Twists in mesomorphic columnar supramolecular assemblies

Vera, Francisco; Serrano, José Luís; Sierra, Teresa

doi:10.1039/b800408k

Cited by 130 publications

(86 citation statements)

References 51 publications

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“…It is known that molecular chirality (stereocentres) can impose a preferential handedness of the helical arrangement of mesogens in columnar phases. [26] In this case, stacking of blocks for rendering the column seems to be governed by stereocentres giving rise to a chiral helix, which is responsible for the negative exciton couplet detected with a crossover located at around 290 nm and the positive Cotton effect detected at 275 nm due to mesogenic chromophores affected by helical ordering. The X-ray patterns recorded on cph-A3 are very different from those described for cph-A1 and cph-A2.…”

Section: Wwwchemeurjorgmentioning

confidence: 97%

Supermolecular Liquid Crystals with a Six‐Armed Cyclotriphosphazene Core: From Columnar to Cubic Phases

Jiménez

Laguna

Molter

et al. 2010

Chemistry A European J

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New liquid crystals having a non-conventional structure have been synthesised from a six-armed cyclotriphosphazene core, [N(3) P(3) (OC(6) H(4) OH-4)(6) ], which was condensed with polycatenar acids. Reactions were monitored by (31) P{(1) H} and (1) H NMR spectroscopy and the chemical structure of the resulting materials was confirmed by different spectroscopic techniques and mass spectrometry (MALDI-TOF). Results were in accordance with monodisperse, fully functionalised cyclotriphosphazenes. Thermal and mesomorphic properties were studied by optical microscopy, differential scanning calorimetry and X-ray diffraction. All of the synthesised phosphazenes, substituted with benzyl ether chains, show a high thermal stability and exhibit mesomorphic properties, which depend on the number and type of alkyl terminal chains located at the periphery of the mesogens. Mesomorphic properties range from Col(h) for cph-A1 and cph-A2 to a cubic phase detected for cph-A3, which has the larger number of alkyl chains. Furthermore, helical order was detected on X-ray data of cph-A2, which has chiral branched chains. Circular dichroism spectra of annealed films at mesophase temperature show a signal attributed to the chiral helical arrangement of the mesogenic chromophores.

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Section: Wwwchemeurjorgmentioning

confidence: 97%

Supermolecular Liquid Crystals with a Six‐Armed Cyclotriphosphazene Core: From Columnar to Cubic Phases

Jiménez

Laguna

Molter

et al. 2010

Chemistry A European J

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“…triphenylenes [8] and hexabenzocoronenes, [7,9] the close molecular packing in columnar ordered and plastic phases results from a spontaneous helical twist in the columns (spontaneous symmetry breaking). [10] Overall, for nonchiral molecules, helical columns with opposite handiness are formed in equal amounts giving rise to a racemic bulk material. For materials that already have twisted columns formed by achiral molecules, a uniform sense of handiness of the helical twist is achieved by using peripheral alkyl chains containing stereogenic centres.…”

Section: Introductionmentioning

confidence: 99%

Chiral discotic derivatives of 1,3,5-triphenyl-6-oxoverdazyl radical

et al. 2014

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Two derivatives of 1,3,5-aryl-6-oxoverdazyl containing two 3,4,5-trioctyloxyphenyl and one 3,4,5-tri((S)-3,7-dimethyloctyloxy)phenyl group in position C(3) (1b) or N(1) (1c) were investigated by thermal, X-ray diffraction and magnetic methods. The results were compared to those obtained for achiral derivative 1a containing three 3,4,5-trioctyloxyphenyl groups. All three compounds exhibit an ordered columnar hexagonal phase, Col h(o) , and for chiral derivatives, 1b and 1c, a superstructure with doubled periodicity was found. The introduction of the three chiral alkoxy substituents in 1a lowered the mesophase stability by about 50 K and induced a Col h phase in 1c. Thermochromic analysis showed a hypsochromic shift upon formation of the Col h(o) phase similar for all three derivatives 1 (~0.3 eV), which coincides with a 5% drop in effective magnetic moment, μ eff , for 1c. Analysis of magnetisation data in a range of 2-370 K at 200 Oe revealed weak antiferromagnetic interactions (θ = -4 K) in the Col h(o) phase.

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“…review ref. 38. But these examples have all involved "classical" column-forming mesogens, typically disc-like or wedge-like with spread-out flexible tails forming a shield around each column.…”

mentioning

confidence: 99%

Helically Twisted Chiral Arrays of Gold Nanoparticles Coated with a Cholesterol Mesogen

et al. 2015

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Gold nanoparticles have been prepared, surface-functionalized with a 1:1 molar mixture of a hexylthiol ligand and a chiral mesogenic ligand consisting of a cholesterylbenzoate attached via an undecylthiol spacer. Grazing incidence Xray diffraction showed that, upon annealing, a columnar liquid crystal (LC) structure develops, with the nanoparticles forming strings on a regular oblique 2d lattice. Synchrotron radiation circular dichroism is substantially enhanced upon the isotropic-LC transition. In the proposed structural model, layers of gold columns rotate by a small angle relative to their neighbors, the columns winding around a helical axis. The work demonstrates that it is possible to obtain chiral LC superstructures from nanoparticles coated with chiral mesogen without the addition of a separate liquid crystal or chiral dopants. The results provide direction in the development of plasmonic metamaterials interacting selectively with circularly polarized light.

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Twists in mesomorphic columnar supramolecular assemblies

Cited by 130 publications

References 51 publications

Supermolecular Liquid Crystals with a Six‐Armed Cyclotriphosphazene Core: From Columnar to Cubic Phases

Supermolecular Liquid Crystals with a Six‐Armed Cyclotriphosphazene Core: From Columnar to Cubic Phases

Chiral discotic derivatives of 1,3,5-triphenyl-6-oxoverdazyl radical

Helically Twisted Chiral Arrays of Gold Nanoparticles Coated with a Cholesterol Mesogen

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