Experimental and Theoretical Approaches of New Nematogenic Chair Architectures of Supramolecular H-Bonded Liquid Crystals

New four isomeric chair architectures of 1:1 H-bonded supramolecular complexes were prepared through intermolecular interactions between 4-(2-(pyridin-4-yl)diazenyl-(2-(or 3-)chlorophenyl) 4-alkoxybenzoates and 4-n-alkoxybenzoic acids. The H-bond formation of all complexes was confirmed by differential scanning calorimetry (DSC) and Fourier-transform infrared spectroscopy (FTIR). Mesomorphic characterization was carried by DSC and polarized optical microscopy (POM). It was found that all prepared laterally chloro-substituted supramolecular complexes were nematogenic, and exhibited nematic phase and low melting temperature. The thermal stability of the nematic mesophase observed depends upon the location and spatial orientation of the lateral Cl− atom in as well as the length of terminal chains. Theoretical calculations were carried out within the paradigm of the density functional theory (DFT) in order to establish the molecular conformation for the formed complexes and estimate their thermal parameters. The results of the computational calculations revealed that the H-bonded complexes were in a chair form molecular geometry. Additionally, out of the acquired data, it was possible to designate the influence of the position and orientation of the lateral group as well as the alkoxy chain length on the stability of the nematic phase.

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Mesomorphic, Optical and DFT Aspects of Near to Room-Temperature Calamitic Liquid Crystal

Crystals ◽

10.3390/cryst10111044 ◽

2020 ◽

Vol 10 (11) ◽

pp. 1044

Author(s):

Ayman A. Zaki ◽

Mohamed Hagar ◽

Rua B. Alnoman ◽

Mariusz Jaremko ◽

Abdul-Hamid Emwas ◽

...

Keyword(s):

Density Functional ◽

Room Temperature ◽

Theoretical Calculations ◽

Fatty Acid Derivative ◽

Molecular Structures ◽

Resonance Spectroscopy ◽

Scanning Calorimetry ◽

Stable Conformer ◽

Geometrical Isomers ◽

Theoretical Approaches

A new liquid crystalline, optical material-based Schiff base core with a near to room-temperature mesophase, (4-methoxybenzylideneamino)phenyl oleate (I), was prepared from a natural fatty acid derivative, and its physical and chemical properties investigated by experimental and theoretical approaches. The molecular structure was confirmed by elemental analysis, FT-IR (Fourier-Transform-Infrared Spectroscopy) and NMR (nuclear magnetic resonance) spectroscopy. Optical and mesomorphic activities were characterized by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The results show that compound (I) exhibits an enantiotropic monomorphic phase comprising a smectic A phase within the near to room-temperature range. Ordinary and extraordinary refractive indices as well as birefringence with changeable temperatures were analyzed. Microscopic and macroscopic order parameters were also calculated. Theoretical density functional theory (DFT) calculations were carried out to estimate the geometrical molecular structures of the prepared compounds, and the DFT results were used to illustrate the mesomorphic results and optical characteristics in terms of their predicted data. Three geometrical isomers of the prepared compound were investigated to predict the most stable isomer. Many parameters were affected by the geometrical isomerism such as aspect ratio, planarity, and dipole moment. Thermal parameters of the theoretical calculations revealed that the highest co-planar aromatic core is the most stable conformer.

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

Molecules ◽

10.3390/molecules25071510 ◽

2020 ◽

Vol 25 (7) ◽

pp. 1510 ◽

Cited By ~ 3

Author(s):

Omaima A. Alhaddad ◽

Khulood A. Abu Al-Ola ◽

Mohamed Hagar ◽

Hoda A. Ahmed

Keyword(s):

Hydrogen Bonding ◽

Density Functional ◽

Liquid Crystalline ◽

Molecular Geometry ◽

Supramolecular Complexes ◽

Scanning Calorimetry ◽

Geometrical Structures ◽

Functional Theory ◽

Ft Ir ◽

Nematic Phases

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, n = 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 I/An are projected to exhibit a nonlinear geometry with V-shaped and chair-shaped geometry. The chair-shaped conformers of I/An 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 (TC) has been investigated by a comparative study of the present azo supramolecular H-bonding LCs (SMHBCs) I/An and our previously reported their Schiff base analogue complexes, II/An. 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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DFT STUDY OF THE PROTONATION AND DEPROTONATION ENTHALPIES OF BENZOXAZOLE, 1,2-BENZISOXAZOLE AND 2,1-BENZISOXAZOLE AND IMPLICATIONS FOR THE STRUCTURES AND ENERGIES OF THEIR ADDUCTS WITH EXPLICIT WATER MOLECULES

Journal of Theoretical and Computational Chemistry ◽

10.1142/s0219633613500703 ◽

2013 ◽

Vol 12 (07) ◽

pp. 1350070 ◽

Cited By ~ 11

Author(s):

MWADHAM M. KABANDA ◽

ENO E. EBENSO

Keyword(s):

Hydrogen Bonds ◽

Density Functional ◽

Biologically Active ◽

Basis Sets ◽

Water Molecules ◽

Intermolecular Hydrogen Bonds ◽

Theoretical Approaches ◽

Potential Applications ◽

The Stability ◽

Explicit Water

Benzoxazole, 1,2-benzisoxazole and 2,1-benzisoxazole are biologically active molecules with potential applications in drug design. Their interaction with aqueous medium in biological systems may be simulated by considering their interaction with explicit water molecules. Such studies provide information on the structures, energies and type of interactions stabilizing the resulting geometric systems. The objective of the current study was to utilize theoretical approaches to investigate the structures, stabilization energy and binding energy of benzoxazole–water, 1,2-benzisoxazole–water and 2,1-benzisoxazole–water complexes. The calculations were performed utilizing the density functional theory (DFT)/M06-2X/6-311 ++ G(d,p) method and the DFT/ωB97XD method with both the 6-311 ++ G(d,p) and the aug-cc-pVDZ basis sets. The results suggest that the stability of the different clusters depends on interrelated factors including the rings formed by intermolecular hydrogen bonds and the proton affinity (PA) or acidity of the atoms forming the intermolecular hydrogen bonds with the water molecules. A comparison across methods indicates that the results follow similar trends with different methods.

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Phase Behavior and DFT Calculations of Laterally Methyl Supramolecular Hydrogen-Bonding Complexes

Crystals ◽

10.3390/cryst9030133 ◽

2019 ◽

Vol 9 (3) ◽

pp. 133 ◽

Cited By ~ 21

Author(s):

Hoda Ahmed ◽

Mohamed Hagar ◽

Omaima Alhaddad

Keyword(s):

Differential Scanning Calorimetry ◽

High Stability ◽

Polarized Light ◽

Supramolecular Complexes ◽

Scanning Calorimetry ◽

Methyl Group ◽

Smectic C ◽

Computational Calculations ◽

Nematic Phases ◽

Hydrogen Bonded

Four new series of laterally methyl-substituted hydrogen-bonded supramolecular complexes were prepared. The prepared complexes were thermally investigated by differential scanning calorimetry (DSC) and phases identified by polarized light microscopy (PLM). Supramolecular hydrogen-bonded complexes formed from a 1:1 mixture of any two derivatives, bearing different alkoxy chains, of 4-alkoxyphenylazobenzoic acid and 4-(2-(pyridin-4-yl)diazenyl-(2-(or 3-)methylphenyl) 4-alkoxybenzoate. The investigated 1:1 mixture made by introducing a lateral methyl group by different spatial orientation angles into pyridine-based components. All new complexes were confirmed by Fourier-transform infrared spectroscopy (FTIR) and computational calculations used to study their stabilities. It is found that the prepared complexes are dimorphic, exhibiting smectic C and enhanced nematic phases. A comparison was made between the new series and previously investigated simpler complexes, revealed that the incorporation of the phenylazo group elongate the mesogenic part and hence broad nematic phases were obtained with high stability.

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Observation of Induced Luminescence and Thermochromism in Achiral Hydrogen Bonded Liquid Crystal Complexes

Zeitschrift für Physikalische Chemie ◽

10.1515/zpch-2020-1602 ◽

2020 ◽

Vol 234 (10) ◽

pp. 1709-1733

Author(s):

A. Ramya ◽

V. Balasubramanian ◽

R. Jayaprakasam ◽

V. N. Vijayakumar

Keyword(s):

Liquid Crystal ◽

Nematic Phase ◽

Density Functional ◽

Atomic Charge ◽

Optical Microscope ◽

Band Gap Energy ◽

Stability Factor ◽

Scanning Calorimetry ◽

Interesting Phenomenon ◽

Hydrogen Bonded

AbstractA novel hydrogen bonded liquid crystal (HBLC) complexes are obtained from the non-mesogenic (benzylmalonic acid) and mesogenic (p-n-alkyloxybenzoic acid, where n = 6, 7 and 8) compound via intermolecular hydrogen bonds (H-bond). H-bonds are experimentally confirmed by the Fourier transform infrared spectroscopic (FT-IR) studies and the same is validated using density functional theory (DFT). Induced thermochromism is observed by the polarizing optical microscope (POM) and its possible applications are reported. Phase transition temperature and their analogous enthalpy values, stability factor and span width are determined by the differential scanning calorimetry (DSC) studies. Band gap energy is calculated using UV-visible and photoluminescence spectrum. Hyper conjugative stabilization energy and atomic charge distribution is studied by the natural bond orbital (NBO) studies. Mulliken analysis clearly reveals the intermolecular interaction and steric effect of the HBLC complexes. An interesting phenomenon is that the observation of luminescence and thermochromism in the highly fluidity nematic phase. This peculiar behavior is attributed due to the intermolecular H-bonding interaction between the BMA and nOBA compounds and the effect of rotatory motion of the molecules in nematic phase. Luminescence increases when the spacer moiety decreases in the present complexes is also reported. In nematic phase, the molecules are in different degrees of the excited state which is correlated with the hyper conjugative energy through NBO studies.

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Synthesis, spectroscopic characterization and computational studies of Schiff base complexes of tin(IV) chloride

Main Group Metal Chemistry ◽

10.1515/mgmc-2019-0002 ◽

2019 ◽

Vol 42 (1) ◽

pp. 28-36

Author(s):

Nitesh Jaiswal ◽

Ajeet Kumar Kushwaha ◽

Avadhesh Pratap Singh ◽

Raj Kumar Dubey

Keyword(s):

Molecular Orbital ◽

Density Functional ◽

Molecular Geometry ◽

Spectroscopic Characterization ◽

Spectroscopic Studies ◽

Schiff Base Complexes ◽

Molar Ratios ◽

Highest Occupied Molecular Orbital ◽

Computational Calculations ◽

Lowest Unoccupied Molecular Orbital

Abstract Reaction of anhydrous tin(IV) chloride with mono functional bidentate Schiff bases (sbnH), in 1:2 molar ratios, gives complexes of the type, [(sbn)2SnCl2] (1-4) (where, n=1-4; sb=2-(((4-chlorophenyl)imino)methyl)phenol, sb1H, I; 2-(((4-bromophenyl)imino)methyl) phenol, sb2H, II; 2-(((4-chlorophenyl)imino)methyl)-6-methoxyphenol, sb3H, III and 2-(((4-bromo phenyl)imino)methyl)-6-methoxyphenol, sb4H, IV. All the tin(IV) complexes (1-4) were colored solid and soluble in organic solvents. The synthesized complexes were characterized by elemental analysis (C, H, N and Sn), IR, UV-Vis, NMR (1H, 13C and 119Sn) spectroscopy and mass spectrometry. On the basis of spectroscopic studies, six coordination around tin atom has been proposed tentatively. The computational calculations using density functional theory (DFT) of ligands and complexes were also performed to obtained optimized molecular geometry, the highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO) and other parameter.

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A THEORETICAL STUDY OF THE SUBSTITUENT EFFECT ON THE STABILITY OF COLLAGEN

Journal of Theoretical and Computational Chemistry ◽

10.1142/s0219633604001008 ◽

2004 ◽

Vol 03 (02) ◽

pp. 225-243 ◽

Cited By ~ 1

Author(s):

JUN-MIN QUAN ◽

YUN-DONG Wu

Keyword(s):

Electrostatic Interactions ◽

Triple Helix ◽

Density Functional ◽

Theoretical Calculations ◽

Substituent Effects ◽

Binding Energies ◽

Model Studies ◽

Collagen Triple Helix ◽

Triple Helices ◽

The Stability

Theoretical calculations have been carried out to investigate the effect of the 4(R)-substituents ( OH , F , NH 2, and [Formula: see text]) in proline on the stability of the collagen triple helix. A series of substituted proline models were studied first with density functional (B3LYP/6-31+G*) calculations. The solvent effect was studied using the SCIPCM method. While the F , OH and NH 2 groups increase the stability of the trans-up conformation with respect to the trans-down conformation, [Formula: see text] appears to favor the trans-down conformation in an aqueous solution. Second, the triple helices of the tripeptide models, Ac – Pro – Pro(X) – Gly – H with the two proline residues in the down/down and down/up puckering conformations, were optimized with a repeating unit approach using the HF/6-31G* method. For the Ac – Pro – Pro – Gly – H model peptide, the calculated binding energies of the two triple helices with the different puckering modes are similar. All four substituents, F , OH , NH 2, and [Formula: see text], considerably increased the binding energy of the down/up helix, but only [Formula: see text] stabilizes the down/down triple helix. Our calculations indicate that the inter-chain electrostatic interactions involving the 4(R)-substituents play an important role in stabilizing triple helical collagen models and allow the rationalization of all available experimental observations. Further model studies indicate that the substituent effects by the F , OH and NH 2 substituents are local while the effect of [Formula: see text] is long-range in nature.

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Binary Liquid Crystal Mixtures Based on Schiff Base Derivatives with Oriented Lateral Substituents

Crystals ◽

10.3390/cryst10040319 ◽

2020 ◽

Vol 10 (4) ◽

pp. 319 ◽

Cited By ~ 3

Author(s):

Rua B. Alnoman ◽

Mohamed Hagar ◽

Hoda A. Ahmed ◽

Magdi M. Naoum ◽

Hanefah A. Sobaih ◽

...

Keyword(s):

Schiff Base ◽

Binary Mixtures ◽

Density Functional ◽

Theoretical Calculations ◽

Geometrical Parameters ◽

Scanning Calorimetry ◽

Functional Theory ◽

Schiff Base Derivatives ◽

Lateral Group ◽

Molecular Stacking

Binary mixtures of the laterally substituted Schiff base/ester derivatives, namely 4-((2- or 3-) substituted phenyl imino methyl) phenyl-4”-alkoxy benzoates, Ia–d, were prepared and mesomorphically studied by differential scanning calorimetry (DSC) and their mesophases identified by polarized optical microscopy (POM). The lateral group (1-naphthyl, 2-F, 2-Br, 3-F in Ia–d, respectively) is attached to different positions of the phenyl Schiff moiety. The mixtures investigated were made from two differently shaped compounds that differ from each other in the polarity, size, orientation, and relative positions of the lateral group. The results revealed that the binary mixture Ia/Ib (bearing the naphthyl and 2-flouro substituents) exhibited the SmA phase, which covered the whole composition range. For the mixtures Ib/Id (2-F and 2-Br), the isomeric lateral F-group in compound Ib distributed the SmA arrangement of Id. In the Ic/Id mixture bearing two positionally and structurally different substituents, the addition of Ic to Id resulted in solid binary mixtures where its behavior may be attributed to the negligible steric effect of the small electronegative fluorine atom compared to the Br atom. Density functional theory (DFT) theoretical calculations were carried out to estimate the geometrical parameters of individual components and to show the effect of these parameters in the mesophase behavior of the binary system, where the higher dipole moment of Id (6 Debye) may be the reason for its high π–π molecular stacking, which influences its mesophase range and stability.

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

Molecules ◽

10.3390/molecules25071549 ◽

2020 ◽

Vol 25 (7) ◽

pp. 1549 ◽

Cited By ~ 6

Author(s):

Rua B. Alnoman ◽

Hoda A. Ahmed ◽

Mohamed Hagar ◽

Khulood A. Abu Al-Ola ◽

Bedor Sh. Alrefay ◽

...

Keyword(s):

Density Functional ◽

Aromatic Rings ◽

Scanning Calorimetry ◽

Thermal Stabilities ◽

Smectic C ◽

Computational Calculations ◽

Theoretical Predictions ◽

Temperature Ranges ◽

Homo And Lumo ◽

Ft Ir

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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Synthesis, Optical and DFT Characterizations of Laterally Fluorinated Phenyl Cinnamate Liquid Crystal Non-Symmetric System

Symmetry ◽

10.3390/sym13071145 ◽

2021 ◽

Vol 13 (7) ◽

pp. 1145

Author(s):

Laila A. Al-Mutabagani ◽

Latifah A. Alshabanah ◽

Hoda A. Ahmed ◽

Mohamed A. El-Atawy

Keyword(s):

Density Functional ◽

Liquid Crystalline ◽

Theoretical Calculations ◽

Symmetric System ◽

Scanning Calorimetry ◽

Geometrical Structures ◽

Functional Theory ◽

Computational Tools ◽

Meta Position ◽

Chain Lengths

A new laterally fluorinated unsymmetric liquid crystalline homologous series, based on cinnamate linkage, named 2-fluoro-4-(4-(alkoxy)phenyl)diazenyl)phenyl cinnamate (In), was synthesized and evaluated via different experimental and computational tools. The series had different terminal alkoxy-chain lengths with a lateral F atom in the meta position with respect to the azo moiety. The experimental mesomorphic and optical investigations were carried out using differential scanning calorimetry (DSC) and polarized optical microscopy (POM). Theoretical calculations and geometrical parameter predictions were conducted using the DFT program method at B3LYP/6-311G** level of theory. The results revealed that all the designed compounds exhibited the nematic (N) mesophase enantiotropically. The nematic stability and temperature range were impacted by the terminal alkoxy chain length. Compounds with the shortest chains (I6 and I8) showed a monotropic smectic A (SmA) phase, while the longest chain derivative, I16, possessed enantiotropic Sm A phase. Theoretical density functional theory (DFT) predictions were correlated with the practically observed data from the mesomorphic investigations. Data revealed that the terminal alkoxy and lateral F groups had an essential impact on the total energy of possible geometrical structures and their physical and thermal parameters.

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