Liquid Crystals for Charge Transport, Luminescence, and Photonics

O’Neill, Mary; Kelly, Stephen M.

doi:10.1002/adma.200300009

Cited by 620 publications

(361 citation statements)

References 111 publications

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“…Qualitatively similar X-ray patterns were obtained for the two structurally related compounds, namely, HBC-Rf 6,6 (29) and HBC-Rf 4,8 (28), that both exhibit a single mesophase (from 109 and 120°C, respectively). In the small-angle region, four sharp Bragg reflections with the 1, 3, 4, 7 reciprocal spacing ratios were observed, typical for a 2D hexagonal lattice and corresponding to the indexation (hk) ) (10), (11), (20), and (21) (Figures 9A and 9B). The presence of four reflections in the small-angle region of the X-ray pattern indicates that the hexagonal order is well-developed.…”

Section: Liquid Crystalline Propertiesmentioning

confidence: 99%

“…4,5 Additionally, its solubility was improved by the addition of peripheral long aliphatic chains which at the same time bestows the molecule with a ditopic property: These HBC derivatives show a liquid crystalline (LC) state over a wide temperature range depending on the length of the aliphatic chain. 6 Moreover, these HBC derivatives exhibit the highest charge carrier mobility recorded so far for an organic molecule both in the solid and in the liquid crystalline states, 7 paving the way toward their application in the domain of electronic 8 and optoelectronic [9][10][11] devices.…”

Section: Introductionmentioning

confidence: 99%

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Mesomorphic Hexabenzocoronenes Bearing Perfluorinated Chains

et al. 2005

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IntroductionExtended polyaromatic hydrocarbons (PAH) are finding increasing interest among other self-assembled supramolecular systems due to their pronounced tendency for formation of extended π-stacked assemblies. These have many potential properties, such as a high electron density which allows their use in promising applications in molecular electronics. 1 However, the main drawback of these rigid polycondensed molecules resides in the difficulty of their synthesis and their very low solubility which prevents their isolation and manipulation. Recently, Müllen and co-workers 2 succeeded in finding a versatile synthesis of hexa-perihexabenzocoronene (HBC), a polycondensed hexagonal molecule containing 13 benzene rings which shows a very high chemical stability 3 and which self-organizes into columnar stacks, by π-stacking, with an outstanding degree of order in the solid state. 4,5 Additionally, its solubility was improved by the addition of peripheral long aliphatic chains which at the same time bestows the molecule with a ditopic property: These HBC derivatives show a liquid crystalline (LC) state over a wide temperature range depending on the length of the aliphatic chain. 6 Moreover, these HBC derivatives exhibit the highest charge carrier mobility recorded so far for an organic molecule both in the solid and in the liquid crystalline states, 7 paving the way toward their application in the domain of electronic 8 and optoelectronic 9-11 devices.Nevertheless, the lateral interaction between the adjacent HBC stacks caused by the crystalline packing of their aliphatic side chains 12 constitutes a major drawback since it interferes with the formation of very long conducting π-stacks. Additionally, most of the HBCs bearing aliphatic chains are liquid crystalline just above room temperature, which leads to a second disadvantage since it induces a drastic decrease of their charge carrier mobilities, 13 which is reported to be due to "lateral" conduction and as a reason for the perturbation or the deterioration of an ideal liquid crystalline mesophase that dominates the conduction process. 14 * To whom correspondence should be addressed. Tel. (Office): +41 (0) Synthesis and characterization of new hexabenzocoronene (HBC) derivatives bearing perfluoroalkylated chains are described. These disc-shaped polycondensed aromatic hydrocarbons are known to self-assemble by π-stacking into columnar architectures. The peripheral decoration with perfluorinated chains, well-known for their low van der Waals forces, leads as expected to reduced intercolumnar interactions. Powder X-ray diffraction and differential scanning calorimetry of these perfluoroalkylated HBCs proved liquid crystalline (LC) properties whose transition temperatures, mesophase stability, and nature depend on the detailed structure of these side chains, i.e., the ratio between aliphatic and perfluorinated parts. On the other hand, the insertion of a phenyl spacer between the aromatic core and the lateral chains increases the LC transition temperature and, sur...

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Section: Liquid Crystalline Propertiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Mesomorphic Hexabenzocoronenes Bearing Perfluorinated Chains

et al. 2005

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“…Current LC devices such as displays require specific and predictable LC alignment characteristics [1][2][3][4][5] and future LC applications, such as in organic photovoltaics (OPV), will depend on effective alignment of novel materials systems [6]. In the latter case, for example the discotic and polymeric composite systems under development can be difficult to orient in electrically efficient geometries, a problem complicated by the nanoheterogeneity required for efficient PV performance.…”

Section: Introductionmentioning

confidence: 99%

Cooperative liquid-crystal alignment generated by overlaid topography

Maclennan

Clark

2011

Phys. Rev. E

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Nematic and smectic liquid crystals were introduced into micron-scale gaps between plates coated with polymer films nanoimprinted with parallel arrays of rectangular channels. Overlaying of the channels on the two plates close enough at a slight angle produces a mosaic of planar / homeotropic and hybrid alignments, showing that complex liquid crystal orientation patterns can be achieved by combining two simple topographic patterns. These alignment patterns are attributed to spatial variation of surface roughness and 3D topographic structure created by a sufficient proximity of the two patterns.

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“…1,2,3,4,5,6,7,8 These devices require high charge-carrier mobility for operation, and columnar liquid-crystalline materials displaying high charge-carrier mobility along their columnar stacks are particularly attractive for this purpose. 1,9,10,11,12 The transfer efficiency depends on the nature and intensity of the intermolecular interactions that maintain the molecular stacks order over long ranges in the columnar structure. Understanding the dynamics and microscopic phase behavior of columnar discotics at the molecular scale is not simple, but it is fundamental for a rational design of new systems and devices with the desired functionality.…”

Section: Introductionmentioning

confidence: 99%

Isocyano-Triphenylene Complexes of Gold, Copper, Silver, and Platinum. Coordination Features and Mesomorphic Behavior

Chico

Domínguez

Donnio

et al. 2016

Crystal Growth & Design

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Stable organometallic complexes [AuX(CN-TriPh)] [X = Cl, C6F5, C6F4O-C10H21, C6F4O-(R)-2-octyl], [(μ-4,4′-C6F4C6F4){Au(CN-TriPh)}2], [CuCl(CN-TriPh)], trans-[PtI2(CN-TriPh)2], and [Ag(CN-TriPh)2]BF4, bearing the previously unreported triphenylene-isocyanide ligand 1-isocyano-2,3,6,7,10,11-hexadodecyloxytriphenylene (CN-TriPh), have been synthesized. The coordination features of the metal ion determine their thermal behavior. The free isocyanide ligand and all of the monomeric gold derivatives display enantiotropic mesomorphic behavior over a wide range of temperature (from 5 to 220 °C), while the copper complex, with the same stoichiometry but not isostructural with the gold complexes, melts directly to an isotropic liquid. The bis-isocyanide platinum and silver complexes also melt directly to an isotropic liquid at low temperatures. In this case, the two trans coordinated isocyanide ligands, connected by a too short linker, cannot become coplanar, which prevents the formation of a mesogenic structure. On the contrary, in the dinuclear gold complex the two isocyanide trans ligands are, due to the long Au–C6F4–C6F4–Au bridge, sufficiently separated to become coplanar, and this complex gives rise to a mesophase. The structures of the mesophases were determined by small-angle X-ray scattering. All materials prepared show a fluorescent emission centered on the triphenylene core.

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Liquid Crystals for Charge Transport, Luminescence, and Photonics

Cited by 620 publications

References 111 publications

Mesomorphic Hexabenzocoronenes Bearing Perfluorinated Chains

Mesomorphic Hexabenzocoronenes Bearing Perfluorinated Chains

Cooperative liquid-crystal alignment generated by overlaid topography

Isocyano-Triphenylene Complexes of Gold, Copper, Silver, and Platinum. Coordination Features and Mesomorphic Behavior

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