- “Effect of the linking unit on the calamitic-shaped liquid crystal: a comparative study of two homologous series of benzoate and cinnamate linked compounds”
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Two homologous series based on three linking groups have been synthesized and well characterized by elemental analyses and spectroscopic techniques such as Fourier transform infrared [FT-IR] and proton magnetic resonance magnetic resonance [1H NMR] spectroscopy. The mesomorphic properties of these compounds were observed by using optical polarized microscopy (POM) and confirmed by differential scanning calorimetry (DSC) analysis. In this present investigation, we have synthesized two homologous series viz. (E)-4-(3-(4-(tetra decanoyloxy) phenyl) acryloyl) phenyl-4-n-alkoxy benzoate (Series-1) and 4-((E)-3-(4-(((E)-3-(4-n-alkoxy phenyl) acryloyl) oxy) phenyl)-3-oxo prop-1-en-1-yl) phenyl tetradecanoate (Series-2). Both of the series are differing with respect to the first linking group. All the homologous in following series displays LC properties on heating as well as cooling condition except first four homologous (C1 to C4) in series-1 and six homologous (C1 to C6) in series-2. To get more insights, the HOMO, LUMO studies are carried out which supports intramolecular charge transfer interactions in this class of mesogens.
- Kashyap, Dinesh,Patel, Sunil,Prajapat, Varsha,Sharma, Vinay,Vasava, Dilip
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- “Synthesis, Mesomorphic and DFT Studies of Chalcone Derived Room Temperature Liquid Crystal with Presence of Lateral Nitro and N, N-Dimethyl Amino Terminal Group”
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In this present article, we wish to report on the liquid-crystalline properties of chalcone-ester based homologous series of compounds having aliphatic chain length in n-alkoxy group (n = 1 to 10, 12, 14, 16, 18). The present series consisted thirteen compounds, in which comp.C1 and C2 shows nonliquid crystalline properties, while comp.C3 to C7 display SmC phase and comp.C8 to C18 exhibits only nematic phase. Textural pattern of presently synthesized compounds are schlieren and threaded type. All this compounds were well characterized by elemental analysis, FT-IR and 1H NMR. Phase transition temperatures of present synthesised compounds were determined by optical polarising microscopy (POM), differential scanning calorimetric (DSC). Detailed XRD investigation endorses the presence of the nematic phase in higher homologues and SmC phase in lower homologues. It is shown that chalcone with ester as linking unit favors a calamitic liquid crystalline behaviour in molecules. To get more insights, the DFT based HOMO, LUMO studies are carried out which supports intramolecular charge transfer interactions in this class of mesogens. Chalconyl ester based compounds C3 to C12 shows antibacterial as well as antifungal activity compared with corresponding standard drugs.
- Shukla, Devendra K.,Sharma, Vinay S.,Prajapat, Varsha,Patel
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- Synthesis, characterization, crystal structure and liquid crystal studies of some symmetric naphthalene derivative molecules
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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.
- Srinivasa,Palakshamurthy,Devarajegowda,Hariprasad
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p. 620 - 626
(2018/09/18)
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- New chalcone based liquid crystals with allylidene amino linking unit: Synthesis and characterization
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In this study, the synthesis, structural characterization and mesomorphic properties of newly thirteen calamitic shaped compounds derived from allylidene amino chalcone and 4-n-alkoxy benzoyloxy benzoic acid. Comp.H1 to H3 exhibited nonliquid crystalline nature, while comp.H4 to comp.H18 displayed enantiotropical smectic C phase. Phase transition temperatures of present synthesised compounds were determined by optical polarising microscopy (POM), differential scanning calorimetric (DSC) and powder X-ray diffraction (PXRD) techniques. Thermal stabilities of smectic to isotropic phase are 150.0 °C and temperature range of mesophase is in decreasing order from comp.H3 to comp.H18 respectively. The presences of SmC phase are the type of broken fan and needle type in present synthesized series. It is also shown that presence of chalcone amino allylidene central linking group favors a calamitic liquid crystalline behaviour in molecules with lower member to higher member aliphatic side chain in alkoxy group (-OR).
- Sharma, Vinay S.,Sharma, Anuj S.,Jadeja, Upendra H.,Suthar, Deepak
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- λ-Shaped mesogens based on chalconyl ester core having variable side chain: Synthesis and characterisation
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In present study, we have synthesized two newly chalconyl-ester core LCs having variable side chain and fixed disubstituted butoxy group at another terminal end. All this compounds were well characterized by elemental analysis, FT-IR, 1H NMR. The mesomorphic properties of these compounds were observed by optical polarized light microscopy (POM) and also confirmed by using differential scanning calorimetry (DSC) and X-ray diffraction pattern (XRD). Detailed XRD investigation endorses the presence of the nematic phase in higher angle region and SmC phase in lower angle region. In addition, it is found that all the prepared materials display enantiotropic LCs phases except first four members in series-1 and first member in series-2. Thermal stability of SmC and nematic phase of series-1 is higher as compare to series-2. To get more insights, the DFT based HOMO, LUMO studies are carried out which supports intramolecular charge transfer interactions and stability in this class of mesogens.
- Sharma, Vinay S.,Suthar, Deepak,Sharma, Anuj S.
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p. 100 - 118
(2019/02/24)
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- Benzimidazole based mesogenic Schiff-bases: Synthesis and characterization
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Two homologous series of mesogenic Schiff-bases, N-4-((alkoxy)-(phenyl-3-hydroxy-4-(4-(5-methylbenzimidazol))-2-alkoxysalicylaldimine)benzoate (7a–d) and N-4′-(5-methyl-benzimidazole)-phenyl-4-alkoxysalicylaldimine (8a–d) incorporating benzimidazole moiety have been prepared and the molecular structures studied by FT-IR, NMR and ESI-MS spectrometry. Mesogenic behaviour was investigated by polarizing optical microscopy (POM), differential scanning calorimetry (DSC) and variable temperature powder X-ray diffraction (PXRD) techniques. Changing the spacer (ester-linked to non-ester linked) of the Schiff-base results in enhancement of thermal stability and phase transition temperature. The members of series-I show monotropic SmA while those of series-II reflect enantiotropic SmA mesomorphism. An electrochemical study of a representative Schiff base in each series (7d and 8c) showed an electrical band gap 1.26?eV and 1.22?eV respectively.
- Dubey, Ragini,Yerrasani, Rajasekhar,Karunakar,Singh, Angad Kumar,Gupta, Rupali,Ganesan, Vellaichamy,Rao
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p. 106 - 114
(2017/05/25)
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- Calamitic-rod-shaped mesogens based on chalcone esters comprising varying alkoxy and lauryl ester chains: Synthesis, mesomorphism and computational study
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In this studywe have synthesized a new class of compounds incorporating of chalconyl-ester and terminally substituted lauryl group. A series of new chalcones with three aromatic rings is synthesized and characterised by elemental analyses and spectroscopic techniques such as Fourier transform infrared [FT-IR] and proton magnetic resonance magnetic resonance [1H NMR] spectroscopy. The mesomorphic properties of these compounds were observed by optical polarized light microscopy (POM) and confirmed by differential scanning calorimetry (DSC). It is found that all the prepared materials display enantiotropic LCs phases except first two homologue in present series. The lowermember comp. (C3 to C6) display only SmC phase while comp. (C7 to C12) shows smectic C as well as nematic phase. The higher member comp. (C14 to C18) display only nematic phase in heating and cooling condition. To get more insights, the HOMO, LUMO studies are carried out which supports intramolecular charge transfer interactions in this class of mesogens. (Figure presented.).
- Sharma, Vinay S.,Patel, Sunil B.,Sharma, Anuj S.,Patel
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- Lanthanide complexes of a mesogenic Schiff's base having 1,3,4-oxadiazole moiety: Synthesis and characterization
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A liquid-crystalline Schiff's base (HL) having 1,3,4-oxadiazole moiety with an octyloxy substituent and a series of lanthanide(III) complexes [Ln(LH)3(NO3)3] (LnIII?=?La, Pr, Nd, Sm, Eu, Tb and Dy; HL?=?N-(4′-(5
- Karunakar,Yerrasani, Rajasekhar,Dubey, Ragini,Singh, Angad Kumar,Rao
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p. 377 - 382
(2016/07/26)
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- Monolayer to Interdigitated Partial Bilayer Smectic C Transition in Thiophene-Based Spacer Mesogens: X-ray Diffraction and 13C Nuclear Magnetic Resonance Studies
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Mesophase organization of molecules built with thiophene at the center and linked via flexible spacers to rigid side arm core units and terminal alkoxy chains has been investigated. Thirty homologues realized by varying the span of the spacers as well as the length of the terminal chains have been studied. In addition to the enantiotropic nematic phase observed for all the mesogens, the increase of the spacer as well as the terminal chain lengths resulted in the smectic C phase. The molecular organization in the smectic phase as investigated by temperature dependent X-ray diffraction measurements revealed an interesting behavior that depended on the length of the spacer vis-a-vis the length of the terminal chain. Thus, a tilted interdigitated partial bilayer organization was observed for molecules with a shorter spacer length, while a tilted monolayer arrangement was observed for those with a longer spacer length. High-resolution solid state 13C NMR studies carried out for representative mesogens indicated a U-shape for all the molecules, indicating that intermolecular interactions and molecular dynamics rather than molecular shape are responsible for the observed behavior. Models for the mesophase organization have been considered and the results understood in terms of segregation of incompatible parts of the mesogens combined with steric frustration leading to the observed lamellar order.
- Kesava Reddy,Varathan,Lobo, Nitin P.,Roy, Arun,Narasimhaswamy,Ramanathan
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p. 10831 - 10842
(2015/10/12)
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- Side-on main-chain liquid crystalline polymers prepared by acyclic diene metathesis polymerization and thiol-ene click step-growth polymerization
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In this manuscript, we design and synthesize a series of X-shaped mesogenic monomers, bearing two terminal-alkene tails. Starting from these X-shaped monomers, acyclic diene metathesis polymerization and thiol-ene polyaddition are applied for the first time to prepare two series of side-on main-chain liquid crystalline polymers (LCPs), respectively. The mesomorphic behaviors and structure-property relationships of these new polymers are studied in detail by a combination of 1H NMR, GPC, TGA, DSC, POM, and XRD experiments. It turns out that the length of alkoxy terminal chains of the embedded mesogens and the length of the spacer connecting two adjacent mesogens on the polymer backbones markedly influence the mesomorphic properties. Furthermore, a side-on main-chain liquid crystalline elastomer fiber is prepared by crosslinking the LCP using a UV-sensitive bifunctional benzophenone crosslinker. In comparison with the pure polymer fiber's monodomain alignment, the crosslinked elastomer fiber however shows nonaligned polydomain structure, probably due to the order competitions between the mixed crosslinkers, mesogens, and polymer backbones. 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 1086-1098 A series of X-shaped mesogenic monomers bearing two polymerizable terminal-alkene tails are designed and synthesized. Starting from these X-shaped monomers, acyclic diene metathesis polymerization (ADMET) and thiol-ene click step-growth polymerization are applied to prepare two series of side-on main-chain liquid crystalline polymers, respectively. Copyright
- Yang, Hong,Lv, You-Jing,Lin, Bao-Ping,Zhang, Xue-Qin,Sun, Ying,Guo, Ling-Xiang
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p. 1086 - 1098
(2014/03/21)
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- High-intensity near-IR fluorescence in semiconducting polymer dots achieved by cascade FRET strategy
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Near-IR (NIR) emitting semiconducting polymer dots (Pdots) with ultrabright fluorescence have been prepared for specific cellular targeting. A series of π-conjugated polymers were synthesized to form water dispersible multicomponent Pdots by an ultrasonic
- Zhang, Xuanjun,Yu, Jiangbo,Rong, Yu,Ye, Fangmao,Chiu, Daniel T.,Uvdal, Kajsa
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p. 2143 - 2151
(2013/06/04)
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- Structure-property correlation of benzoyl thiourea derivatives as organogelators
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A series of N-benzoyl-N′-aryl thiourea derivatives (1-4) can form stable gels from a variety of organic solvents ranging from protic to aprotic or polar to apolar at concentrations below 5 mg/mL. The gelation properties and structures of the resulting gels were investigated by 1H-NMR, FTIR, UV-vis, SEM, and XRD. The gels were anion-responsive and the driving forces for its formation were the hydrogen bonding and van der Waals interaction. The SEM images of the xerogels prepared from the organogels formed in acetonitrile, cyclohexane and acetone showed a network of elongated fibers. The results of XRD suggested that the dry gels had a layer structure.
- Huang, Yao-Dong,Dong, Xue-Lin,Zhang, Li-Li,Chai, Wei,Chang, Ji-Young
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- Room temperature mesogens formed by H-bonded Schiff-bases α,β,γ-triketonates
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Three new series of Schiff bases 1a-c derived from α,β,γ- triketones 2a-c were synthesized and their mesomorphic properties investigated by polarizing optical microscope, differential scanning calorimetry, and powder X-ray diffraction. These Schiff bases
- Kuo, Hsiu-Ming,Cheng, Hsiao-Wen,Sheu, Hwo-Shuenn,Lai, Chung K.
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p. 5945 - 5954
(2013/07/27)
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- Synthesis and characterization of two phenyl ring core-based thiophene mesogens
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Novel thiophene mesogens built with two phenyl ring core and alkoxy terminal chains are synthesized by multistep route. The phenyl ring core is connected to thiophene by ester unit at (a) 2-position and (b) 3-position to yield 2-series of mesogens. The structural characterization of them is accomplished by using spectroscopy tools and the mesophase characteristics are evaluated by HOPM and DSC. The 13C chemical shifts of representative mesogens calculated from DFT by quantum chemical calculations are compared with experimental 13C chemical shifts and further utilized for structural assignment of core unit carbons. A good agreement between calculated and experimental values is noticed. An enantiotropic nematic phase is confirmed for all the mesogens and accordingly threaded nematic texture in HOPM is observed and is supported by DSC transition enthalpy values. The mesophase as well as thermal stabilities of the mesogens are discussed with reference to terminal chain length and position of the linking unit on thiophene.
- Reddy, M. Kesava,Reddy, K. Subramanyam,Prakash,Narasimhaswamy
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- Synthesis of new iridium complexes with substituted 1,3,4-oxadiazole and β-diketones as ligands for OLED application
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New iridium(III) complexes, viz., (OctOXD)2Ir(tta) and (OctOXD)2Ir(tmd) [OctOXD = 2-(4-butyloxyphenyl)-5-phenyl-[1,3,4] oxadiazolato-N4,C2, tta = 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione, tmd = 2,2,6,6-tetramethylheptane-3,5-dio
- Kumar, Amit,Srivastava, Ritu,Kamalasanan, Modeeparampil N.,Singh, Ishwar
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experimental part
p. 937 - 942
(2012/10/08)
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- Mesomorphic behaviour of N-benzoyl-N′-aryl thioureas liquid crystalline compounds
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A series of N-benzoyl-N′-aryl thiourea derivatives bearing alkoxy groups in terminal positions have been prepared and investigated for their potential liquid crystals properties. It was found that only the compounds which have only two alkoxy chains show calamitic mesomorphic behaviour, with nematic, smectic A and C phases being displayed. The type and stability of these mesophases are greatly influenced by the alkyl chain length. Successive introduction of additional alkoxy groups on the benzoyl moiety led to a significant decrease of the clearing points and suppression of the mesogenic character. Using of branched alkyl chain, 2-ethyl-hexyl, instead of normal alkyl group, led to the disappearance of mesogenic behaviour together with the lowering of the clearing temperature. The influence of chain length and number of chains is discussed.
- Ili, Monica,Bucos, Madalina,Dumitracu, Florea,C?rcu, Viorel
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scheme or table
p. 1 - 6
(2011/04/14)
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- Phase characterization and study of molecular order of a three-ring mesogen by 13C NMR in smectic C and nematic phases
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Molecules exhibiting a thermotropic liquid-crystalline property have acquired significant importance due to their sensitivity to external stimuli such as temperature, mechanical forces, and electric and magnetic fields. As a result, several novel mesogens have been synthesized by the introduction of various functional groups in the vicinity of the aromatic core as well as in the side chains and their properties have been studied. In the present study, we report three-ring mesogens with hydroxyl groups at one terminal. These mesogens were synthesized by a multistep route, and structural characterization was accomplished by spectral techniques. The mesophase properties were studied by hot-stage optical polarizing microscopy, differential scanning calorimetry, and small-angle X-ray scattering. An enantiotropic nematic phase was noticed for lower homologues, while an additional smectic C phase was found for higher homologues. Solid-state high-resolution natural abundance 13C NMR studies of a typical mesogen in the solid phase and in the mesophases have been carried out. The 13C NMR spectrum of the mesogen in the smectic C and nematic phases indicated spontaneous alignment of the molecule in the magnetic field. By utilizing the two-dimensional separated local field (SLF) NMR experiment known as SAMPI4, 13C-1H dipolar couplings have been obtained, which were utilized to determine the orientational order parameters of the mesogen. ? 2011 American Chemical Society.
- Kalaivani,Narasimhaswamy,Das, Bibhuti B.,Lobo, Nitin P.,Ramanathan
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scheme or table
p. 11554 - 11565
(2011/12/15)
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- Cyclometalated platinum polymers: Synthesis, photophysical properties, and photovoltaic performance
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The synthesis and characterization of platinum-containing conjugated polymers in which the platinum atom is attached to the conjugated backbone via a CN ligand is presented. The newly designed platinum-containing monomer can be polymerized under both Stil
- Clem, Tabitha A.,Kavulak, David F. J.,Westling, Erik J.,Frechet, Jean M. J.
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experimental part
p. 1977 - 1987
(2011/12/02)
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- Preparation and properties of oxadiazole-containing polyacetylenes as electron transport materials
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A series of functional polyacetylenes (PAs) bearing diphenyl oxadlazole pendant groups (P1-P4) were prepared, and the resultant polymers are completely soluble In common organic solvents, Their structures and properties were characterized and evaluated by
- Wang, Xin,Guan, Shanyi,Xu, Hongyao,Su, Xinyan,Zhu, Xuhui,Li, Chun
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scheme or table
p. 1406 - 1414
(2011/03/19)
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- 1-(4-Alkyloxybenzyl)-3-methyl-1H-imidazol-3-ium organic backbone: A versatile smectogenic moiety
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The merger of ionic liquid and liquid crystal fields, obtained by using the imidazolium ring as a common element, has allowed us to tailor a new set of materials which associate specific functionalities. These functionalities are consequences of the origi
- Dobbs, William,Douce, Laurent,Heinrich, Benoit
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scheme or table
(2010/04/22)
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- NMR-based molecular ruler for determining the depth of intercalants within the lipid bilayer. Part I. Discovering the guidelines
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The development of "molecular rulers" would allow one to quantitatively locate intercalants within the liposomal bilayer. To this end, we have attempted to correlate the 13C NMR chemical shift of a polarizable "reporter" carbon (e.g., carbonyl) of the intercalant-with the ET(30) polarity it experiences, and with its Angstrom distance from the interface. This requires families of molecules with the same two "reporter carbons" separated by a fixed distance, residing at various depths/polarities within the bilayer. The families studied included 4,4-dialkylcyclohexa-2,5-dienones 1, benzenediacetic esters 15, benzenedipropionic esters 17, 4-alkoxybenzaldehydes 19 and methyl 4-alkoxybenzoates 22. These compounds possessed the following characteristics: (1) a planar backbone; (2) polar/hydrophilic "head" groups; (3) modular hydrophobic tails; (4) large changes in the 13C NMR chemical shift (Δδ) of the reporter atoms with solvent polarity. These studies revealed a fifth requirement, namely: (5) the reporter carbons must not be strongly conjugated, lest it reflect the charge build-up at another site within the conjugated system.
- Cohen, Yael,Bodner, Efrat,Richman, Michal,Afri, Michal,Frimer, Aryeh A.
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scheme or table
p. 98 - 113
(2009/12/31)
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- Electron transport agents for organic electronic devices
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Compounds and compositions are provided that can be used as electron transport agents in organic electronic devices such as organic electroluminescent devices. The compounds are non-polymeric and have an aromatic core conjugated to end capping groups. The aromatic core contains a phenylene group arylene or naphthalene group arylene having a pendant heteroaryl group that includes a —C═N— unit.
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- Amphiphilic dendritic dipeptides and their self-assembly into helical pores
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An amphiphilic dendritic dipeptide, comprises a dipeptide(s) comprising one or more of a naturally occurring or synthetic amino acids and a dendron. These are suitable for use in various formulations, films, coatings, membranes and sensors, among other ap
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Page/Page column 42
(2008/06/13)
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- Electroactive polymers
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Electroactive polymeric arylenes and intermediates useful for making such polymers are disclosed. The present invention also provides electroactive compositions comprising the electroactive polymeric arylenes, organic electronic devices which comprise these polymers and compositions, and methods of fabricating these devices.
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Page/Page column 85
(2008/06/13)
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- Synthesis and thermal behavior of new N-heterotolan liquid crystals
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(Chemical Equation Presented) The synthesis of liquid crystal series 9a-d was achieved using the Buchwald protocol and Sonogashira reaction.
- Vasconcelos, Ursula B.,Dalmolin, Emilene,Merlo, Aloir A.
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p. 1027 - 1030
(2007/10/03)
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- ETHYNYL CONTAINING ELECTRON TRANSPORT AGENTS AND THEIR USE IN ORGANIC LUMINESCENT DEVICES
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Compounds of formula (I), compositions, organic electronic devices, and methods for preparing organic electronic devices are described. The compounds of the invention contain at least two carbon-carbon triple bonds and a heteroaromatic ring E having at least one -C=N unit. The compounds can be used as electron transport agents in organic electronic devices such as organic electroluminescent devices.
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- Mesomorphic trigonal bipyramidal iron(0) isocyanide complexes
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The synthesis, characterization and mesomorphic properties of three series of isocyanides and their trigonal bipyramidal iron(0) complexes [Fe(CO)4(CNR)] (R= C6H4O(O)CC6H4C6H4OC(n)H2(n)+1, C6H4C(O)OC6H4C6H4OC(n)H2(n)+1, C6H4C6H4O(O)CC6H4OC(n)H2(n)+1, n = 6, 8, 10, 12) are described. The free isocyanides exhibit nematic and/or smectic A phases for shorter chains (n = 6, 8) and only smectic A phases for longer chains, except the isocyanides CNC6H4O(O)CC6H4C6H4OC(n)H2(n)+1 which melt with extensive decomposition and do not produce mesophases. Their coordination to give the iron complexes [Fe(CO)4(CNR)] produces a slight decrease of their transition temperatures. The iron isocyanide complexes prepared show only a smectic C phase. The relationship between the molecular structure of the complexes and their thermal behaviour is discussed.
- Coco, Silverio,Espinet, Pablo,Marcos, Eva
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p. 1297 - 1302
(2007/10/03)
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- Thermotropic properties of monosubstituted ferrocene derivatives bearing bidentate N-benzoyl-N′-arylthiourea ligands - Novel building blocks for heterometallic liquid crystal systems
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Ferrocene-based derivatives such as 4-{3-[4-(octyloxy)benzoyl]thioureido}phenyl 4-ferrocenylbenzoate and other higher homologues (n = 12,16 and 18; n=length of alkoxy chain) were prepared by reacting 4-alkoxybenzoyl isothiocyanates with the corresponding amines containing the ferrocenyl moiety. Their mesomorphic properties were investigated by means of polarized optical microscopy and differential scanning calorimetry. All the compounds exhibit enantiotropic nematic phases and the nematic range increases with increasing terminal alkyl chain length. On cooling, the nematic phase persists below 0°C in the first three compounds and in the case of n = 18, a phase transformation, possibly to the Sc phase, around 72°C during cooling was observed. In all cases, a glass transition was observed around Tg = 18-35°C, which is remarkable for low molecular mass calamitic metallomesogen systems.
- Seshadri, Tarimala,Haupt, Hans-Juergen
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p. 1345 - 1350
(2007/10/03)
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- Smectic Bimetallomesogens: Synthesis and Mesomorphic Properties in Oxygen-Bridged Dicopper and Divanadyl Complexes
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The synthesis and mesomorphic properties of a homologous series of N-(3-hydroxypropyl)-4-alkoxylsalicylaldimine, N-(3-hydroxypropyl)-4-(4′-alkoxybenzoxy)salicylaldimine, and their dicopper(II) and dioxovanadium(VI) complexes are reported. Copper complexes
- Leu, Yi-Fun,Lai, Chung K.
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- Tilt Angle Variation as a Function of Chain Length and Temperature in the Smectic C Phases of p,Alkoxyphenyl-p,Alkoxybenzoates
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The variation of the tilt angle with temperature in the smectic C phase has generally been shown to be non-existent or very slow for compounds or mixtures with the nematic-smectic C transition, while in the case of systems with the smectic A-smectic C transition, a relation between the steepness of this variation, near the transition, and the width of the smectic A domain has been observed.In this work, the variation of tilt angle in the smectic C phase is described for p-alkoxyphenyl-p-alkoxybenzoate homologous series, for which the evolution of polymorphism can be controlled systematically, by varying stepwise the length of the aliphatic chains, and for which large domains can be obtained for each type of phase sequence, nematic-, smectic A- and isotropic-smectic C.After completing the discussion made previously on the incidence of chain length on polymorphism, we confirm that the variation of tilt angle with temperature is slowest for compounds with intermediate chain lengths corresponding to the largest smectic A temperature range; this variation becomes continuously steeper when the smectic A domain becomes narrow.In addition, we show that the same description can be extended to the other types of phase sequences, by using the hypothesis of a virtual smectic A-smectic C transition above the observed nematic- or isotropic-smectic C transition.In fact, short chain lengths for homologues with a nematic/smectic C transition, or long chain lengths for homologues with an isotropic/smectic C transition, lead to an increase of the tilt angle at the phase transition and to a decrease of the amplitude of its variation with temperature; in our description, this behaviour corresponds to an increase of the temperature range between the real and virtual transitions.As a consequence, the homologues with very short and very long chain lengths show a quasi temperature-independent tilt angle, while the other homologues present a tilt angle variation similar to that observed for compounds exhibiting a smectic C/smectic A transition.This feature indicates that there is no need to distinguish between different types of smectic C phase.
- Heinrich, B.,Guillon, D.
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- Smectic-smectic phase transitions in binary liquid-crystalline mixtures of DB5-T8
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We have used high-resolution x-ray diffraction and ac calorimetry to study the liquid-crystalline smectic-A-smectic-A phase transitions in binary mixtures of polar mesogenic compounds DB5 phenyl ester> and T8 ethenyl> phenyl ester>.A detailed synthesis for each of these compounds is presented.The smectic A1 phase in this system shows two collinear diffuse x-ray maxima at incommensurate wave vectors, indicating a tendency to form the predicted Ai1 phase with two strongly coupled density modulations having incommensurate wavelengths.The Ad peak position, while both temperature and concentration dependent, is remarkably constant along the N-Ad phase boundary.In the vicinity of 16 mol percent T8, both the x-ray and heat-capacity results are reproducibly history dependent.The simultaneous observation of sharp A2 and Ad peaks most likely results from phase coexistence, but a condensed incommensurate Ai2 phase cannot be ruled out.
- Fontes, Ernest,Lee, Wah Keat,Heiney, Paul A.,Nounesis, George,Garland, Carl W.,et al.
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p. 3917 - 3929
(2007/10/02)
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- New potent antagonists of leukotrienes C4 and D4. 1. Synthesis and structure-activity relationships
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(p-Amylcinnamoyl)anthranilic acid (3a) had moderate antagonist activities against LTD4-induced smooth muscle contraction on guinea pig ileum and LTC4-induced bronchoconstriction in anesthetized guinea pigs. Modifications were made in the hydrophobic part (cinnamoyl moiety) and the hydrophilic part (anthranilate moiety) of 3a. A series of 8-(benzoylamino)-2-tetrazol-5-yl-1,4-benzodioxans and 8-(benzoylamino)-2-tetrazol-5-yl-4-oxo-4H-1-benzopyrans were revealed to be potent antagonists of leukotrienes C4 and D4. Among both series, ONO-RS-347 (18k) and ONO-RS411 (19h) were the most potent and orally active antagonists, respectively. Structure-activity relationships are discussed.
- Nakai,Konno,Kosuge,Sakuyama,Toda,Arai,Obata,Katsube,Miyamoto,Okegawa,Kawasaki
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- Alkylphenyl 3-cyano or fluoro-4-alkyloxybenzoates and mesomorphic mixtures thereof
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An organic compound having a high negative dielectric anisotropy is capable, by mixing with a nematic liquid crystal, of improving the dynamic scattering effect of the liquid crystal. The organic compounds have the formula: STR1 in which R is either a flu
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