- Discotic liquid crystals based on Cu(I) complexes with benzoylthiourea derivatives containing a perfluoroalkyl chain
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Mesomorphic three-coordinate copper(I) complexes ([Cu(BTU)2X], where X Cl or Br) based on a new N-benzoylthiourea (BTU) ligand with two decyloxy and one perfluorooctyl groups at its periphery were designed and prepared. The BTU ligand coordinates via the S atom in a neutral monodentate fashion as confirmed by IR and NMR spectroscopy data. The liquid crystalline behavior of these copper(I) complexes was investigated by a combination of polarized optical microscopy (POM), differential scanning calorimetry (DSC), and X-ray diffraction analysis (XRD), while their thermal stability was studied by thermogravimetric analysis (TGA). These new copper(I) complexes have mesomorphic properties and exhibit a hexagonal columnar mesophase over a large temperature range, more than 100°C.
- Ili?, Monica,C?rcu, Viorel
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- Molecular order and mesophase investigation of thiophene-based forked mesogens
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Thiophene-based rodlike molecules constructed from a three phenyl ring core and terminal dialkoxy chains recognized as forked mesogens are synthesized, and their mesophase properties as well as the molecular order are investigated. The synthesized forked
- Reddy, K. Rajasekhar,Lobo, Nitin P.,Narasimhaswamy
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p. 6897 - 6909
(2016/07/26)
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- Liquid-Crystalline Star-Shaped Supergelator Exhibiting Aggregation-Induced Blue Light Emission
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A family of closely related star-shaped stilbene-based molecules containing an amide linkage are synthesized, and their self-assembly in liquid-crystalline and gel states was investigated. The number and position of the peripheral alkyl tails were systematically varied to understand the structure-property relation. Interestingly, one of the molecules with seven peripheral chains was bimesomorphic, exhibiting columnar hexagonal and columnar rectangular phases, whereas the rest of them stabilized the room-temperature columnar hexagonal phase. The self-assembly of these molecules in liquid-crystalline and organogel states is extremely sensitive to the position and number of alkoxy tails in the periphery. Two of the compounds with six and seven peripheral tails exhibited supergelation behavior in long-chain hydrocarbon solvents. One of these compounds with seven alkyl chains was investigated further, and it has shown higher stability and moldability in the gel state. The xerogel of the same compound was characterized with the help of extensive microscopic and X-ray diffraction studies. The nanofibers in the xerogel are found to consist of molecules arranged in a lamellar fashion. Furthermore, this compound shows very weak emission in solution but an aggregation-induced emission property in the gel state. Considering the dearth of solid-state blue-light-emitting organic materials, this molecular design is promising where the self-assembly and emission in the aggregated state can be preserved. The nonsymmetric design lowers the phase-transition temperatures.The presence of an amide bond helps to stabilize columnar packing over a long range because of its polarity and intermolecular hydrogen bonding in addition to promoting organogelation.
- Pathak, Suraj Kumar,Pradhan, Balaram,Gupta, Monika,Pal, Santanu Kumar,Sudhakar, Achalkumar Ammathnadu
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p. 9301 - 9312
(2016/10/06)
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- Self-assembly of hekates-tris(N -salicylideneaniline)s into columnar structures: Synthesis and characterization
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Two series of new, photoluminescent star-shaped discotic liquid crystals, recently termed as "hekates", derived from tris(N-salicylideneaniline) s (TSANs), were synthesized by the facile threefold condensation of 3,4-bis(alkoxy)phenyl 4-aminobenzoates/3,4,5-tris(alkoxy) phenyl 4-aminobenzoates with 1,3,5-triformylphloroglucinol and characterized. These two series of discotics with six and nine peripheral n-alkoxy tails were especially designed and accomplished to understand the relation between mesomorphic/photophysical properties and molecular structure. Proton NMR spectral analysis revealed their existence as an inseparable mixture of two keto-enamine tautomeric forms featuring C3h and Cs rotational symmetries. A systematic study into the thermotropic liquid crystal behavior using polarizing optical microscopy, differential scanning calorimetry, and X-ray scattering confirmed the presence of columnar (Col) phase in vast majority of the TSANs prepared. The two-dimensional (2D) lattices of these fluid columnar phases were found to be characteristic of hexagonal Col (Col h), rectangular Col (Colr), or oblique Col (Col ob) phases depending on the number/length of the peripheral flexible chains. The stabilization of the Colob phase, a less commonly found fluid columnar structure, and the first of its kind in TSAN systems, implies very intensive intermolecular (face-to-face) interactions among the TSAN cores within the column. The photophysical properties were investigated both in solution and the columnar states by UV-vis absorption and photoluminescence; markedly, the solution state emits light in the blue region. The light-emitting ability of the Col phase is particularly significant given the possibility that, in such cores, the protons and electrons interact with each other through the H-bonding environment.
- Achalkumar, Ammathnadu S.,Hiremath, Uma S.,Rao, D. S. Shankar,Prasad, S. Krishna,Yelamaggad, Channabasaveshwar V.
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p. 527 - 544
(2013/03/13)
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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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- A new family of bent-core C2-symmetric liquid crystals
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A series of C2-symmetric compounds with different core sizes and varying lengths and numbers of alkoxy side chains were prepared, and the factors influencing their liquid crystalline mesophase behaviour were investigated. The compounds studied were based on benzophenone, dibenzylidene-acetone, and 1,9-diphenyl-nona-1,3,6,8-tetraen-5-one cores with either 1 or 2 linear alkoxy side chains. The side chains were varied in length from C6H13 to C12H25. The liquid crystalline mesophase behaviour of the compounds was investigated using differential scanning calorimetry, polarizing optical microscopy, and small-angle X-ray scattering (SAXS). It was found that a number of the molecules were able to self-assemble into smectic and nematic liquid crystalline phases.
- Hope-Ross, Kyle A.,Heiney, Paul A.,Kadla, John F.
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p. 639 - 645
(2010/08/21)
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- Propeller-like hydrogen-bonded banana-melamine complexes inducing helical supramolecular organizations
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The results of the study presented here show a new example of the use of liquid crystals and the interactions involved in the mesomorphic state to build up complex molecular organizations. We have pursued a design strategy in which hydrogen bonding allows
- Barbera, Joaquin,Puig, Laura,Romero, Pilar,Serrano, Jose Luis,Sierra, Teresa
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p. 4487 - 4492
(2007/10/03)
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- Lanthanide luminescent mesomorphic complexes with macrocycles derived from diaza-18-crown-6
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Four tetracatenar (L1-L4) and one hexacatenar (L5) ligands, derived from the diaza-18-crown-6 framework, are synthesized and characterized. In these ligands, the amine functions are fitted with benzoyloxybenzyl linker groups, attached either with a carbon
- Suárez, Stéphane,Mamula, Olimpia,Scopelliti, Rosario,Donnio, Bertrand,Guillon, Daniel,Terazzi, Emmanuel,Piguet, Claude,Bünzli, Jean-Claude G.
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p. 1323 - 1334
(2007/10/03)
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- The synthesis and mesomorphism of di-, tetra- and hexa-catenar liquid crystals based on 2,2′-bipyridine
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2,2′-Bipyridines are known to coordinate to a wide variety of metal centres. In this paper, liquid-crystalline two-chained (dicatenar), four-chained (tetracatenar) and six-chained (hexacatenar) bipyridines are synthesised and their mesomorphism is described. For the tetracatenar bipyridines, a full homologous series, from tetramethoxy to tetratetradecyloxy, was synthesised, and the phase diagram showed a classic progression from nematic and smectic C phases at short chain length, through a cubic phase to a columnar phase.
- Rowe, Kathryn E.,Bruce, Duncan W.
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p. 331 - 341
(2007/10/03)
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- Tailoring thermotropic cubic mesophases: Amphiphilic polyhydroxy derivatives
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Novel amphiphilic polyhydroxy compounds [N-(3,4-dialkoxybenzoyl)-1-amino-1-deoxy-D-glucitols (glucamides), N-(3,4-dialkoxybenzoyl)-1-deoxy-1-methylamino-D-glucitols, N-(3,4,5-trialkoxybenzoyl)-1-deoxy-1-methylamino-D-glucitols (N-methylgucamides), 1-benzo
- Borisch, Konstanze,Diele, Siegmar,Goering, Petra,Kresse, Horst,Tschierske, Carsten
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p. 529 - 543
(2007/10/03)
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- Phasmidic phases in macrocyclic liquid crystals
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In this article we describe the synthesis, characterisation and phase behaviour of some phasmidic liquid crystals containing the diaza 18-crown-6 macrocyclic core. Seven compounds were synthesised, five tetracatenar and two hexacatenar. The terminal alkoxy chains were varied in length from ten to eighteen carbon atoms, and the number of phenyl rings in the mesogenic units was set at either two or three. Depending on the nature of the mesogenic moiety, hexagonal columnar phasmidic and smectic phases were found to occur for these systems. The natures and structures of the columnar phases found for these systems are discussed in relation to the conformational structure of the macrocyclic core and to the overall geometry, shape and flexibility of the molecular structures.
- Tuffin, Rachel P.,Toyne, Kenneth J.,Goodby, John W.
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p. 1271 - 1282
(2007/10/03)
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- Influence of lateral alkoxy substitution on mesomorphic properties of copper complexes
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Coordination complexes between copper and some lateral alkoxy chain-substituted N-(4-(4'-alkoxybenzoyloxy)salicylidene)-4-n-butylaniline have been synthesized.The lateral chain was introduced on the outer ring bearing the ester function.In the case of a 3,4-disubstitution, the mesomorphic behavior is related to the number of carbons in the terminal chain.If this is too small, the mesomorphic properties of the complexes disappear.In contrast, copper complexes are liquid crystalline and show more ordered phases by comparison with the free ligand.In case of a 2,4-disubstitution, the phases are nematic and the clearing temperatures are near room temperature, but the observed phases are essentially monotropic for the ligands, as well as for the complexes.Keywords: nematic / copper complex / lateral substitution / Schiff base
- Berdague, Philippe,Perez, Felix,Courtieu, Jacques,Bayle, Jean-Pierre
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p. 335 - 343
(2007/10/02)
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