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Core Units (core + unit)
Selected AbstractsSynthesis and Stereochemical Aspects of 2,6-Disubstituted Perhydroazulenes , Core Units for a New Class of Liquid Crystalline MaterialsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 24 2006Zakir Hussain Abstract A novel approach for the synthesis of cis/trans -fused perhydroazulenes 13,19 is reported. The stereochemistry of the derivatives of carbene addition products 9a,c/20,22, of the 2,6-disubstituted perhydroazulenes 12a,c/23,25, and that of compounds 26,27 has been studied by single-crystal X-ray crystallography. The hydrogenation of the tropylidene to the perhydroazulene skeleton under various conditions is described. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Arborol-Functionalised Tetrathiafulvalene Derivatives: Synthesis and Thin-Film FormationEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 18 2003Thierry Le Gall Abstract The syntheses of a series of novel tetrathiafulvalene derivatives substituted with four side-chains terminating in hydrophilic amidoalcohol (arborol) groups are reported, for example the tetrathiafulvalene derivative 15. Some of these arborol derivatives formed thin films by spin-coating from methanol solution onto solid supports such as glass, ITO-coated glass and gold. The quality of the films improved markedly with an increasing number of alcohol substituents at the periphery of the molecule. Optical absorption spectroscopy showed that oxidative doping of these films could be achieved chemically and electrochemically. The observation of low-energy bands in the UV/Vis absorption spectra (,max = 820 nm tailing to ca. 1300 nm) and the moderate levels of conductivity (,rt , 10,4 S cm,1) in these doped films strongly suggest that a significant degree of supramolecular order is present, with ,-, stacking of the TTF cores. To the best of our knowledge this is the first time that semiconducting behaviour has been achieved in molecular arborol systems that possess an electroactive core unit. This work offers the prospect of using spin-coated films of TTF-arborols as semiconducting charge-transport layers in optoelectronic devices. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Synthesis and Mesomorphic Properties of Some , ,-Alkoxy- , -benzoxypolyfluorotolane CompoundsCHINESE JOURNAL OF CHEMISTRY, Issue 7 2006Chuan Qing Abstract Four homologue series of 4-cyano- and 4-nitro-substituted benzoate-tolanes were synthesized and characterized by IR, NMR, MS spectra and elemental analysis. Their phase transition behaviors were investigated by DSC and polarized optical microscope. The effects on the mesomorphic properties of different positions of the perfluorophenyl in the molecular core unit, the terminal cyano-substituted systems and the terminal nitro-substituted ones were discussed. [source] SMC Proteins at the Crossroads of Diverse Chromosomal ProcessesIUBMB LIFE, Issue 12 2003Rolf Jessberger Abstract How should a protein be designed to serve in processes as diverse as chromosome condensation, sister chromatid cohesion, DNA recombination, gene dosage regulation, and perhaps even gene silencing or transcriptional regulation - which occur in both mitosis and meiosis? Such a protein or protein complex needs to bear DNA interaction domains, it needs the capacity to use energy to move DNA, it needs to enter into highly specific protein interactions, it needs to be large enough to link two DNA molecules, it needs to be of sufficient flexibility to cope with different types of chromatin structure, yet it also needs to be rigid enough to pull, push or enclose DNA. SMC proteins fulfill these requirements and form the core units of high molecular weight complexes that act in all those processes, and are essential for some of them. SMC stands for 'Structural Maintenance of Chromosomes', although SMC proteins are not static scaffold proteins merely providing support for a particular chromosome structure. SMC proteins are rather highly dynamic actors, that generate and modulate chromosome structures, affecting a plethora of biological processes. IUBMB Life, 55: 643-652, 2003 [source] Designing poly(amido amine) dendrimers containing core diversities by click chemistry of the propargyl focal point poly(amido amine) dendronsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 3 2008Jae Wook Lee Abstract General, fast, efficient, and inexpensive methods for the synthesis of poly (amido amine) (PAMAM) dendrimers having core diversities were elaborated. In all syntheses, the major step involved an inexpensive 1,3-dipolar cycloaddition reaction between an alkyne and an azide in the presence of Cu(I) species, which is known as the best example of click chemistry. The propargyl-functionalized PAMAM dendrons are obtained by the divergent approach using propargylamine as an alkyne-focal point. Three core building blocks, 1,3,5-tris(azidomethyl)benzene, N,N,N,,N, -tetra(azidopropylamidoethyl)-1,2-diaminoethane, and 4,4,-(3,5-bis(azidopropyloxy)benzyloxy)bisphenyl, were designed and synthesized to serve as the azide functionalities for dendrimer growth via click reactions with the alkyne-dendrons. These three building blocks were employed together with the propargyl-functionalized PAMAM dendrons in a convergent strategy to synthesize three kinds of PAMAM dendrimers with different core units. This novel and pivotal strategy using an efficient click methodology provides the fast and efficient synthesis of the PAMAM dendrimers with the tailed made core units. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1083,1097, 2008 [source] Preparation and applications of novel cross-linked fluoroalkyl end-capped oligomeric nanocomposites possessing aromatic siloxane segments as core unitsPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 12 2009Yuki Goto Abstract Fluoroalkyl end-capped N,N -dimethylacrylamide oligomer and N -(1,1-dimethyl-3-oxobutyl)acrylamide oligomer were reacted with phenylene- and biphenylene-bridged ethoxysilanes under alkaline conditions to yield cross-linked fluoroalkyl end-capped oligomeric composites possessing aromatic siloxane segments as core units. These isolated fluorinated composite powders were found to be nanometer size-controlled fine particles with a good dispersibility and stability in water and organic solvents. Nitrogen adsorption,desorption isotherms confirmed the presence of micropores in these nanocomposites; the micropore size estimated by the HK method was 0.7,0.8,nm. Interestingly, fluorinated nanocomposites possessing a higher micropore volume ratio were found to exhibit a selective encapsulation ability of fullerene into their composite cores. These fluorinated nanocomposites were also applied to the surface modification of poly(methyl methacrylate) film, resulting in a good oleophobicity imparted by fluorine on the surface. In addition, fluorescence emission was visibly observed only from the modified PMMA film surface treated with fluorinated nanocomposites possessing biphenylene units when irradiated by light. Copyright © 2009 John Wiley & Sons, Ltd. [source] Copper(II) succinate complexes with 1,2-di-4-pyridylethane and 1,3-di-4-pyridylpropaneACTA CRYSTALLOGRAPHICA SECTION C, Issue 11 2009M. J. González Garmendia The compounds poly[di-,4 -succinato-,2 -1,2-di-4-pyridylethane-dicopper(II)], [Cu2(C4H4O4)2(C12H12N2)]n, (I), and poly[di-,4 -succinato-,2 -1,3-di-4-pyridylpropane-dicopper(II)], [Cu2(C4H4O4)2(C13H14N2)]n, (II), exhibit polymeric structures with the dicopper units doubly bridged by bis-bidentate succinate groups and crosslinked by the separator bis(pyridyl) molecules. In (I), the molecule exhibits a centre of inversion located midway between the core Cu-dimer atoms and another that relates half of the bis(pyridyl)ethane ligand to the other half. Compound (II) has a similar molecular packing but with a doubled lattice constant and noncentrosymmetric core units. An antiferromagnetic interaction due to the dinuclear copper units was deduced from magnetic subsceptibility measurements, and spin triplet signals were detected in the electron paramagnetic resonance spectra for both compounds. [source] | |||||||||||||