15872-43-2Relevant academic research and scientific papers
Synthesis of novel liquid crystalline and fire retardant molecules based on six-armed cyclotriphosphazene core containing Schiff base and amide linking units
Guan-Seng, Tay,Jamain, Zuhair,Khairuddean, Melati
, p. 28918 - 28934 (2020/08/25)
Nucleophilic substitution reaction between 4-hydroxybenzaldehyde and hexachlorocyclotriphosphazene, HCCP formed hexakis(4-formlyphenoxy)cyclotriphosphazene, 1. Intermediates 2a-e was formed from the alkylation reaction of methyl 4-hydroxybenzoate with alkyl bromide which further reduced to form benzoic acid intermediates. Further reaction of 2a-e and other substituted benzoic acid formed 3a-h, which then reduced to give subsequent amines, 4a-h. Other similar reaction was used to synthesis 4i. Condensation reaction between 1 and 4a-i yielded hexasubstituted cyclotriphosphazene compounds, 5a-i having Schiff base and amide linking units, and these compounds consist of different terminal substituents such as heptyl, nonyl, decyl, dodecyl, tetradecyl, hydroxy, carboxy, chloro, and nitro groups, respectively. Compound 5j with amino substituent at terminal end was formed from the reduction of 5i. All the intermediates and compounds were characterized using Fourier Transform Infrared (FT-IR), Nuclear Magnetic Resonance (NMR) and CHN elemental analysis. Mesophase texture of these compounds were determined using Polarized Optical Microscope (POM) and their mesophase transition were further confirmed using Differential Scanning Calorimetry (DSC). Only compounds 5a-e with alkoxy chains exhibited smectic A phase while other intermediates (1, 2a-e, 3a-h, and 4a-i) and final compounds (5f-j) are found to be non-mesogenic with no liquid crystal behaviour. The confirmation of the identity of the SmA phase was determined using XRD analysis. The study on the structure-properties relationship was conducted in order to determine the effect of the terminal group, length of the chains and linking units to the mesophase behaviour of the compounds. Moreover, the fire retardant properties of these compounds were determined using Limiting Oxygen Index (LOI) testing. Polyester resin with LOI value of 22.53% was used as matrix for moulding in the study. The LOI value increased to 24.71% when this polyester resin incorporated with 1 wt% of HCCP. Generally, all the final compounds showed a positive results with LOI value above 27% and the highest LOI value was belonged to compound 5i with 28.53%. The high thermal stability of the Schiff base molecules and the electron withdrawing group of the amide bonds and nitro group enhanced the fire retardant properties of this compound.
Hydrogen bonding and the design of twist-bend nematogens
Crawford, Catriona A.,Gorecka, Ewa,Imrie, Corrie T.,Pociecha, Damian,Storey, John M. D.,Walker, Rebecca
, (2020/02/13)
The phase properties of equimolar mixtures consisting of a hydrogen bond donor, a 4-alkoxybenzoic acid (nOBA), and one of two different stilbazole-based hydrogen bond acceptors, either 4-[(E)-2-(4-{[6-(4′-methoxy[1,1′-biphenyl]-4-yl)hexyl]oxy}phenyl)-ethenyl]-pyridine (1OB6OS) or 4-[(E)-4′-(6-{4-[(E)-2-(pyridin-4-yl)ethenyl]phenoxy}hexyl)-[1,1′-biphenyl]-4-carbonitrile (CB6OS) are reported. Neither hydrogen bond acceptor exhibits liquid crystal behaviour whereas the nOBA compounds show smectic and/or nematic behaviour depending on the length of the alkyloxy chain. For the complexes of an nOBA with n = 1–5, both conventional nematic and twist-bend nematic phases were observed, while for n ≥ 6 smectic phases emerged and the twist-bend nematic phase was extinguished. The CB6OS-nOBA mixtures may exhibit the heliconical smectic CTB phase. The local molecular arrangement in the two sets of mixtures are similar and changes on increasing n but this is not reflected in the nematic-isotropic transition temperatures. Birefringence studies of the mixtures are reported. In general the behaviour of the hydrogen-bonded mixtures is similar to that of their covalently bonded counterparts.
Coumarin substituted symmetric diaminopyridine molecules: Synthesis, mesomorphic characterizations and DFT studies
Al-Mohammed, Mohammad Hameed,Ameen, Wissam Ahmed,Mohammad, AbdulKarim-Talaq,Srinivasa, H. T.
, (2020/07/30)
The 2, 6-diaminopyridine was symmetrically substituted with coumarins from a lateral side of the molecules. All the molecules characterized by standard spectroscopic methods such as infrared spectroscopy, and nuclear magnetic resonance spectroscopy techniques. Mesomorphic properties are evaluated by the differential scanning calorimetry and the polarized optical microscope. The measurements show that the lower members did not favour liquid crystal formation, while higher members are exhibiting liquid crystalline, namely Nematic mesophase. The DFT computations manifest the nature of liquid crystal geometrical aspects.
2-Aryl benzazole derived new class of anti-tubercular compounds: Endowed to eradicate mycobacterium tuberculosis in replicating and non-replicating forms
Datta, Dhrubajyoti,Debnath, Joy,Franzblau, Scott G.,Ghosh, Kalyan Sundar,Hari, Natarajan,Ma, Rui,Rana, Shiwani,Velappan, Anand Babu
, (2020/09/04)
The high mortality rate and the increasing prevalence of Mtb resistance are the major concerns for the Tuberculosis (TB) treatment in this century. To counteract the prevalence of Mtb resistance, we have synthesized 2-aryl benzazole based dual targeted molecules. Compound 9m and 9n were found to be equally active against replicating and non-replicating form of Mtb (MIC(MABA) 1.98 and 1.66 μg/ml; MIC(LORA) 2.06 and 1.59 μg/ml respectively). They arrested the cell division (replicating Mtb) by inhibiting the GTPase activity of FtsZ with IC50 values 45 and 64 μM respectively. They were also capable of kill Mtb in non-replicating form by inhibiting the biosynthesis of menaquinone which was substantiated by the MenG inhibition (IC50 = 11.62 and 7.49 μM respectively) followed by the Vit-K2 rescue study and ATP production assay.
Synthesis, characterization, crystal structure and liquid crystal studies of some symmetric naphthalene derivative molecules
Srinivasa,Palakshamurthy,Devarajegowda,Hariprasad
, p. 620 - 626 (2018/09/18)
The synthesis of a series of symmetrical liquid crystals having naphthalene as the central rigid core and attached to long chain flexible 4′-alkoxybenzoate moiety at positions 2,6 - of the aromatic ring are reported. The mesophase behavior of the molecules was investigated using differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and X-ray diffraction studies. The studies reveal that the synthesized compounds exhibit stable enantiotropic mesophase of Smectic A (SmA) and Nematic (N) phase. The mesophase appearance is independent of the length of the alkyl chain. The molecular structure was determined by single crystal X-ray diffraction technique. The derivative with n-heptyloxy- flexible chain crystallizes under triclinic, P1ˉspace group with unit cell dimension a = 5.569(3) ? b = 10.540(5) ? c = 15.254(9) ? α = 73.434(18)o, β = 80.807(19)o and γ = 82.02(2)o, V = 843.1(8) ?3. The dihedral angle between the naphthalene ring system and the benzoate moiety is 63.63(2)o.
Ferroelectric Liquid Crystals: Synthesis and Thermal Behavior of Optically Active, Three-Ring Schiff Bases and Salicylaldimines
Veerabhadraswamy, Bhyranalyar N.,Rao, Doddamane S. Shankar,Yelamaggad, Channabasaveshwar V.
, p. 1012 - 1023 (2018/04/23)
The chiral ferroelectric smectic C (SmC*) phase, characterized by a helical superstructure, has been well exploited in developing high-resolution microdisplays that have been effectively employed in the fabrication of a wide varieties of portable devices. Although, an overwhelming number of optically active (chiral) liquid crystals (LCs) exhibiting a SmC* phase have been designed and synthesized, the search for new systems continues so as to realize mesogens capable of meeting technical necessities and specifications for their end-use. In continuation of our research work in this direction, herein we report the design, synthesis, and thermal behavior of twenty new optically active, three-ring calamitic LCs belonging to four series. The first two series comprise five pairs of enantiomeric Schiff bases whereas the other two series are composed of five pairs of enantiomeric salicylaldimines. In each pair of optical isomers, the configuration of a chiral center in one stereoisomer is opposite to that of the analogous center in the other isomer as they are derived from (3 S)-3,7-dimethyloctyloxy and (3 R)-3,7-dimethyloctyloxy tails. To probe the structure–property correlations in each series, the length of the n-alkoxy tail situated at the other end of the mesogens has been varied from n-octyloxy to n-dodecyloxy. The measurement of optical activity of these chiral mesogens was carried out by recording their specific rotations. As expected, enantiomers rotate plane polarized light in the opposite direction but by the same magnitude. The thermal behavior of the compounds was established by using a combination of optical polarizing microscopy, differential scanning calorimetry, and powder X-ray diffraction. These complementary techniques demonstrate the existence of the expected, thermodynamically stable, chiral smectic C (SmC*) LC phase besides blue phase I/II (BPI or BPII) and chiral nematic (N*) phase. However, as noted in our previous analogous study, the vast majority of the Schiff bases show an additional metastable, unfamiliar smectic (SmX) phase just below the SmC* phase. Notably, the SmC* phase persists over the temperature range ≈80–115 °C. Two mesogens chosen each from Schiff bases and salicylaldimines were investigated for their electrical switching behavior. The study reveals the ferroelectric switching characteristics of the SmC* phase featuring the spontaneous polarization (PS) in the range 69–96 nC cm?2. The helical twist sense of the SmC* phase as well as the N* phase formed by a pair of enantiomeric Schiff bases and salicylaldimines has been established with the help of circular dichroism (CD) spectroscopic technique. As expected, the SmC* and the N* phase of a pair of enantiomers showed mirror image CD signals. Most importantly, the reversal of helical handedness from left to right and vice versa has been evidenced during the N* to SmC* phase transition, implying that the screw sense of the helical array of the N* phase and the SmC* phase of an enantiomer is opposite.
Hydrogen-bonded bent-core blue phase liquid crystal complexes containing various molar ratios of proton acceptors and donors
Han, Chun-Chieh,Chou, Yu-Chaing,Chen, San-Yuan,Lin, Hong-Cheu
, p. 32319 - 32327 (2016/04/26)
Various hydrogen-bonded (H-bonded) bent-core liquid crystal complexes consisting of pyridyl and benzoic acid derivatives were synthesized and compared with their covalent analogues in this study. The molar ratios of pyridyl and benzoic acid derivatives could be tuned to form various H-bonded liquid crystal (LC) diads (with 1:1 molar ratio of H-acceptors T and H-donors D) and complexes (with different molar ratios of T and D). By insertion of H-bonds into different positions of bent-core supramolecules, the mesophasic properties of H-bonded bent-core LC complexes were optimized, which could facilitate the most suitable LC components and compositions to be utilized in H-bonded blue phase (BP) LC complexes. In BPLC complexes, the molar ratios, alkyl chain lengths, the lateral fluoro-substitution and the chiral center of H-bonded bent-core supramolecules would affect the temperature ranges of BPs. Accordingly, H-bonded bent-core complex PIIIC9/AIIF? (3/7 mol mol-1) displayed the widest BPI range of ΔTBPI = 12.0 °C at the correspondent H-acceptor T = PIIIC9 and H-donor D = AIIF?. Since the covalent-bonded bent-core mixture only had narrow ranges of BPIII, we could summarize that the introduction of H-bonds into the bent-core center effectively stabilizes the BPs and easier induces the BPI.
Triphenylene derivative and use thereof
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Page/Page column 9; 10, (2016/05/19)
A triphenylene derivative of general formula (I) or general formula (II) which can be used as a component of liquid crystal medium and the use thereof are provided in the present invention. This compound can be used to form a negative discotic liquid crystal composition having a suitable temperature range of liquid crystal phase and a lower clearing point, which can be used in TFT liquid crystal display as an optical compensation film (cell) material.
Optically active, three-ring calamitic liquid crystals: The occurrence of frustrated, helical and polar fluid mesophases
Veerabhadraswamy,Rao, D. S. Shankar,Prasad, S. Krishna,Yelamaggad
, p. 2011 - 2027 (2015/03/30)
Herein, we report on the synthesis, characterization, liquid crystalline behavior and chirooptical properties of five (R)-4-{[(4-(octan-2-yloxy)phenyl)imino]methyl}phenyl 4-(n-alkoxy)benzoates and their enantiomers, namely, (S)-4-{[(4-(octan-2-yloxy)phenyl)imino]methyl}phenyl 4-(n-alkoxy)benzoates. These three-ring rod-like mesogens were prepared by acid catalyzed condensation of (R)-/(S)-4-(octan-2-yloxy)anilines with 4-formylphenyl 4-(n-alkoxy)benzoates. Thus, each pair of enantiomers comprises (R)-2-octyloxy and (S)-2-octyloxy chiral tails. In order to understand the structure-property correlations, the length of the paraffinic chain incorporated at the other end has been varied from n-octyloxy to n-dodecyloxy. A detailed study carried out by means of several complimentary techniques reveals the stabilization of liquid crystal phases that hold great promise in applied sciences especially in various device applications. In particular, the occurrence of mesophases such as the blue phase-I/II (BPI or BPII) and chiral nematic (N) and chiral smectic C (SmC) phases has been evidenced unequivocally with the help of polarizing microscopy, differential scanning calorimetry, X-ray diffraction and electrical switching. Besides, the occurrence of an unknown, metastable smectic (SmX) phase below the SmC phase has been noted. This study shows that the length of the terminal tail seems to determine the thermal range of the SmC phase. The enantiotropic SmC phase exhibiting ferroelectric switching behavior occurs over 60 °C thermal range; notably, the spontaneous polarization (Ps) value crosses over 100 nC cm-2. The photophysical properties and chirooptical behavior of the mesogens have been studied with the aid of UV-vis absorption and circular dichroism (CD) spectroscopic methods, respectively; the latter technique has been especially used to ascertain the twist sense of the N and SmC phases formed by a pair of enantiomers. The reversal of the helix-sense (from right to left and vice versa) during the N-SmC phase transition has been observed for the first time.
Stable ferroelectric liquid crystals derived from salicylaldimine-core
Veerabhadraswamy, Bhyranalyar N.,Rao, D. S. Shankar,Yelamaggad, Channabasaveshwar V.
, p. 4539 - 4551 (2015/04/14)
Five pairs of enantiomers derived from salicylaldimine-core have been prepared by condensing (R)- or (S)-4-(octan-2-yloxy)anilines with 4-formyl-3-hydroxyphenyl 4-(n-alkoxy)benzoates. They have been designed to probe the correlation between molecular structure and mesomorphism, and especially to provide stable mesogens having potential for applications in ferroelectric liquid crystal devices. Thus, they have been substituted with a chiral tail at one end and by n-alkoxy chains of varying length at the other terminal. A detailed study confirms an indistinguishable behavior of all ten mesogens exhibiting an enantiotropic chiral smectic C (SmC) phase besides blue phase (BP) and chiral nematic (N) phase. The SmC phase occurring over a 50-70 °C thermal width shows ferroelectric switching with spontaneous polarization (Ps) value crossing over 100 nC/cm2. Circular dichroism spectroscopic study of the mesophases confirms the chromophores of the molecules being in the macroscopic chiral (helical) environment.
