid crystalline materials, 4-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)phenyl 4-(alkoxy)benzoates (Mn), derived from maleic anhydride, was synthesized and studied for mesomorphic and optical properties. These materials consist of three derivatives with varying terminal flexible chain lengths (6-12 carbons) linked to the phenyl ring near the ester bond. The study employed differential scanning calorimetry and polarized optical microscopy (POM) to characterize the mesomorphic properties. Molecular structures were elucidated using elemental analysis, FT-IR, and NMR spectroscopy. The findings reveal that all the synthesized maleic anhydride derivatives exhibit enantiotropic nematic (N) mesophases. The insertion of the heterocyclic maleic anhydride moiety into the molecular structure influences the stability and range of the N phase. Additionally, entropy changes during N-isotropic transitions are of small magnitude and exhibit non-linear trends independent of the terminal alkoxy chain length (n). This suggests that the ester linkage group does not significantly promote molecular biaxiality, and the clearing temperature values are relatively high. By comparing the investigated materials with their furan derivatives found in existing literature, it was established that the substitution examined in this study induces the formation of nematic phases.
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Affiliation(s)
- Hoda A. Ahmed
- Department of Chemistry, Faculty of Science, Cairo University, Giza, Egypt
- Chemistry Department, College of Sciences, Taibah University, Yanbu, Saudi Arabia
| | - Tariq Z. Abolibda
- Department of Chemistry, Faculty of Science, Islamic University of Madinah, Madinah, Saudi Arabia
| | - Yasser A. M. Ismail
- Department of Physics, Faculty of Science, Islamic University of Madinah, Madinah, Saudi Arabia
| | - Abdullah Almohammedi
- Department of Physics, Faculty of Science, Islamic University of Madinah, Madinah, Saudi Arabia
| | - K. A. Aly
- Department of Physics, Collage of Science and Arts Khylais, University of Jeddah, Khulais, Saudi Arabia
- Department of Physics, Faculty of Science, Al-Azhar University, Assiut Branch, Assiut, Egypt
| | - Mohamed S. Ibrahim
- Department of Chemistry, Faculty of Science, Islamic University of Madinah, Madinah, Saudi Arabia
| | - Sobhi M. Gomha
- Department of Chemistry, Faculty of Science, Islamic University of Madinah, Madinah, Saudi Arabia
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Katariya KD, Nakum KJ, Soni H, Nada S, Hagar M. Imine Based Four-Ring Chalcone-Ester Liquid Crystals: Synthesis, Characterization, Mesomorphic Behaviour and DFT approach. J Mol Liq 2023. [DOI: 10.1016/j.molliq.2023.121719] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/30/2023]
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Mermer A, Boulebd H. An eco-friendly method for the synthesis of 1,2,4-triazole-Schiff base derivatives in aqueous medium and DFT calculations. J Mol Struct 2023. [DOI: 10.1016/j.molstruc.2022.134102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Ahmed HA, El-Atawy MA, Alamro FS, Al-Kadhi NS, Alhaddad OA, Omar AZ. Mesomorphic, Computational Investigations and Dyeing Applications of Laterally Substituted Dyes. MOLECULES (BASEL, SWITZERLAND) 2022; 27:molecules27248980. [PMID: 36558116 PMCID: PMC9785732 DOI: 10.3390/molecules27248980] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/28/2022] [Revised: 12/10/2022] [Accepted: 12/13/2022] [Indexed: 12/24/2022]
Abstract
Two groups of laterally substituted non-mesomorphic and liquid crystalline materials bearing monoazo group were prepared and investigated via experimental and theoretical techniques. The molecular structures of the designed dyes were evaluated by FT-IR and NMR spectroscopic analyses. Mesomorphic examinations for all synthesized dyes were investigated by polarized optical microscopy (POM) and differential scanning calorimetry (DSC). Results revealed that, the thermal and optical properties of investigated compounds are mainly dependent on their molecular geometry. The optimized geometries of the azo derivatives and their electronic absorption of the dyes were carried out using the B3LYP/6-311G level of the DFT method. The azo dyes were measured for their dyeing performance on polyester fabrics. The dyed fabrics have excellent fastness properties with a color strength of 1.49-3.43 and an exhaustion rate of 82-64%. The chemical descriptor parameters of disperse azo dyes in gas phase were calculated and correlated with dyeing parameters.
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Affiliation(s)
- Hoda A. Ahmed
- Department of Chemistry, Faculty of Science, Cairo University, Cairo 12613, Egypt
- Chemistry Department, Faculty of Science, Taibah University, Yanbu 46423, Saudi Arabia
- Correspondence:
| | - Mohamed A. El-Atawy
- Chemistry Department, Faculty of Science, Taibah University, Yanbu 46423, Saudi Arabia
- Chemistry Department, Faculty of Science, Alexandria University, P.O. Box 426 Ibrahemia, Alexandria 21321, Egypt
| | - Fowzia S. Alamro
- Department of Chemistry, College of Science, Princess Nourah bint Abdulrahman University, P.O. Box 84428, Riyadh 11671, Saudi Arabia
| | - Nada S. Al-Kadhi
- Department of Chemistry, College of Science, Princess Nourah bint Abdulrahman University, P.O. Box 84428, Riyadh 11671, Saudi Arabia
| | - Omaima A. Alhaddad
- Chemistry Department, College of Sciences, Taibah University, Al-Madina 30002, Saudi Arabia
| | - Alaa Z. Omar
- Chemistry Department, Faculty of Science, Alexandria University, P.O. Box 426 Ibrahemia, Alexandria 21321, Egypt
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Wu Q, Zhang H, Jia D, Liu T. Recent Development of Tunable Optical Devices Based on Liquid. Molecules 2022; 27:molecules27228025. [PMID: 36432123 PMCID: PMC9694320 DOI: 10.3390/molecules27228025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Revised: 11/13/2022] [Accepted: 11/14/2022] [Indexed: 11/22/2022] Open
Abstract
Liquid opens up a new stage of device tunability and gradually replaced solid-state devices and mechanical tuning. It optimizes the control method and improves the dynamic range of many optical devices, exhibiting several attractive features, such as rapid prototyping, miniaturization, easy integration and low power consumption. The advantage makes optical devices widely used in imaging, optical control, telecommunications, autopilot and lab-on-a-chip. Here, we review the tunable liquid devices, including isotropic liquid and anisotropic liquid crystal devices. Due to the unique characteristics of the two types of liquids, the tuning principles and tuning methods are distinguished and demonstrated in detail firstly and then some recent progress in this field, covering the adaptive lens, beam controller, beam filter, bending waveguide, iris, resonator and display devices. Finally, the limitations and future perspectives of the current liquid devices are discussed.
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Affiliation(s)
- Qi Wu
- School of Precision Instrument and Opto-Electronics Engineering, Tianjin University, Tianjin 300072, China
- Key Laboratory of Optoelectronic Information Technical Science, Tianjin University, Tianjin 300072, China
| | - Hongxia Zhang
- School of Precision Instrument and Opto-Electronics Engineering, Tianjin University, Tianjin 300072, China
- Key Laboratory of Optoelectronic Information Technical Science, Tianjin University, Tianjin 300072, China
- Correspondence:
| | - Dagong Jia
- School of Precision Instrument and Opto-Electronics Engineering, Tianjin University, Tianjin 300072, China
- Key Laboratory of Optoelectronic Information Technical Science, Tianjin University, Tianjin 300072, China
| | - Tiegen Liu
- School of Precision Instrument and Opto-Electronics Engineering, Tianjin University, Tianjin 300072, China
- Key Laboratory of Optoelectronic Information Technical Science, Tianjin University, Tianjin 300072, China
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Investigation of Corrosion Inhibition Potentials of Some Aminopyridine Schiff Bases Using Density Functional Theory and Monte Carlo Simulation. CHEMISTRY AFRICA 2022. [DOI: 10.1007/s42250-021-00304-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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Alamro FS, Al-Kadhi NS, Gomha SM, Popoola SA, Khushaim MS, Alhaddad OA, Ahmed HA. Experimental and Theoretical Investigations of Three-Ring Ester/Azomethine Materials. MATERIALS 2022; 15:ma15062312. [PMID: 35329764 PMCID: PMC8949326 DOI: 10.3390/ma15062312] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Revised: 03/10/2022] [Accepted: 03/18/2022] [Indexed: 12/26/2022]
Abstract
New three-ring ester/azomethine homologues series, (E)-4-((4-hydroxybenzylidene)amino)phenyl 4-(alkoxy)benzoate In, were prepared and their properties were investigated experimentally and theoretically. FT-IR, NMR, and elemental analyses were used to confirm the chemical structures of the synthesized compounds. The mesomorphic activities of the planned homologues were evaluated using differential scanning calorimetry (DSC) and polarized optical microscopy. All of the homologous examined were found to have non-mesomorphic properties. Theoretical calculations using the density functional theory (DFT) were used to validate the experimental data and determine the most stable conformation of the synthesized compounds. All calculated conformers’ thermal properties, dipole moments, and polarizability were discussed. The results show that the terminal alkoxy chain length affects the thermal parameters of the conformers. The correlations between these parameters’ values and the conformer type were demonstrated. The base component was expected to be in two conformers according to the orientation of the N atom of imine-linkage. DFT calculations revealed the more probable of the two possible conformers, and the incorporation of the alkoxy terminal chain in one position affect its geometrical and mesomerphic characteristics.
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Affiliation(s)
- Fowzia S. Alamro
- Department of Chemistry, College of Science, Princess Nourah bint Abdulrahman University, P.O. Box 84428, Riyadh 11671, Saudi Arabia; (F.S.A.); (N.S.A.-K.)
| | - Nada S. Al-Kadhi
- Department of Chemistry, College of Science, Princess Nourah bint Abdulrahman University, P.O. Box 84428, Riyadh 11671, Saudi Arabia; (F.S.A.); (N.S.A.-K.)
| | - Sobhi M. Gomha
- Chemistry Department, Faculty of Science, Islamic University of Madinah, Madinah 42351, Saudi Arabia;
- Department of Chemistry, Faculty of Science, Cairo University, Cairo 12613, Egypt
- Correspondence: (S.M.G.); (H.A.A.)
| | - Saheed A. Popoola
- Chemistry Department, Faculty of Science, Islamic University of Madinah, Madinah 42351, Saudi Arabia;
| | - Muna S. Khushaim
- Department of Physics, Faculty of Science, Taibah University, P.O. Box 30002, Al-Madina 41447, Saudi Arabia;
- Nanotechonolgy Center, Taibah University, P.O. Box 30002, Al-Madina 41447, Saudi Arabia
| | - Omaima A. Alhaddad
- Chemistry Department, College of Sciences, Taibah University, Madina Monawara 30002, Saudi Arabia;
| | - Hoda A. Ahmed
- Department of Chemistry, Faculty of Science, Cairo University, Cairo 12613, Egypt
- Chemistry Department, College of Sciences, Taibah University, Yanbu 30799, Saudi Arabia
- Correspondence: (S.M.G.); (H.A.A.)
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New Liquid Crystals Based on Terminal Fatty Chains and Polymorphic Phase Formation from Their Mixtures. CRYSTALS 2022. [DOI: 10.3390/cryst12030350] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The physical and chemical properties of three new liquid crystalline derivatives, based on an azomethine core with low-temperature mesophase—namely (4-methoxybenzylideneamino) phenyl palmitate (I), (4-methoxybenzylideneamino) phenyl oleate (II), and (4-methoxybenzylideneamino) phenyl linoleate (III)—were prepared and physically examined using experimental methodologies. Elemental analysis, FT-IR, and NMR spectroscopy were used to confirm their molecular structure. Differential scanning calorimetry (DSC) and polarized optical microscopy (POM) were used to investigate their mesomorphic activity. The results revealed that compound (I) is monotropic smectogenic, possessing the smectic A mesophase, whereas the other two analogues were shown to possess the SmA phase enantiotropically. Two of the saturated and unsaturated prepared derivatives (namely I and II) were used to construct their phase diagram. The eutectic composition of the mixture examined showed a slight enhancement of the stability of the smectic A phase. Polymorphic phases were produced at the eutectic composition of the binary phase diagram of the derivative II with the 4-n-dodecyloxy benzoic acid component.
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New Self-Organizing Optical Materials and Induced Polymorphic Phases of Their Mixtures Targeted for Energy Investigations. Polymers (Basel) 2022; 14:polym14030456. [PMID: 35160446 PMCID: PMC8838461 DOI: 10.3390/polym14030456] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2021] [Revised: 01/18/2022] [Accepted: 01/20/2022] [Indexed: 02/07/2023] Open
Abstract
Herein, a new homologues series of fluorinated liquid crystal compounds, In, 4-(((4-fluorophenyl)imino)methyl)-2-methoxyphenyl 4-alkoxybenzoate were synthesized and its mesomorphic properties were investigated both experimentally and theoretically. The synthesized compounds were characterized by elemental analyzer, NMR, and FT-IR spectroscopy to deduce the molecular structures. The differential scanning calorimetry was employed to examine mesophase transitions whereas the polarized optical microscopy was used to identify the mesophases. The obtained results revealed that the purely nematic phase observed in all terminal side chains. All homologues showed to possess monotropic nematic mesophases except the derivative I8 exhibits enantiotropic property. The optimized geometrical structures of the present designed groups have been derived theoretically. The experimental data was explained using density functional theory computations. The estimated values of dipole moment, polarizability, thermal energy, and molecule electrostatic potential demonstrated that the mesophase stability and type could be illustrated. Binary phase diagram was constructed and addressed in terms of the mesomorphic temperature range and obtained polymorphic phases. It was found that incorporation of the terminal F-atom and lateral CH3O group influence both conformation and steric effect in pure and mixed states. The absorption and fluorescence emission spectra of fabricated films were recorded to elucidate the impact of terminal side chain on photophysical properties of synthesized liquid crystal. It was noted that the increase of terminal side chain length lead to reduction of optical band gap, whereas charge carrier lifetime increases.
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Alamro FS, Alhaddad OA, Naoum MM, Ahmed HA. Polymorphic Phases of Supramolecular Liquid Crystal Complexes Laterally Substituted with Chlorine. Polymers (Basel) 2021; 13:4292. [PMID: 34960843 PMCID: PMC8703890 DOI: 10.3390/polym13244292] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Revised: 12/03/2021] [Accepted: 12/06/2021] [Indexed: 11/17/2022] Open
Abstract
New supramolecular complexes, based on H-bonding interactions between 4-(pyridin-4-yl) azo-(2-chlorophenyl) 4-alkoxybenzoates (Bn) and 4-[(4-(n-hexyloxy)phenylimino)methyl]benzoic acid (A6), were prepared and their thermal and mesomorphic properties investigated via differential scanning calorimetry (DSC) and Fourier-transform infrared spectroscopy (FT-IR) in order to confirm their H-bonding interactions. The mesophase behavior of each mixture was examined by DSC and polarized optical microscopy (POM). According to the findings of the study, in all of the designed mixtures, the introduction of laterally polar chlorine atom to the supramolecular complexes produces polymorphic compounds possessing smectic A, smectic C and nematic mesophases, in addition, all products have low melting transitions. Thermal stabilities of the associated phases depend on the position and orientation of the lateral polar Cl- atom as well as the length of terminal flexible alkoxy chain. Comparisons were made between the present lateral Cl- complexes and previously investigated laterally-neat complexes in order to investigate the impact of the addition, nature and orientation of polar substituent on the mesomorphic behavior. The investigations revealed that, the polarity and mesomeric nature of inserted lateral substituent into the base component play an essential role in affecting their mesomorphic properties. Furthermore, for current complexes, induced polymorphic phases have been found by introducing the chlorine atom.
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Affiliation(s)
- Fowzia S. Alamro
- Department of Chemistry, College of Science, Princess Nourah Bint Abdulrahman University, Riyadh 11671, Saudi Arabia;
| | - Omaima A. Alhaddad
- Chemistry Department, College of Sciences, Taibah University, Madina Monawara 30002, Saudi Arabia;
| | - Magdi M. Naoum
- Department of Chemistry, Faculty of Science, Cairo University, Cairo 12613, Egypt;
| | - Hoda A. Ahmed
- Department of Chemistry, Faculty of Science, Cairo University, Cairo 12613, Egypt;
- Chemistry Department, College of Sciences, Taibah University, Yanbu 30799, Saudi Arabia
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Alamro FS, Ahmed HA, Popoola SA, Aboelnaga A. Synthesis, Phase Behavior and Computational Simulations of a Pyridyl-Based Liquid Crystal System. Molecules 2021; 26:6416. [PMID: 34770826 PMCID: PMC8588046 DOI: 10.3390/molecules26216416] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2021] [Revised: 10/13/2021] [Accepted: 10/21/2021] [Indexed: 01/30/2023] Open
Abstract
A homologous set of liquid crystalline materials (Tn) bearing Schiff base/ester linkages were prepared and investigated via experimental and theoretical techniques. Terminal flexible groups of different chain lengths were connected to the end of phenylbenzoate unit while the other end of molecules was attached to the heterocyclic pyridine moiety. The molecular structures of the designed molecules were evaluated by FT-IR, NMR spectroscopic analyses, whereas their mesomorphic properties were investigated by polarized optical microscopy (POM) and differential scanning calorimetry (DSC). They all exhibited dimorphic properties with the exception of the members having the shortest and longest terminal flexible chains (n = 6 and 16), which were monomorphic. The T16 derivative was further found possessing purely smectic A (SmA) mesophase while others have their lengths covered by nematic (N) phase. Moreover, the computational evaluation of the azomethine derivatives was carried out using a DFT approach. The polarity of the investigated derivatives was predicted to be appreciably sensitive to the size of the system. Furthermore, the Frontier molecular orbitals analysis revealed various distributions of electron clouds at HOMO and LUMO levels.
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Affiliation(s)
- Fowzia S. Alamro
- Department of Chemistry, College of Science, Princess Nourah Bint Abdulrahman University, Riyadh 11671, Saudi Arabia;
| | - Hoda A. Ahmed
- Department of Chemistry, Faculty of Science, Cairo University, Cairo 12613, Egypt
- Chemistry Department, College of Sciences, Taibah University, Yanbu 30799, Saudi Arabia
| | - Saheed A. Popoola
- Chemistry Department, Faculty of Science, Islamic University of Madinah, Al-Madinah Al-Munawwarah 42351, Saudi Arabia;
| | - Asmaa Aboelnaga
- Department of Chemistry, Faculty of Women for Arts, Science and Education, Ain Shams University, Cairo 11566, Egypt;
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Alamro FS, Ahmed HA, El-Atawy MA, Al-Zahrani SA, Omar AZ. Induced Nematic Phase of New Synthesized Laterally Fluorinated Azo/Ester Derivatives. Molecules 2021; 26:4546. [PMID: 34361699 PMCID: PMC8347854 DOI: 10.3390/molecules26154546] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2021] [Revised: 07/23/2021] [Accepted: 07/26/2021] [Indexed: 01/04/2023] Open
Abstract
A new series of laterally fluorinated mesomorphic compounds, namely 2-fluoro-4-((4-(alkyloxy)phenyl)diazenyl)phenyl 4-substitutedbenzoate (Inx) were prepared and evaluated for their mesophase behavior. The synthesized series constitutes five members that possess different terminally attached polar groups (X). Their molecular structures were confirmed by elemental analyses and both FT-IR and NMR spectroscopy. Examination of the prepared derivatives was conducted via experimental and theoretical tools. Mesomorphic investigations were carried by polarized optical microscopy (POM) and differential scanning calorimetry (DSC). DSC and POM measurements indicated that except for the un-substituted analogue, all other derivatives were purely nematogenic, possessing their nematic (N) mesophase enantiotropically. This is to say that insertions of terminal polar substituents on their mesogenic structures induced the N phase. In addition, the location of lateral and terminal polar moieties played a considerable role in achieving good thermal N stability. Computational calculations were investigated to determine the deduced optimized molecular structures. Theoretical data indicated that both size and polarity of the terminal substituent (X) have essential impact on the thermal parameters and optical properties of possible geometries.
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Affiliation(s)
- Fowzia S. Alamro
- Department of Chemistry, College of Science, Princess Nourah bint Abdulrahman University, Riyadh 11671, Saudi Arabia;
| | - Hoda A. Ahmed
- Department of Chemistry, Faculty of Science, Cairo University, Cairo 12613, Egypt
- Chemistry Department, Faculty of Science, Taibah University, Yanbu 46423, Saudi Arabia
| | - Mohamed A. El-Atawy
- Chemistry Department, Faculty of Science, Taibah University, Yanbu 46423, Saudi Arabia
- Chemistry Department, Faculty of Science, Alexandria University, P.O. Box 426 Ibrahemia, Alexandria 21321, Egypt;
| | - Salma A. Al-Zahrani
- Department of Chemistry, College of Sciences, University of Ha’il, Ha’il 2440, Saudi Arabia;
| | - Alaa Z. Omar
- Chemistry Department, Faculty of Science, Alexandria University, P.O. Box 426 Ibrahemia, Alexandria 21321, Egypt;
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Effect of the Relative Positions of Di-Laterally Substituted Schiff Base Derivatives: Phase Transition and Computational Investigations. CRYSTALS 2021. [DOI: 10.3390/cryst11080870] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Two new laterally di-substituted derivatives namely, (E)-4-(((2-Chlorophenyl)imino)methyl)-3-methoxyphenyl 4-(alkoxy)benzoate, were designed and investigated for their mesomorphic properties. Elucidation of their molecular structures was carried out by elemental analyses, NMR and FT-IR, spectroscopy. Phase transitions were examined by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The optimized geometrical architectures of both compounds were deduced theoretically using GAUSSIAN 09 program. In order to establish the most probable conformation for each compound, four probable conformations were predicted for their positional isomers which vary according to the orientations of the two lateral groups. The results were used to correlate the experimental measurements with the predicted conformations. The study revealed that the investigated derivatives are non-mesomorphic and the orientations, as well as positions of the two-lateral groups, have a significant effect on the molecular packing of the molecules, their geometrical and thermal parameters.
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