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Rigid Core (rigid + core)
Selected AbstractsMixed f-d Metallomesogens with an Extended Rigid CoreEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 8 2005Koen Binnemans Abstract The liquid-crystalline behaviour of copper(II) and nickel(II) complexes of a mesogenic Schiff-base ligand derived from N,N' -disalicylidene-1,2-phenylenediamine (salophenH2) and of the corresponding trinuclear mixed copper(II)/lanthanum(III) and nickel(II)/lanthanum(III) complexes was investigated. High-temperature X-ray diffraction studies revealed that both the parent transition metal complexes and the mixed f-d complexes exhibit a hexagonal columnar phase (Colh) over an extended temperature range. Complex formation with lanthanum(III) nitrate resulted in an increase of the transition temperatures. The geometrical parameters (lattice parameters and column cross-section) of all the metal complexes are very similar, which indicates that the local organisation in the mesophase is the same despite their structural differences. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Electrophoretic behaviors of human hepatoma HepG2 cellsELECTROPHORESIS, Issue 9 2009Jyh-Ping Hsu Abstract The electrophoretic mobility of HepG2 cells was measured and a charge-regulated model was proposed to simulate the results obtained. Here, a cell was simulated by a rigid core and an ion-penetrable membrane layer containing both acidic and basic functional groups. The influences of the key parameters, including the pH, the ionic strength, the thickness of the membrane layer of a cell, the density and the dissociation constant of the dissociable functional groups in the membrane layer, and the binding constant of divalent cations on the electrophoretic mobility of a cell were investigated. In particular, the role of the buffer used in the experiment was discussed; this effect was neglected in almost all the relevant theoretical analyses in the literature. We showed that the binding ability of divalent cations to the dissociated functional groups in the membrane layer of a cell ranks as Ca2+>Mg2+>hexamethonium. [source] 2,3-Di- n -undecylanthracene and 2,3-Di- n -decyloxyanthracene (DDOA) , on the Connecting Link between the Aromatic Substrate and the Aliphatic Chain in Self-Assembling SystemsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 12 2009Henning Hopf Abstract In contrast to its bis(oxa) analog 1 (DDOA), the hydrocarbon 11 was not found to form organogels with linear alcohols, alkanes, toluene, acetonitrile and other solvents. Whereas the photoreactivity of 1 did not follow the usual behaviour of anthracene derivatives, compound 11, irradiated in cyclohexane, produced the two expected [4+4]cycloadducts 12 and 13 (anti and syn photodimers, respectively). These facts point to the role of the connecting link between the rigid core and the flexible chain for some self-assembled systems.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Formation and applications of stable 10 nm to 500 nm supramolecular porphyrinic materialsISRAEL JOURNAL OF CHEMISTRY, Issue 3 2005Charles Michael Drain Nanoscaled materials of organic dyes are of interest for a variety of potential applications because of the rich photonic properties that this class of molecules can impart. One mode to form such nanoscaled materials is via self-organization and self-assembly, using reasonably well understood methods in supramolecular chemistry. But there are inherent complexities that arise from the use of organic-based supramolecular materials, including stability toward dioxygen, structural stability, and nanoarchitectures that may change with environmental conditions. Porphyrinoids have rich photonic properties yet are remarkably stable, have a rigid core, are readily functionalized, and metalation of the macrocycle can impart a plethora of optical, electronic, and magnetic properties. While there are many <10 nm porphyrinic assemblies, which may or may not self-organize into crystals, there is a paucity of 10,500 nm porphyrinic materials that can be isolated and stored. A variety of strategies towards the latter nanoscopic porphyrinic materials are discussed in terms of design, construction, and nanoarchitecture. The hierarchical structures include colloids, nanorods, nanotubes, nanorings, and nano-crystalline materials. This prolegomenon emphasizes the supramolecular chemistry, structure-stability, and structure-function relationships. The goal herein is to examine general trends and delineate general principles. [source] Fluorene-based liquid crystalline networks with linearly polarized blue emissionJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2007Marta Millaruelo Abstract A series of fluorene-based luminophores containing methacrylic end groups have been prepared and incorporated into uniaxially oriented liquid crystalline films by in situ photopolymerization. Various structural modifications on the 2-(4-cyanophenyl)fluorene core, which include alkyl chains at the 9-position and elongation of the rigid core with one additional phenyl ring, have been investigated to generate emitters with adjusted liquid crystal compatibility, improved luminescence and dichroic properties. Polarized blue-emitting films were produced that had an acceptable photostability, and it was found that the polarization emission was better for samples with low (5%) cross-linker contents. Polarization of the luminescence was favored by the liquid crystalline properties of the luminophore. In addition, the detrimental effect of the alkyl substituent at the fluorene core on the mesomorphism and on the emission polarization can be overcome by lengthening the ,-system. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4804,4817, 2007 [source] Tidal dissipation in rotating fluid bodies: a simplified modelMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2009Gordon I. Ogilvie ABSTRACT We study the tidal forcing, propagation and dissipation of linear inertial waves in a rotating fluid body. The intentionally simplified model involves a perfectly rigid core surrounded by a deep ocean consisting of a homogeneous incompressible fluid. Centrifugal effects are neglected, but the Coriolis force is considered in full, and dissipation occurs through viscous or frictional forces. The dissipation rate exhibits a complicated dependence on the tidal frequency and generally increases with the size of the core. In certain intervals of frequency, efficient dissipation is found to occur even for very small values of the coefficient of viscosity or friction. We discuss the results with reference to wave attractors, critical latitudes and other features of the propagation of inertial waves within the fluid, and comment on their relevance for tidal dissipation in planets and stars. [source] Regions of Tau Implicated in the Paired Helical Fragment Core as Defined by NMRCHEMBIOCHEM, Issue 10 2005Alain Sillen Dr. Abstract We have studied the mature Alzheimer-like fibers of tau by fluorescence and NMR spectroscopy. Assembly of the protein into paired helical filaments after incubation with heparin at 37,°C was verified by electron microscopy and size-exclusion chromatography. NMR spectroscopy on these mature fibers revealed different regions of residual mobility for tau: the N-terminal domain was found to maintain solution-like dynamics and was followed by a large domain of decreasing mobility; finally the core region was distinguished by a solid-like character. Heteronuclear-NOE data indicate that the decreasing mobility is due to both a slowing down of the rapid nanosecond movements and the introduction of slower movements that lead to exchange broadening. Fluorescence spectroscopy confirmed the presence of this rigid core, and some degree of protection from hydrogen exchange for those residues was observed. Hence, our data give a more precise picture of the dynamics of tau when it is integrated into mature filaments and should provide further understanding of the molecular processes that govern aggregation. [source] UV/Vis to NIR Photoconduction in Cyclopalladated ComplexesCHEMISTRY - AN ASIAN JOURNAL, Issue 7 2009Nicolas Godbert Abstract Funky discotics: Photoconductivity is measured in newly synthesized cyclopalladated metallomesogens exhibiting hexagonal columnar mesophases at room temperature. The tuning of the HOMO/LUMO energy levels by modification of the chain/core linkage (ester 1 vs ether 2) makes compound 2 photoconductive across the whole UV/Vis/NIR range. The incorporation of a rigid core, formed by a cyclopalladated azobenzene fragment bonded to an ancillary Schiff base ligand, into molecules with 12 or 11 peripheral alkyl chains has been successfully achieved. These new complexes, 1 and 2, respectively, are columnar liquid crystals between room temperature and about 50,°C. Both cyclometallated and ancillary ligands have been polyalkylated through either aryl ester (electron-withdrawing group) or aryl ether (electron-releasing group) linkages, in order to tune the HOMO/LUMO energy levels. The photoconductive properties of 1 and 2 have been studied as a function of their absorption properties before and after annealing, from the UV/Vis to NIR region. Compared with the reference compounds, tris-alkynyl benzene discotics, these new materials gave similar performances (,/I,8×10,13,S,cm,W,1 with E=10,V,,m,1 at ,=370,nm). Moreover, complex 2 shows a normalized photoconductivity ,/I=8.5×10,13,S,cm,W,1 at ,=760,nm. Organic photoconductors in such a high wavelength spectral range are not common and are usually assembled by mixing dyes with organic semiconductors. [source] Tuning the Polarization Along Linear Polyaromatic Strands for Rationally Inducing Mesomorphism in Lanthanide Nitrate ComplexesCHEMISTRY - A EUROPEAN JOURNAL, Issue 6 2007Emmanuel Terazzi Dr. Abstract The opposite orientation of the ester spacers in the rodlike ligands L,4C12 (benzimidazole-OOC-phenyl) and L,5C12 (benzimidazole-COO-phenyl) drastically changes the electronic structure of the aromatic systems, without affecting their meridional tricoordination to trivalent lanthanides, LnIII, and their thermotropic liquid crystalline (i.e., mesomorphic) behaviors. However, the rich mesomorphism exhibited by the complexes [Ln(L,4C12)(NO3)3] (Ln=La,Lu) vanishes in [Ln(L,5C12)(NO3)3], despite superimposable molecular structures and comparable photophysical properties. Density functional theory (DFT) and time-dependant DFT calculations performed in the gas phase show that the inversion of the ester spacers has considerable effects on the electronic structure and polarization of the aromatic groups along the strands, which control residual intermolecular interactions responsible for the formation of thermotropic liquid-crystalline phases. As a rule of thumb, an alternation of electron-poor and electron-rich aromatic rings favors intermolecular interactions between the rigid cores and consequently mesomorphism, a situation encountered for L,4C12, L,5C12, [Ln(L,4C12)(NO3)3], but not for [Ln(L,5C12)(NO3)3]. The intercalation of an additional electron-rich diphenol ring on going from [Ln(L,5C12)(NO3)3] to [Ln(L,6C12)(NO3)3] restores mesomorphism despite an unfavorable orientation of the ester spacers, in agreement with our simple predictive model. [source] | ||||||||||