- Synthesis and Study of Novel Mesogenic Homologous Series: 4-(4′- n -alkoxy benzoyloxy)- n -propyl Cinnamates
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A novel homologous series of liquid crystals viz. 4-(4′-n-alkoxy benzoyloxy) n-propyl cinnamates comprising of 11 homologues has been synthesized. It is a middle ordered melting type of series with exhibition of smectic and nematic mesophases. The first to fifth members of the series are non-mesomorphic. Mesomorphic behavior commences from the sixth homologue. The octyloxy (C8) and decyloxy (C10) homologues are polymesomorphic. The smectic-nematic and nematic-isotropic transition curves behave in a normal manner except for the hexadecyl derivative, which slightly deviates from normal behavior (N-I). An odd-even effect was not observed for the N-I or Sm-N transition curves. The texture of nematic phase is threaded or Schlieren and that of the smectic phase is focal conic fan shaped of the smectic-A type. Transition temperatures and textures of mesophases were observed through an optical polarizing microscope equipped with a heating stage. Thermal stability and mesomorphic characteristics are compared with a structurally related series. Analytical and spectral data support the structure of the molecules.
- Chauhan,Doshi,Sheth
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- Synthesis and study of liquid crystal properties of novel homologous series: α-4-[-4′-n-alkoxy benzoyloxy] phenyl β-4″-nitro benzoyl ethylenes
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The synthesis and mesomorphic properties of a novel homologous series entitled α-4-[-4′-n-Alkoxy benzoyloxy] phenyl β-4 ″-nitro benzoyl ethylenes are reported. All the 11 members of the series except the methoxy and ethoxy derivatives are mesogenic. The propyloxy to pentyloxy and the hexadecyloxy homologues are only enantiotropically nematogenic and the rest of the mesogenic homologues are enantiotropically smectogenic in addition to nematogenic in character. A phase diagram shows the phase behavior through transition curves is of a normal type. An odd-even effect is observed for the nematic-isotropic transition curve. Analytical and spectral data support the molecular structure of the materials. Transition temperatures and other liquid crystal (LC) properties including average thermal stabilities for smectic and nematic were determined by optical polarizing microscopy. Average thermal stability for smectic and nematic are 125.6°C and 154.6°C, respectively. Smectogenic and nematogenic phase ranges vary between 19°C to 35°C and 14°C to 50°C, respectively. The LC properties of the novel series are compared with two other structurally similar homologous series. The textures of the nematic phase are threaded or schlieren type and those of the smectic phase is of the type A or C.
- Suthar,Doshi
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- Mesomorphism and Molecular Structure of Ester Homologous Series Containing Carboxy and Vinyl Carboxy Linking Groups
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A novel homologous series 4-(4′-n-alkoxy benzoyloxy)-isopentyl cinnamates consisting of eleven homologs is reported. Mesomorphism commences from the hexyloxy homolog up to the hexadecyloxy homolog. The hexyloxy and hexadecyloxy derivatives are only enantiotropically nematogenic while, but the octyl, decyl, dodecyl, and tetradecyl homologs exhibit enantiotropic nematogenic and smectogenic mesophases. The rest of the homologs are nonmesogenic. The textures of nematic phase are threaded or Schlieren and that of the smectic mesophase is focal conic smectic A or C type. The transition curves of the phase diagram behave in a normal manner without the exhibition of an odd-even effect. Analytical and spectral data confirm the molecular structure of the homologs. Overall mesogenic phase temperature range varies from 11.0°C to 59.0°C. The average thermal stabilities of smectic and nematic are 122.25°C and 139.0°C, respectively. The series is predominantly nematogenic and partly smectogenic with a middle-ordered melting type and a considerable range of liquid crystallinity. Melting points and transition temperatures were determined using an optical polarizing microscope equipped with a heating stage. The mesomorphic properties are compared with structurally similar series.
- Chauhan,Doshi
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- Synthesis and Mesomorphic Phase Behavior of Laterally Substituted Novel Azoesters
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A novel homologous series of 4(4′-n-alkoxy benzoyloxy)phenylazo 2′′-chloro-3′′-methyl benzenes was synthesized and studied for mesophase behavior dependence on molecular structure. The nematogenic mesophase is exhibited from the first to the last member and the smectogenic mesophase from the hexyloxy to the tetradecyloxy member of the series. The nematic mesophase is of a threaded or Schlieren type, and the smectic mesophase is of a focal conic fan of the type A or C. Mesomorphic properties of the present novel homologous series are compared with other structurally similar homologous series.
- Khunt,Kotadiya,Bhoya
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- Synthesis and characterization of new nematic liquid crystalline compounds-based thiophene units
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Four new liquid crystalline thiophene compounds (M1-M4) with a long flexible spacer were prepared. Their structures were characterized by Fourier transform infrared and proton nuclear magnetic resonance. The mesomorphism and thermal stability were investigated with differential scanning calorimetry, polarizing optical microscopy, and thermogravimetric analysis. The photo-physical properties were evaluated using ultraviolet/visible spectroscopy and photoluminescence. M1-M4 all showed thermotropic mesogenic properties with excellent thermal stability, and exhibited nematic threaded texture, droplet texture, and Schlieren texture on heating and cooling cycles. The effect of flexible spacer and terminal groups on mesomorphic and spectroscopic property is discussed. The experimental results demonstrated that the tendency toward melting temperature (Tm) decreased, while isotropic temperature (Ti) increased with increasing the flexible spacer length. In CHCl3 solution, these thiophene compounds displayed an intense broad absorption band peaking within 230-340 nm and a maximum fluorescent emission wavelength at 426-439 nm.
- Jia, Ying-Gang,Su, Dong,Guo, Zhi-Hao,Hu, Jian-She
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- Mesomorphic properties of chiral nematic star-shaped liquid crystals containing melitose as cores
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Three star-shaped compounds (SSCs, c1-c3), are synthesized by using melitose as the chiral core and monacid (b1, b2 and b3) as side arms, respectively. The side arms (b1, b2 and b3), in which terminal chains are different, are introduced into the hydroxyl groups of melitose by esterification, respectively. The chemical structures of c1-c3 are confirmed by FT-IR and 1H NMR. The roles played by the chiral core and the side arms in the mesomorphic properties of the SSCs are studied. b1 is not a liquid crystal (LC), while b2 and b3 are nematic LCs. c1 is not a LC, while c2 and c3 are star-shaped LCs (SSLCs) and exhibit fingerprint texture of chiral nematic. c1, c2 and c3 are all levo-SSCs, which are different from their parent cores. The absolute value of their specific rotation increases with the increase of the terminal chain length of the side arms. The melting temperature of SSCs decreases with the increase of the terminal chain length of the side arms. For c2-c3, their mesomorphic region increases with the increase of the terminal chain length of the side arms. The results suggest that the LC properties of the side arms play an important role in inducing LC properties of the SSCs and the chiral core induces the chiral nematic of SSLCs, which contain the nematic LCs as the side arms.
- Tian, Mei,Zhang, Bao-Yan,Cong, Yue-Hua,He, Xiao-Zhi,Zhang, Bing
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- Mesomorphism dependence on molecular rigidity
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A novel ester homologous series of thermotropic liquid crystal (LC) has been studied with a view to understanding and establishing the relation between LC property and the molecular structure. The series consists of 11 members, the CCand Cmembers of the series are nonliquid crystals. LC properties commence from the Chomolog and continue up to the Chomolog as enantiotropic nematic and smectic in addition to nematic. Transition temperatures of the homologs were determined by an optical polarizing microscope equipped with a heating stage. Textures of nematic phase are threaded or Schlieren and that of smectic is focal conic of the type-A. Analytical and spectral data confirm the structures of homologs. Thermal stability for nematic is 93 °C and 136°C, respectively. The N-I and Sm-N transition curves of phase diagram do not exhibit odd-even effect. The N-I transition curve partly behaves in an abnormal manner. The Cr-I and Sm-N transition curves behave in normal manner. The LC behavior of the present series is compared with structurally similar known homologous series.
- Chauhan,Patel,Pandya,Doshi
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- Ni-Catalyzed Direct Carboxylation of Aryl C?H Bonds in Benzamides with CO2
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The direct carboxylation of inert aryl C?H bond catalyzed by abundant and cheap nickel is still facing challenge. Herein, we report the Ni-catalyzed direct carboxylation of aryl C?H bonds in benzamides under 1 atm of CO2 to afford various methyl carboxylates or phthalimides, dealing with different post-processing. The reaction displays excellent functional group tolerance and affords moderate to high carboxylation yields under mild conditions. Detail mechanistic studies suggest that a Ni(0)?Ni(II)?Ni(I) catalytic cycle may be involved in this reaction. (Figure presented.).
- Pei, Chunzhe,Zong, Jiarui,Li, Bin,Wang, Baiquan
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supporting information
p. 493 - 499
(2021/12/08)
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- Rh(iii)-Catalyzed three-component cascade annulation to produce theN-oxopropyl chain of isoquinolone derivatives
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Developing powerful methods to introduce versatile functional groups at theN-substituents of isoquinolone scaffolds is still a great challenge. Herein, we report a novel three-component cascade annulation reaction to efficiently construct theN-oxopropyl chain of isoquinolone derivativesviarhodium(iii)-catalyzed C-H activation/cyclization/nucleophilic attack, with oxazoles used both as the directing group and potential functionalized reagents.
- He, Yuan,Liao, Xian-Zhang,Dong, Lin,Chen, Fen-Er
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supporting information
p. 561 - 567
(2021/02/06)
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- Design and synthesis of N-(3-sulfamoylphenyl)amides as Trypanosoma brucei leucyl-tRNA synthetase inhibitors
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The protozoan parasite Trypanosoma brucei (T. brucei) causes human African trypanosomiasis (HAT), which is a fatal and neglected disease in the tropic areas, and new treatments are urgently needed. Leucyl-tRNA synthetase (LeuRS) is an attractive target for the development of antimicrobial agents. In this work, starting from the hit compound thiourea ZCL539, we designed and synthesized a series of amides as effective T. brucei LeuRS (TbLeuRS) synthetic site inhibitors. The most potent compounds 74 and 91 showed IC50 of 0.24 and 0.25 μM, which were about 700-fold more potent than the starting hit compound. The structure-activity relationship was also discussed. These compounds provided a new scaffold and lead compounds for further development of antitrypanosomal agents.
- Li, Zezhong,Xin, Weixiang,Wang, Qing,Zhu, Mingyan,Zhou, Huchen
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- Preparation method of polysubstituted diphenyl ketone
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The preparation method comprises the following steps: (1) a compound represented by the formula II and a compound shown III as a raw material; and synthesizing the compound as shown IV. (2) The compound of Formula IV is subjected to Fries rearrangement to produce a compound of Formula V. (3) A compound of Formula V is subjected to a halogenation reaction in contact with a halogenation reagent to prepare a multi-substituted diphenyl ketone represented by Formula I. Wherein, X is selected from H, F, Cl, Br, I. R1 Selected H from F Cl, Br I are RO selected R from H, C1 - C6. X is selected from F, Cl, Br, and i. The present invention is capable of improving the yield and selectivity of the target product.
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Paragraph 0054-0057
(2021/09/21)
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- Synthesis and molecular docking studies of some novel antimicrobial benzamides
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Common use of classical antibiotics has caused to the growing emergence of many resistant strains of pathogenic bacteria. Therefore, we aimed to synthesize a number of N-(2-hydroxy-(4 or 5)-nitrophenyl)benzamide derivatives as a new class of antimicrobial compounds. Moreover, our second goal is to predict the interaction between active structures and enzymes (DNA –gyrase and FtsA) in the binding mode. In this study, thirteen N-(2-hydroxy-(4 or 5-nitrophenyl)-substituted-benzamides were synthesized and determined for their antimicrobial activity using the microdilution method. According to this work, none of the compounds showed any activity against Candida albicans and its clinical isolate. Some of the benzamides (4N1, 5N1, 5N2) displayed very significant activity against Staphylococcus aureus and MSSA with 4 μg/ml MIC value, even they were found to be more potent than ceftazidime. 4N1 was also found to be more effective than gentamicin against Enterococcus faecalis clinical isolate. Molecular docking studies revealed that 4N1, 5N1, and 5N2 showed a good interactions with DNA-gyrase. Moreover, 5N1 has interacted with FtsA enzyme in the binding mode, as well. Only compound 5N4 displayed very good activity against Escherichia coli ATCC 25922. These findings showed us that 4N1, 5N1, 5N2, and 5N4 could be lead compounds to discover new antibacterial candidates against multidrug-resistant strains.
- Acar, Cemre,Yal??n, Gozde,Ertan-Bolelli, Tu?ba,Kaynak Onurda?, Fatma,?kten, Suzan,?ener, Funda,Y?ld?z, ?lkay
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- Discovery of methoxy-naphthyl linked N-(1-benzylpiperidine) benzamide as a blood-brain permeable dual inhibitor of acetylcholinesterase and butyrylcholinesterase
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The cholinesterase enzymes play a vital role in maintaining balanced levels of the neurotransmitter acetylcholine in the central nervous system. However, the overexpression of these enzymes results in hampered neurotransmission. Both the major forms of cholinesterase enzymes viz. acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) play a crucial role in blocking neurotransmission; therefore, in recent years, a strategy of dual cholinesterase inhibition is being explored. Herein, we developed an energy-optimized e-pharmacophore hypothesis AHHPRR from AChE-donepezil complex and screened a set of 15 scaffolds that were designed imaginarily. The ligand with N-(1-benzylpyridinium) benzamide framework has shown the highest fitness and volume score, which was chosen for synthesis and validation. A series of pyridinium benzamides were synthesized and screened for cholinesterase inhibition that led to the identification of 7b, a naphthalene containing N-(1-benzylpiperidine) benzamide as a potent dual AChE and BChE inhibitor with IC50 values of 0.176, and 0.47 μM, respectively. The kinetic study indicated that 7b inhibits AChE in a non-competitive manner with Ki value of 0.21 μM, and BChE in a mixed-fashion with Ki of 0.15 μM. The observed mode of inhibition was corroborated with molecular docking studies. The MD simulation studies pointed out that both AChE and BChE undergo low conformational changes in complex with 7b. The benzamide 7b displayed high BBB permeability in PAMPA assay, which indicates its potential for further exploration in preclinical studies for Alzheimer's disease.
- Abdullaha, Mohd,Bharate, Sandip B.,Nuthakki, Vijay K.
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- Synthesis and characterization of novel rod-like ester-based liquid crystalline homologous series: Effect of tert-butyl tail on mesomorphism
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A new rod-like homologous series consisting twelve compounds with central ester linkage and terminal tert-butyl group, tert-butyl [4-(4’-n-alkoxybenzoyloxy)benzoates] has been synthesized and characterized through standard spectroscopic techniques like UV, FT-IR, 1HNMR, DSC, POM, and XRD. Methoxy and ethoxy derivatives are nonmesogenic. Nematic mesophase commences as enantiotropy from propyloxy derivative and persists up to the octadecyloxy derivatives. Smectic A mesophase commences as monotropy from propyloxy to the octadecyloxy derivatives. The mesomorphic properties of present series are compared with other structurally related series to evaluate the effect of terminal tert-butyl group on mesomorphism. Two derivatives are subjected to in?vitro antimicrobial activity.
- Thakur, Shavi,Patel, Hemant N.
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- Dependence of mesomorphism on terminal polar group in novel azoester series
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Novel homologous series 4-(4′-n-alkoxy benzoyloxy) napthyl azo 4″–bromo benzenes, consisted of 11 members of a series. All the 11 members (ethoxy to hexadecyloxy) except hexadecyloxy are only enantiotropically nematogenic without exhibition of any smectogenic character. Transition temperatures and the textures are determined by an optical polarizing microscopy equipped with a heating stage. Textures of a nematic phase are threaded or schlieren. Analytical and spectral data supported the molecular structure of homologs. Transition curves viz., solid-nematic and nematic-isotropic showing phase behavior of the mesophase in a phase diagram behave in normal manner. Alternation of transition temperatures is exhibited by N–I transition curve. Thus, novel series is entirely nematogenic and high ordered melting type. Thus, synthesis of a novel azoester homologous series is carried out with a view to understand and establish the effect of molecular structure on Liquid crystal (LC) behaviors of a substance.
- Kher, Seema N.,Prajapati,Makwana,Chandra, Raviprakash S.
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- Identification of Anti-Mycobacterial Biofilm Agents Based on the 2-Aminoimidazole Scaffold
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Tuberculosis (TB) remains a significant global health problem for which new therapeutic options are sorely needed. The ability of the causative agent, Mycobacterium tuberculosis, to reside within host macrophages and form biofilm-like communities contributes to the persistent and drug-tolerant nature of the disease. Compounds that can prevent or reverse the biofilm-like phenotype have the potential to serve alongside TB antibiotics to overcome this tolerance, and decrease treatment duration. Using Mycobacterium smegmatis as a surrogate organism, we report the identification of two new 2-aminoimidazole compounds that inhibit and disperse mycobacterial biofilms, work synergistically with isoniazid and rifampicin to eradicate preformed M. smegmatis biofilms in vitro, are nontoxic toward Galleria mellonella, and exhibit stability in mouse plasma.
- Nguyen, T. Vu,Minrovic, Bradley M.,Melander, Roberta J.,Melander, Christian
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p. 927 - 937
(2019/03/26)
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- Study of Y-shaped liquid crystalline materials with polar nitro substituent
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A new homologous series of Y-shaped liquid crystals namely 4-Nitro-[2′4′bis (4″-n-alkoxybenzoyloxy)] phenyl bisazobenzenes have been synthesized and its thermotropic properties studied on the hot stage of a polarizing microscope. The compounds consist four phenyl rings joined through ester and bisazo linkages with alkoxy and nitro as terminal substituents. The structures of synthesized compounds were confirmed by spectroscopic techniques such as FTIR, 1HNMR as well as elemental analysis. The compounds were found to exhibit enantiotropic nematic and smectic mesophases. The role of molecular shape, size and polarity of functional groups in the mesophases formation is discussed.
- Dixit, Sandhya
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- Mesomorphism dependence on terminal polar group in the nonlinear novel azoester series
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Synthesis of a novel azoester homologous series is carried out with a view to understand and establish the effect of molecular structure on liquid crystal (LC) behaviors of a substance. Novel series consists of ten LC substances. All the homologs are enantiotropically nematogenic without exhibition of smectic property. Transition and melting temperatures, textures of LC are determined by an optical polarizing microscopy equipped with a heating stage. Textures of nematic phase are threaded or schlieren. Transition curves of a phase diagram behaved in normal manner. Nematic–isotropic transition curve exhibited odd–even effect. Analytical and spectral data supported and confirmed the structures of homologues.
- Kher, Seema N.,Prajapati,Chandra, Raviprakash S.,Makwana
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- Dependence of mesomorphism on geometrical shapes of isomeric and nonisomeric series of chalconyl esters
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A meta substituted chalconyl ester homologous series: RO?C6H4?COO?C6H4(meta)?CO?CH?CH?C6H4?OC12H25(n)(para) is synthesized and studied with a view to understanding the effect of molecular substitution at meta position in a molecular structure on thermotropic liquid crystal properties. The novel homologous series consists of thirteen homologues (C1 to C18). All the homologues except the nonliquid crystal homologues C1, C2, C3 are enantiotropic nematic with the absence of smectic properties. The transition and melting temperatures were determined by an optical polarizing microscopy (POM) equipped with a heating stage. Textures of a nematic phase are threaded or Schlieren. Transition curves (Cr-N/I and N-I) behave in normal manner except homologues between C10 and C14 of N-I curve, which show negligible deviation from normal and a smooth descending tendency. The N-I transition curve exhibits an odd-even effect up to C10 homologue and then the odd-even effect disappears for higher homologues. Analytical and the spectral data support the molecular structures. Thermal stability for nematic is 107.3°C and the mesophase lengths range between 13.0°C and 35.0°C at the C18 and C12 homologues respectively. Group efficiency order for nematic is derived on the basis of thermal stability as ?OC12H25(n) (linear) > ?OC12H25(n) (nonlinear) > ?OC16H33 (nonlinear).
- Patel, Priya K.,Shah
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p. 168 - 177
(2017/03/08)
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- Palladium-Nanoparticles-Catalyzed Oxidative Annulation of Benzamides with Alkynes for the Synthesis of Isoquinolones
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A novel method to synthesize isoquinolones via oxidative annulation of N-alkoxy benzamides and alkynes using binaphthyl-stabilized palladium nanoparticles (Pd-BNP) as catalyst has been developed. This methodology affords various isoquinolone derivatives in good to excellent yields with high regioselectivities in the presence of air as oxidant. N-Methoxybenzothioamide was also found to undergo oxidative annulation with alkyne successfully and provided a sulfur analogue of isoquinolones in moderate yields. The Pd-BNP catalyst was easily recovered and reused up to four times without any apparent agglomeration. (Figure presented.).
- Sharma, Nidhi,Saha, Rajib,Parveen, Naziya,Sekar, Govindasamy
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supporting information
p. 1947 - 1958
(2017/06/09)
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- Iron-catalyzed C-H/N-H activation by triazole guidance: Versatile alkyne annulation
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Iron-catalyzed C-H/N-H functionalizations were achieved by the aid of modular triazole amides. The alkyne annulation allowed for the expedient synthesis of valuable isoquinolone scaffolds with high levels of chemo-, site- and regio-selectivities.
- Cera,Haven,Ackermann
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supporting information
p. 6460 - 6463
(2017/07/10)
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- Design, Synthesis, and Biological Evaluation of Tetrahydroisoquinoline-Based Histone Deacetylase 8 Selective Inhibitors
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Histone deacetylase 8 (HDAC8) is a promising drug target for multiple therapeutic applications. Here, we describe the modeling, design, synthesis, and biological evaluation of a novel series of C1-substituted tetrahydroisoquinoline (TIQ)-based HDAC8 inhibitors. Minimization of entropic loss upon ligand binding and use of the unique HDAC8 "open" conformation of the binding site yielded a successful strategy for improvement of both HDAC8 potency and selectivity. The TIQ-based 3g and 3n exhibited the highest 82 and 55 nM HDAC8 potency and 330- and 135-fold selectivity over HDAC1, respectively. Selectivity over other class I isoforms was comparable or better, whereas inhibition of HDAC6, a class II HDAC isoform, was below 50% at 10 μM. The cytotoxicity of 3g and 3n was evaluated in neuroblastoma cell lines, and 3n displayed concentration-dependent cytotoxicity similar to or better than that of PCI-34051. The selectivity of 3g and 3n was confirmed in SH-SY5Y cells as both did not increase the acetylation of histone H3 and α-tubulin. Discovery of the novel TIQ chemotype paves the way for the development of HDAC8 selective inhibitors for therapeutic applications.
- Taha, Taha Y.,Aboukhatwa, Shaimaa M.,Knopp, Rachel C.,Ikegaki, Naohiko,Abdelkarim, Hazem,Neerasa, Jayaprakash,Lu, Yunlong,Neelarapu, Raghupathi,Hanigan, Thomas W.,Thatcher, Gregory R. J.,Petukhov, Pavel A.
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supporting information
p. 824 - 829
(2017/08/16)
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- Merging gold catalysis, organocatalytic oxidation, and Lewis acid catalysis for chemodivergent synthesis of functionalized oxazoles from: N -propargylamides
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Novel catalytic systems consisting of cationic gold complexes, N-hydroxyphthalimide (NHPI), and transition-metal-based Lewis acids have been developed for the one-pot synthesis of functionalized oxazoles from N-propargylamides with excellent functional group tolerance. These transformations demonstrated the excellent compatibility of homogeneous gold catalysis with organocatalytic oxidative carbon-nitrogen bond formations using tert-butyl nitrite as the terminal oxidant. Moreover, oxazolecarbonitriles or carboxamides can be easily synthesized in a one-pot protocol according to the different synthetic requirements.
- Mai, Shaoyu,Rao, Changqing,Chen, Ming,Su, Jihu,Du, Jiangfeng,Song, Qiuling
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supporting information
p. 10366 - 10369
(2017/09/25)
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- Subtle side-chain tuning on terminal groups of small molecule electron acceptors for efficient fullerene-free polymer solar cells
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Four dithienoindaceno[1,2-b:5,6-b′]dithiophene (DT-IDT) based small molecules IT-O1, IT-O2, IT-O3 and IT-O4 with increasing alkoxyl chain length from methoxy to butoxy on the terminal-groups were synthesized to investigate the end-group side-chain effects on these acceptor-donor-acceptor-type small molecule electron acceptors. The optical absorption and energy levels of the four molecules, blend morphologies, carrier mobilities, and photovoltaic performances of the devices blended with the polymer PBDB-T are systematically investigated. Interestingly, both the solubility and electron mobility are enhanced for these materials with decrease in side chain length, which lead to ideal morphologies and balanced charge transport. Hence, increased Jsc and FF, and thus distinctly higher PCEs of 11.6% were obtained from the PBDB-T:IT-O1-based devices.
- Zhu, Jie,Li, Sunsun,Liu, Xiaoyu,Yao, Huifeng,Wang, Fenghao,Zhang, Shaoqing,Sun, Mingliang,Hou, Jianhui
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p. 15175 - 15182
(2017/08/01)
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- Mesomorphism dependence on central bridge (-COO-CH2-) and terminal end group (-Br)
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A novel series of liquid crystalline (LC) ester materials has been synthesized and studied with a view to understanding the effects of molecular structure on LC behavior. The homologous series of eleven members is entirely enantiotropically smectogenic without exhibition of a nematic phase. Transition temperatures and the texture of smectic phase was determined by an optical polarizing microscope equipped with a heating stage (POM). Transition curves (Cr-Sm and Sm-I) showing phase behavior in a phase diagram behave in a normal manner. Textures of smectic phase are focal conic fan shaped of the type Smectic-A or Smectic-C. An odd-even effect is exhibited by the Sm-I transition curve. The average thermal stability for smectic is 91.2°C and the mesogenic phase length ranges between 3.6°C and 39.3°C. Thus, the novel smectogenic homologous series is a middle-ordered melting type whose LC phase is relatively middle ordered. The LC properties of the present series are compared with a structurally similar homologous series. Analytical and spectral data support the molecular structures.
- Marathe, Rajesh B.,Doshi
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p. 122 - 131
(2016/02/19)
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- Dependence of liquid crystallinity on molecular rigidity
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A novel homologous series of liquid crystals (LC) of chalconyl derivatives is synthesized and studied with a view to understanding and establishing the effects of molecular structure on liquid crystal properties. The novel series consists of 12 homologues. Nematogenic LC property commences from C3 and continues up to C14 and the smectogenic mesophase is exhibited from C4 to C16. The C3 homologue is a monotropic nematic and the rest of the homologues are enantiotropically smectic and nematic or only smectic (C16). Transition curves Cr-Sm, Sm-N, Cr-I, and N-I behave in normal manner with exhibition of odd-even effect, showing phase behaviors of the series.
- Rakhasia,Bhoya
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- Study of mesomorphism and its relation to molecular structure with special reference to central bridges viz. -COO- and -CH=CH-COO- of the homologous series
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Two ester homologous series of mesogens, viz., Methyl-p-(p′-n-alkoxy benzoyloxy) cinnamates (X) and Methyl-p-(p′-n-alkoxy cinnamoyloxy) cinnamates (Y) being structurally similar are discussed. Both (X) and (Y) differ in respect of central bridges linking two phenyl rings. Only enantiotropic nematogenic character is observed without exhibition of any smectic character by all members of series (X) and (Y). Thermal stability of series (X) is relatively low as compared to (Y), but nematogenic mesophase lengths are of reverse order. Solid-nematic/solid-isotropic and nematic-isotropic transition curves in the phase diagrams behave in normal manner.
- Sharma,Solanki,Patel,Patel
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p. 137 - 145
(2016/03/01)
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- Mesomorphism of azo-esters and chalcone-esters
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AOne chalcone-ester homologous series of mesogens α-4-[4/-n-alkoxybenzoyloxy phenyl β-4//methoxy benzoyl ethylenes (A) and one azo-ester homologous series of mesogens p-(p/-n-alkoxybenzoyloxy) phenyl azo-p//-methoxy benzene (B) being structurally similar are discussed. Both series (A) and (B) differ in respect of central bridges linking two phenyl rings. Mesomorphic properties start from 6th and 1st member of series (A) and (B) respectively. In series (A), 6th to 12th members show both smectogenic and nematogenic properties, and the 14th and 16th members show only nematogenic property. While in series (B), 1st to 10th members show nematogenic properties, 11th member shows both smectogenic and nematogenic properties, while 12th member shows only smectogenic property. Thermal stability of series (A) is relatively high as compared to series (B). Transition temperatures are observed through hot stage polarizing microscope by the miscibility method. Analytical data support the structure of molecules. Textures of series (A) in nematic are threaded and Schlieren in SmecticSmectic A type, while that of series (B) in nematic are threaded in SmecticSmectic A and smectic C.
- Jain,Sharma, Vinay S.,Chauhan,Patel
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p. 102 - 111
(2016/07/14)
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- Mesomorphism dependence on lateral substitution of functional groups and their position in series: 4(4'-n-alkoxy benzoyloxy)-3-chloro phenyl azo-2"-methoxy benzenes
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Eleven homologues of the title series were synthesized. The methyl-to-pentyl derivatives are nonmesomorphic. The nematic mesophase commences from the sixth member of the series without any smectic phase. An odd-even effect in the nematic-isotropic transition curve is not observed. The nematic mesophase appeared as a threaded or a Schlieren-type texture as observed through a hot-stage polarizing microscope. The nematic-isotropic transition temperatures are between 89°C and 127°C with the mesomorphic range varying from 9°C to 44°C at the hexyl and tetradecyl derivative of the series, respectively. The nematic-isotropic transition curve initially rises and then falls in a normal manner as the series is ascended, but it abnormally rises beyond the 10th homologue. The series is enantiotropic nematic with a middle-ordered melting type. Analytical data support the structures of the molecules. The thermal stability and some other mesomorphic characteristics are compared with structurally similar homologous series. The average nematic-isotropic thermal stability is 105.4°C.
- Patel,Prajapati,Doshi
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- Synthesis of novel ester series and study of its mesomorphism dependence on terminal end group with lateral-OCH3 group
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Novel liquid crystal (LC) materials of ester derivatives were synthesized and studied with a view to understanding and establishing the effects of molecular structure on LC properties. The novel molecules consist of two phenyl rings bonded through-COO-central group and a laterally substituted methoxy group with-OCnH2n+1 as well as-COOCH3 terminal end groups, and yielded 12 homologous members of an ester series. The C1 to C3 members are nonmesomorphic, the C4 to C12 members are enantiotropic nematic only, and the C14 to C16 members are enantiotropically smectogenic in addition to nematogenic. Transition temperatures and the textures of LC state were observed through an optical polarizing microscope (POM) equipped with a heating stage. The textures of nematic phase are threaded or Schlieren, and that of smectic phase are focal conic of the type A or C. Transition curves of a phase diagram behave in normal manner with the exhibition of an odd-even effect (only N-I). Analytical and spectral data support the molecular structures of the novel ester derivatives. The LC properties of the present series are compared with structurally similar other known series. The average thermal stability of the series is 93°C for smectic and 120.88°C for nematic and the mesogenic phase length ranges between 2°C and 46°C.
- Vadodaria,Ladva,Doshi,Travadi
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- Synthesis of novel azoester homologous series of liquid crystalline behavior and the study of mesomorphism dependence on lateral substitution of middle phenyl ring
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The titled azoester liquid crystalline homologous series consists of eleven homologues. The pentyl to tetradecyl derivatives of the series are nematogenic without exhibition of smectogenic character. Rest of the members of the series are nonliquid crystalline in nature. Textures of the nematic mesophase are schlieren or threaded type. Transition curves in the phase diagram showed normal phase behavior. Transition temperatures and liquid crystal behavior observed under an optical polarizing microscope equipped with a heating stage. An odd even effect is observed for nematic-isotropic transition curve. Analytical and spectral data confirms the structures of the molecules. Present homologous series is predominant nematogenic and partly nonmesogenic. Average thermal stability for nematic is 125.33°C and nematogenic mesophase length varies between 12°C to 48°C at tetradecyl (C14) and octyl (C8) derivatives, respectively.
- Patel,Doshi, Ankita A.,Prajapati,Doshi
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- Mesomorphism dependence on lateral substitution and central bridge
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A novel ester homologous series was synthesized and studied with a view to understanding and establishing the effects of molecular structure on liquid crystal properties with a common laterally substituted-OCH3 group and changing terminal groups. The novel series consists of twelve members. The C1 to C3 members are not liquid crystals and the rest of the members C4 to C16 are smectogenic without exhibition of nematic character. Textures of smectic phase are focal conic fan shaped of the type A or C. The transition temperatures and textures of smectic mesophases were observed through hot stage polarizing microscopy (POM). The transition curves (Cr-I or Cr-M and Sm-I) behaved in normal manner. Analytical and spectral data support the molecular structures. Average thermal stability for smectic is 77.25°C and smectogenic mesophase ranges from 15°C to 33°C. Liquid crystal properties of the present series are compared with structurally similar homologous series. Thus, the series is smectogenic only with three homologs nonmesogenic.
- Vadodaria,Ladva,Doshi,Travadi
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p. 103 - 111
(2016/02/19)
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- Dependence of mesomorphism on tail group in combination with a lateral methoxy group
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A novel homologous series of esters with a lateral methoxy group and terminal n-heptyl cinnamate group was synthesized and studied to investigate mesomorphic behavior in relation to structure. The twelve membered series consists of methoxy to pentyloxy derivatives that are nonmesomorphic and the rest of the homologs as smectegenically mesomorphic, including C6 and C7 monotropic smectic and C8 to C16 enantiotropic smectic without exhibition of any nematic property. The textures of smectogenic mesophases are focal conic fan shaped or batonates of the type smectic-A or Schlieren-C. An odd-even effect is exhibited by the Sm-I transition curve in the phase diagram. The Cr-Sm and Sm-I transition curves behave in a normal manner. Transition temperatures and textures were determined on an optical polarizing microscope, equipped with a heating stage. Some representative members were characterized by IR, H1NMR, mass spectra, and elemental analysis. Analytical data support the molecular structures of the homologs. Mesomorphic properties of the present novel series are compared with the structurally similar known series. The present series is smectogenic only, whose thermal average stability is 89.8°C and of a middle-ordered melting type.
- Travadi,Vadodaria,Ladva,Doshi
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- Mesomorphism dependence on molecular rigidity with reference to -CH=CH- unit of central bridge
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A novel ester homologous series of rich mesomorphism and low temperatures with unexpected phase behaviors of eleven homologues was synthesized and studied with a view to understanding and establishing the relation between mesomorphic behaviour and the molecular structure of a series 4-(4′-n-alkoxybenzoyloxy)-4″-chlorobenzyl cinnamates. All the members of the novel series are enantiotropically smectogenic and the octyloxy (C8) to hexadecyloxy (C16) homologues are enantiotropically nematogenic, in addition to smectogenic. Odd-even effect is observed for Sm-I/Sm-N transition curve but it is absent for N-I transition curve. Textures of nematic phase are threaded or Schlieren and that of the smectic phase are fan shaped or batonates of smectic-A type phase or Smectic-C type for C16 homologues as judged directly from a heating stage of an optical polarizing microscopy. Analytical and spectral data confirmed the molecular structures of novel homologues. Mesomorphic properties of present series are compared with the structurally similar other known series. The average smectic and nematic thermal stabilities are 92.78°C and 100.8°C, respectively. Mesophase length minimum to maximum for smectic and nematic are 21.0°C to 31.1°C and 8.4°C to 42.6°C respectively. Thus, the present novel series is partly nematogenic and fully smectogenic with considerable degree of mesomorphism and low melting type.
- Marathe,Doshi
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- Mesomorphism Dependence on Molecular Structure
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A novel homologous series of liquid crystal (LC) derivatives of general structure: RO·C6H4·COO·C6H3·OCH3(ortho)CH = CH·COO·(n)C5H11 was synthesized and studied with a view to understanding the effect of molecular structure on liquid crystal behavior with reference to lateral-OCH3 and terminal end group. Homologous series consists of 12 derivatives (C1-C16), the first five (C1-C5), and the last (C16) members are not liquid crystals and the rest of the homologs (C6-C14) are enantiotropically smectogenic without exhibition of the nematic phase. The textures of the smectic phases are focal conic fan shaped or batonets of smectic-A or smectic-C. Average thermal stability for smectic is 81.8°C and mesophase length ranges from 9°C to 31°C. Transition curves of a phase diagram (Sm-I and Cr-Sm/I) behave in a normal manner. The Sm-I transition curve exhibits an odd-even effect. Analytical and spectral data support the molecular structures. The series is smectogenic of a middle ordered melting type. LC properties of the present series are compared with structurally similar known homologous series. Transition temperatures were determined by an optical polarizing microscope equipped with a heating stage.
- Travadi,Vadodaria,Ladva,Doshi
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- Dependence of Mesomorphism on Molecular Rigidity with Reference to Lateral Substitution and Central Bridge
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A novel mesogenic ester homologous series is synthesized and studied with a view to understanding and establishing the effect of laterally substituted-OCH3 on mesomorphic behavior. The series consists of twelve members. C1 to C4 members are nonmesogenic, C6 to C12 are smectogenic in addition to nematogenic, and C14 to C16 are only smectogenic. The textures of smectic and nematic phases are A or C type and threaded or Schlieren, respectively. The transition curves in a phase diagram exhibit an odd-even effect and behave in normal manner except for the C14 and C16 derivatives in Sm-I transitions. Thermometric data were determined by an optical polarizing microscope equippedwith a heating stage. Average thermal stability for smectic and nematic are 107.7°C and 121.0°C, respectively. Smectogenic and nematogenicmesophase length ranges from 11.0 to 44.0°C and 12.0°C to 39.0°C, respectively. The mesomorphic properties of present series are comparedwith structurally similar other known series. Thus, present series is predominantly smectogenic and partly nematogenic ofmiddle ordered melting type.
- Travadi,Vadodaria,Ladva,Doshi
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- Mesomorphism Dependence of Chalconyl Derivatives on Position of -CH=CH- Unit
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A novel homologous series of heterocyclic chalconyl esters (C1 to C16) has been synthesized and studied with a view to understanding and establishing the effects of molecular structure on liquid crystal (LC) properties and the degree of liquid crystallinity. The C1 to C6 homologues are not liquid crystals, the C7 homologue is enantiotropic nematic, the C8 to C16 homologues are smectogenic in addition to nematogenic (C8 & C10 monotropic smectic). The texture of nematic phases are threaded or Schlieren and that of the smectic phase are fan-shaped smectic-A or smectic-C type. Transition temperatures and the textures of mesophases were determined by an optical polarizing microscope equipped with a heating stage. Transition curves Cr-I/M, Sm-N/N-Sm, and N-I showing phase behaviors of series in a phase diagram behave in normal manner. Thermal stability for smectic and nematic are 115.66°C and 126.83°C and their mesophase lengths minimum to maximum are 6.3 to 12.9°C and 6.9°C to 17.4°C, respectively. Analytical and spectral data confirms the molecular structures of homologues. LC properties of present novel series are compared with structurally similar other reported series.
- Rakhasia,Bhola,Bhoya
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- Study of the Effect of Lateral Substitution on Mesogenic Behavior with Reference to -CH=CH- Unit
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A novel cinnamate ester homologous series has been synthesized and studied with a view to understanding and establishing the effects of molecular structure on liquid crystal (LC) properties with a focus on the highly polar methoxy group as a lateral substituent. The series consists of twelve homologs; of which C1-C5 are nonmesogenic, and the rest of the homologs are enantiotropically smectogenic or and nematogenic. The texture of nematic phases is threaded or Schlieren and that of the smectic is either smectic A or C, as recognized and determined through an optical polarizing microscope equipped with a heating stage. The Sm-N I and N-I transition curves exhibit odd-even effects and behave in normalmanner. The Cr-IMbehaves in normalmanner. Analytical and spectral data confirm the molecular structures of homologs. The average thermal stabilities for smectic and nematic are 125.3 C and 129.8 C, respectively, whose total mesophase length varies from 13 C to 51 C. Some LC properties of present series are compared with the structurally similar known series.
- Travadi,Vadodaria,Ladva,Doshi
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- Mesomorphism dependence on molecular flexibility
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A novel ester homologous series of liquid crystals with a highly polar laterally substituted –OCH3 group is synthesized and studied with a view to understanding and establishing the effects of molecular structure involving lateral substitution on liquid crystal behavior. The novel series RO·C6H4·COO·C6H3·OCH3(ortho)CH=CH·COO·C2H5 consists of 12 homologs of which C7, C8, C10 are nematogenic and C12, C14, C16 homologs are smectogenic. The rest of the homologs are nonliquid crystals. The textures of nematic phase are threaded and the smectic phase is of the type A or C. Transition temperatures and the textures of mesophases were determined by an optical polarizing microscope equipped with a heating stage. Analytical and spectral data support the molecular structures. The N-I and Sm-I transition curves behave in normal manner without exhibition of an odd-even effect. Average thermal stability for smectic and nematic are 127.3°C and 129°C, respectively. The total mesophase length ranges from 17°C to 57°C and series is of a middle ordered melting type with transition temperatures varying between 82°C and 148°C. The liquid crystal properties of present novel series are compared with, structurally similar known homologous series.
- Travadi,Vadodaria,Ladva,Doshi
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- Mesomorphism dependence on tail group
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A chalconyl homologous novel series of thermotropic liquid crystals (LC) have been synthesized and studied with a view to understand and establish the effects of molecular structure on LC properties in thermotropic behaviors. Homologous series RO-C6H4-COO-C6H4-CO-CH=CH-C6H4-OC14H29 consists of 13 homologs (C1–C18), C1–C6 homologs are nonliquid crystals and the rest of the homologs are enantiotropically nematogenic without exhibition of smectic property. Transition temperatures and the textures of the nematic phase were determined by an optical polarizing microscopy, equipped with a heating stage. Texture of a nematic phase are threaded or schlieren. The Spectral and analytical data confirms the molecular structures of homologs. Thermal stability for nematic is 123.0°C and its mesogenicphaselength ranges between 13°C and 34°C. Cr-N/I and N-I transition curves behaved in normal manner except C14 homolog which shows negligible abnormality for N-I transition temperature or curve with exhibition of odd-even effect. Some LC properties are compared with the structurally similar homologous series. Thus, present homologous series is nematogenic and middle ordered melting type.
- Jain,Patel
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p. 121 - 129
(2016/07/14)
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- Dependence of thermotropic mesomorphism on flexible tail group
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A novel homologous series RO-C6H4-COO-C6H4-CO-CH:CH-C6H4-OC12H25 of chalcones have been synthesized and studied with a view to understand and establish the effects of molecular structure on liquid crystal (LC) properties of a substance. Liquid crystal properties of a novel series commences from C6 homologue and continue upto the last C18 homologue derivative of a series, as enantiotropically nematogenic without exhibition of smectogenic characteristic. The rest of the homologues (C1 to C5) are nonliquid crystals (NLC). Transition temperatures of homologues (C1 to C18) are determined by an optical polarizing microscopy equipped with a heating stage. Textures of a nematic phase are threaded or schlieren. Transition curves of a phase diagram behaved in normal manner except for C18 member of a series, which drastically behaved with abnormal manner. N-I transition curve exhibits odd–even effect. Average thermal stability for nematic is 110.25°C and mesophase length ranges from 10°C to 39°C. Analytical and spectral data supported the molecular structures of homologues. LC properties of present novel series are compared with structurally similar other known homologous series. Thus, present novel series of chalcones is partly nematogenic and of middle-ordered melting type.
- Patel, Priya K.,Shah
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p. 130 - 138
(2016/07/14)
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- Study of novel thermotropic liquid crystals with lateral nitro substituent
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In this article, we report synthesis and characterization of a novel thermotropic liquid crystals, namely, 4-bromo-[3′-nitro-4′(4″-n-alkoxybenzoyloxy)] phenyl azobenzenes. The first member of a homologous series is nonmesogenic in nature. The n-ethyl to n-decyl homologues exhibit enantiotropic nematic mesophases, while the n-dodecylton -hexadecyl homologues exhibit only smectic mesophases. The synthesized compounds were characterized by a combination of elemental analysis and standard spectroscopic methods. The mesogenic behavior of present series is explained by comparing each homologue of the related mesogenic series. The impact of the lateral nitro group on mesomorphism is also discussed.
- Dixit,Intwala
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- Dependence of thermotropic mesomorphism on molecular flexibility of changing tail group
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A novel chalconyl ester homologous series of liquid crystals has been synthesized and studied with a view to understanding and establishing the effect of molecular structure on liquid crystalline properties. Novel series consisted of 13 members (C1–C18) of a series. C1–C4 member of a series is nonliquid crystals and, the rest of the homolog members (C5–C18) are enantiotropically nematogenic with absence of smectogenic property. None of the homolog is monotropically mesomorphic. Transition and melting temperatures were determined by an optical microscope equipped with a heating stage. Textures of nematic phase are threaded or schlieren. Spectral and analytical data of selected members of a series confirms the molecular structures of homologues. Cr-N and N-I transition curves of a phase diagram behaved in normal manner with exhibition of odd-even effect of very short range as observed for N-I transition curve. Thermal stability for nematic is 122.0°C and the nematogenic mesophase ranges from 7.0°C to 38.0°C. Liquid crystal properties of a present series are compared with the structurally similar known homologous series.
- Solanki, Ravindra,Sharma, Vinay,Patel, Roshan
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p. 107 - 115
(2016/07/21)
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- Mesomorphism dependence on the combined effect of molecular rigidity and flexibility
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A novel liquid crystalline (LC) homologous series of azoesters with a laterally substituted methoxy group RO-C6H4-COO-C6H3-(-OCH3)-N═N-C6H4-COO-C4H9(n) has been synthesized and studied with a view to understanding the effect of molecular structure on thermotropic mesomorphism. The novel homologous series consists of thirteen homologues (C1–C18). The C1–C5 homologues are nonliquid crystals. The C6 and C7 homologues are only enantiotropically nematogenic and the rest of the mesomorphic homologues (C8–C18) are enantiotropically smectogenic and nematogenic. Transition temperatures and the textures of the mesophases were determined using an optical polarizing microscope (POM) equipped with a heating stage. The novel azoester homologues were characterised and confirmed using their analytical, spectral and thermometric data. Transition curves Cr-M/I, Sm-N and N-I behaved in normal manner without (Sm-N) and with (N-I) exhibition of odd-even effect respectively in a phase diagram. Thermal stabilities for smectic and nematic are 100.0°C and 127.7°C whose, mesomorphic phase length vary from 13.0°C to 24.0°C and 11.0°C to 33.0°C, respectively. The mesomorpism is compared with other known series.
- Jadeja,Patel
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- Mesomorphism dependence on molecular flexibility in an azoester series
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A novel azoester homologous series with a flouro terminal end group was synthesized and evaluated for mesomorphic properties. The novel homologous series consists of 12 members. The first two-third members of the series are nonmesogenic. The butyloxy to decyloxy homologues are enantiotropic nematogenic and the rest of the mesogenic homologoues are enantiotropic smectogenic only. Transition temperatures and textures of the mesophases were observed through an optical polarizing microscope equipped with a heating stage. The textures of the nematic phase are threaded or Schlieren as judged by a miscibility method and those of the smectic phase are of the type A or C. A phase diagram is used to illustrate the mesomorphic behavior across the series. Analytical and spectral data confirm the molecular structures of the homologues. Thermal stabilities of smectic and nematic mesophases are 114.3°C and 137.0°C respectively. The mesogenic phase lengths for smectic and nematic are vary from 8°C to 26°C and 26°C to 43°C respectively.
- Bhola,Nakum, Kiran,Karia, Kaushal,Bhoya
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p. 125 - 134
(2015/03/18)
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- Mesomorphism in relation to molecular structure with reference to a laterally substituted homologous series
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A novel homologous series 4-(4′-n-alkoxy benzoyloxy) 3-methyl phenyl azo-2″, 6″-dimethyl benzenes consists of 12 homologues. The methyl to hexyl derivatives are non-mesomorphic and the rest of the homologues are mesomorphic. Mesomorphism commences from heptyl homologue in a monotropic manner and continues as an enantiotropic nematic for octyl to dodecyl derivatives, and then monotropic mesomorphism as a nematic mesophase reappears for tetradecyl and hexadecyl derivatives without the exhibition of smectogenic character. The textures of the nematic mesophase are threaded, or are schlieren in type. The nematic-isotropic (or vice versa) transition curve of the phase diagram behaves in a normal manner without the exhibition of an odd-even effect. The average thermal stability for nematic to isotropic transition is 126.5°C. Analytical and spectral data confirm the structure of molecules. The mesomorphic to isotropic transition temperatures vary between 56°C and 130°C. The nematogenic mesophase appeared at the lowest temperature of 41.3°C. Transition and melting temperatures are determined using an optical polarizing microscopy equipped with a heating stage. The present novel series is of a low ordered melting type and predominantly nematogenic, without the exhibition of smectogenic character.
- Khunt,Kotadiya,Bhoya
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- The relation between mesomorphism and molecular structure of a novel azoester series involving laterally substituted chloro groups
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A novel azoester homologous series 4-(4'-n-alkoxy benzoyloxy) phenyl azo 2',6'-dichloro benzene is synthesized and studied with a view to understand and establish the effects of molecular structure on liquid crystal behavior of a substance with reference to steric hindrance. The novel homologous series consists of twelve homologues. Mesomorphism commences from the heptyloxy homologue and continues up to the hexadecyloxy homologue as a monotropic nematic without the exhibition of any smectogenic characteristics. Transition temperatures were determined by an optical polarizing microscopy equipped with a heating stage. Transition curves of the phase diagram behave in a normal manner. The isotropic-nematic transition curve shows an odd-even effect in the very short range of temperature. The texture of nematic mesophase is threaded. Analytical and spectral data support the molecular structures of the homologues. Thermal stability is very low and the degree of mesomorphism is poor. Thus novel series is of low melting type and nematogenic only in a monotropic manner. Mesomorphic properties of the present, novel series are compared with structurally similar other known series.
- Maheta,Bhola,Namera,Bhoya
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p. 104 - 113
(2015/03/18)
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- The mesomorphic properties of chalcone dimer derivatives
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A homologous series of symmetrical dimers viz bis (4-n-alkoxy benzoyloxy) -phenyl β-benzoyl-ethylenes was synthesized and studied with a view to understanding the relation between molecular structure and the mesomorphic behavior. Twelve members of the dimeric series were synthesized, and the methoxy to butyloxy homologues are not liquid crystals, but the pentyloxy to hexadecyloxy are liquid crystals. The pentyl to heptyl dimers are only nematogenic, but the higher homologues show smectogenic mesomorphism prior to nematogenic mesophase formation. The phase diagram of phase transition curves behaves in a normal manner except for the smectic to nematic transition curve which behaves in an unexpected manner. The smectic and nematic thermal stabilities are 103°C and 131.7°C, respectively. The smectogenic and nematogenic phase lengths vary between 17.4°C to 28.3°C and 2.1°C to 29.9°C, respectively. The liquid crystal properties of presently investigated novel chalcone dimers are compared with known monomeric chalcones.
- Kotadiya,Bhoya
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p. 116 - 124
(2015/03/18)
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- Effect of a central group on mesomorphism
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A novel homologous series: 4-(4'-n-alkoxy benzoyloxy)-4'-methoxy benzyl benzoates is studied with a view to understanding the effect of a central group on the phenomenon of mesomorphism. The novel homologous series consists of eleven compounds. Mesomorphism commences from the second member of a series. All the mesogenic homologues from ethoxy to hexadecyloxy exhibit nematogenic mesomorphism without the exhibition of smectogenic character. The nematic-isotropic transition curve of the phase diagram behaves in normal manner up to the dodecyloxy homologue and then deviated for the tetradecyloxy and hexadecyloxy homologues. The solid-isotropic or nematic transition curve adopts a normal behavior in a zigzag manner. The nematic-isotropic transition curve shows an odd-even effect and continues up to the octyloxy homologue. Transition and melting temperatures including the textures of mesophases are determined by an optical polarizing microscope, equipped with a heating stage. The textures of the nematic mesophase are threaded or Schlieren in type. Analytical data and spectral data support the molecular structures. The mesomorphic behavior of the present series is compared with structurally similar other known series of differing central group (viz. NN and COCHCH) keeping rest of a molecular part unchanged. The nematic thermal stability of the series is 236.8°C of a high melting type present series whose nematogenic mesophase length varies between 27°C and 98°C. Thus, series is only nematogenic without exhibition of a smectic mesophase.
- Patel, Brijesh H.,Vyas,Doshi
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p. 114 - 122
(2015/03/30)
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- A comparative study of mesomorphism in symmetric and nonsymmetric dimers
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A homologous series consisting of 12 homologue symmetrical dimers, viz., bis(4-n-alkoxy benzoyloxy) 2,2-diphenyl propanes was synthesized, studied, and evaluated to establish the relation between molecular structure and mesomorphic properties on comparative basis with nonsymmectric dimers. The methoxy to pentyloxy homologue dimers, the novel symmetric series, are nonmesogenic. Mesomorphism commences from the hexyloxy homologue as smectic and nematic. The hexyloxy to decyloxy dimers possess smectogenic character with nematogenic character and the dodecyloxy to hexadecyloxy homologue dimers exhibit nematogenic character without the exhibition of smectogenic character. All the mesogenic homologues are enantiotropic mesomorphs. The smectic and nematic thermal stability of series is 129.0°C and 147.7°C, respectively, and mesomorphic phase length varies between 18°C for the hexadecyloxy homologue and 56°C for the heptyloxy homologue.
- Kotadiya,Khunt,Bhoya
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p. 135 - 143
(2015/03/30)
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- Mesomorphism Dependence on Molecular Flexibility by -OCH3 and -H Terminal Units
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A novel ester homologous series: 4-(4′-n-Alkoxy benzoyloxy)-4″-methoxy benzyl cinnamates have been synthesized and studied with a view to understanding and establishing the dependence of liquid crystal behavior on molecular structure. The novel series of eleven homologues is entirely nematogenic without exhibition of any smectogenic character from the very first member of the series. Transition and melting temperatures were determined by an optical polarizing microscopy equipped with a heating stage. Transition curves of a phase diagram show the mesomorphism, which behaves in normal manner. An odd-even effect is exhibited by the nematic-isotropic transition curve. The textures of the nematic mesophase are threaded or schlieren in type. Analytical and spectral data confirm the molecular structures of the novel homologues. Thermal stability for the nematic phase is 211.5°C and the degree of mesomorphism varies from 17°C to 72°C and it is a high melting type series. Mesomorphic properties of the series are compared with structurally similar series.
- Patel, Brijesh H.,Patel,Doshi
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- Study of Novel Symmetrical Liquid Crystalline Ester Dimers
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A novel homologous series of 12 symmetrical dimers, viz. 1,1'-Bis[4-(4'-n-alkoxy benzoyloxy)-3-methyl phenyl] cyclohexanes is reported. Nematogenic mesophase commences from the heptyloxy homologue dimer and continues up to the hexadecyloxy dimer in an enantiotropic manner without the exhibition of any smectogenic behavior. The rest of the dimers from methoxy to hexyloxy are nonmesogenic. The textures of the nematic phase are threaded or Schlieren. The transition temperatures and textures of the nematic phase were determined by an optical polarizing microscope equipped with a heating stage. Curves (solid-isotropic/nematic and N-I) of a phase diagram showing mesomorphism behave in normal manner except for a minor deviation at the dodecyloxy derivative. The analytical and spectral data confirm the molecular structure of dimers. The nematogenic mesophase lengths vary between 3.3°C and 26.6°C. The average thermal stability for nematic is 108.26°C; series is partly nematogenic with middle ordered melting type and low degree of mesomorphism. Liquid crystal properties of novel dimer series are compared with the structurally similar other known series.
- Kotadiya,Bhoya
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- Study of Liquid Crystal Behavior and Dependence on Additional Central Bridge of Ester Homologous Series
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A novel homologous series of esters was synthesized and studied with a view to understanding and establishing the effects of molecular structure on liquid crystal (LC) properties. The series consists of 11 members, and all exhibit enantiotropically the smectogenic mesophase. The nematogenic mesophase is totally absent. The textures of smectic phases are of the type A or C. The Sm-I transition curve of the phase diagram behaves in abnormal manner. The average Sm-I thermal stability is 124.53°C with mesomorphic phase length between 6.5°C and 52.3°C and is of a middle-ordered melting type. LC properties of the novel series are compared with a structurally similar other known series. Analytical and spectral data of the homologous match the molecular structure.
- Marathe, Rajesh B.,Doshi
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- Synthesis and Characterization of a Novel Azoester Homologous Series
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An azoester homologous series of 4-(4'-n-alkoxybenzoyloxy) 3-methylphenyl azo-2''-chloro-3''-methyl benzenes consisting of 12 homologues was synthesized. The methoxy to pentyloxy homologues are nonmesogenic, the hexyloxy to dodecyloxy homologues are monotropic nematic and the tetradecyloxy to hexadecyloxy homologues are enantiotropic nematic. The textures of the nemetic phase are of the threaded or schlieren type. Transition curves showing phase behavior in a phase diagram behave in normal manner, with the exception of the last enantiotropic homologue. An odd-even effect is observed for the nematic-isotropic transition curve. Thermal phase transitions were observed through an optical polarizing microscope equipped with a heating stage. Analytical and spectral data support the molecular structures of the homologue molecules. Smectogenic character is totally absent from all the novel homologues. The average thermal stability for the nematic phase is 121.5 °C. Mesogenic properties of the present novel series are compared with other structurally similar known series.
- Kotadiya,Khunt,Bhoya
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- Synthesis and Mesomorphic Properties of a Novel Ester Homologous Series: 4-(4'- n -Alkoxy Benzoyloxy) Benzyl Cinnamates
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A novel homologous series 4-(4'-n-alkoxy benzoyloxy) benzyl cinnamates was synthesized and studied with a view to understanding and establishing the relationships between mesomorphism and molecular structure. The novel series consists of eleven members with the commencement of mesomorphism from the pentyloxy homologue onwards to the hexadecyl homologue. The remaining homologues are nonmesomorphic. All the mesomorphic homologues exhibit smectogenic mesomorphism in addition to nematogenic mesomorphism for a definite temperature range in an enantiotropic manner, except for the pentyloxy homologue, which exhibits only a nematogenic mesophase in an enantiotropic manner without the formation of a smectic phase. The texture of the nematic mesophase is of the threaded or Schlieren type and the smectic mesophase is of the type A or C texture, as determined by a miscibility method. Transition temperatures were observed through an optical polarizing microscope equipped with a heating stage. The transition curves of a phase diagram predominantly behave in a normal manner, but partly deviated from normal behavior with the exhibition of an odd-even effect. Analytical and spectral data confirms the molecular structures of all homologues. The mesomorphic behavior of the present series is compared with other structurally similar known series. The mesomorphic temperatures vary between 106°C and 180°C. The mesophase length varies between 33°C to 53°C. Thus, the novel series is predominantly nematogenic and partly smectogenic with relatively high transition temperatures and is of a high melting type. The average thermal stabilities for smectic and nematic phases are 144.1°C and 171.4°C, respectively.
- Patel, H. Brijesh,Doshi
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