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Aromatic Backbone (aromatic + backbone)
Selected AbstractsThiophene,Benzothiadiazole Co-Oligomers: Synthesis, Optoelectronic Properties, Electrical Characterization, and Thin-Film PatterningADVANCED FUNCTIONAL MATERIALS, Issue 3 2010Manuela Melucci Abstract Newly synthesized thiophene (T) and benzothiadiazole (B) co-oligomers of different size, alternation motifs, and alkyl substitution types are reported. Combined spectroscopic data, electrochemical analysis, and theoretical calculations show that the insertion of a single electron-deficient B unit into the aromatic backbone strongly affects the LUMO energy level. The insertion of additional B units has only a minor effect on the electronic properties. Cast films of oligomers with two alternated B rings (B,T,B inner core) display crystalline order. Bottom-contact FETs based on films cast on bare SiO2 show hole-charge mobilities of 1,×,10,3,5,×,10,3,cm2 V,1s,1 and Ion/Ioff ratios of 105,106. Solution-cast films of cyclohexyl-substituted compounds are amorphous and do not show FET behavior. However, the lack of order observed in these films can be overcome by nanorubbing and unconventional wet lithography, which allow for fine control of structural order in thin deposits. [source] Poly(9,9-dioctylfluorene)-Based Conjugated Polyelectrolyte: Extended ,-Electron Conjugation Induced by Complexation with a Surfactant ZwitterionADVANCED MATERIALS, Issue 18 2010Giuseppina Pace We report on a conjugated polyelectrolyte (CPE) based on fluorene repeat units, which forms a supramolecular complex with a zwitterion surfactant. The complex self-assembles into multilamellar structures on solid substrates. The luminescence efficiency, low in the uncomplexed polymer, is strongly increased after complexation. This originates from the phase segregation between the aromatic backbone and ionic sides, reducing conformational defects and ionic dipole-induced quenching. [source] Efficient Heterogeneous Dual Catalyst Systems for Alkane MetathesisADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1 2010Zheng Huang Abstract A fully heterogeneous and highly efficient dual catalyst system for alkane metathesis (AM) has been developed. The system is comprised of an alumina-supported iridium pincer catalyst for alkane dehydrogenation/olefin hydrogenation and a second heterogeneous olefin metathesis catalyst. The iridium catalysts bear basic functional groups on the aromatic backbone of the pincer ligand and are strongly adsorbed on Lewis acid sites on alumina. The heterogeneous systems exhibit higher lifetimes and productivities relative to the corresponding homogeneous systems as catalyst/catalyst interactions and bimolecular decomposition reactions are inhibited. Additionally, using a "two-pot" device, the supported Ir catalysts and metathesis catalysts can be physically separated and run at different temperatures. This system with isolated catalysts shows very high turnover numbers and is selective for the formation of high molecular weight alkanes. [source] Poly[bis(,-benzene-1,4-dicarboxylato)bis[,-6-(4-pyridyl)-5H -imidazolo[4,5- f][1,10]phenanthroline]dilead(II)]: an interpenetrating ,-Po netACTA CRYSTALLOGRAPHICA SECTION C, Issue 9 2010Zhan-Lin Xu The asymmetric unit of the title compound, [Pb2(C8H4O4)2(C18H11N5)2]n, contains two PbII atoms, two benzene-1,4-dicarboxylate (1,4-bdc) dianions and two 6-(4-pyridyl)-5H -imidazolo[4,5- f][1,10]phenanthroline (L) ligands. Each PbII atom is eight-coordinated by three N atoms from two different L ligands and five carboxylate O atoms from three different 1,4-bdc dianions. The two 1,4-bdc dianions (1,4-bdc1 and 1,4-bdc2) show different coordination modes. Each 1,4-bdc1 coordinates to two PbII atoms in a chelating bis-bidentate mode. Each carboxylate group of the 1,4-bdc2 anion connects two PbII atoms in a chelating,bridging tridentate mode to form a dinuclear unit. Neighbouring dinuclear units are connected together by the aromatic backbone of the 1,4-bdc dianions and the L ligands into a three-dimensional six-connected ,-polonium framework. The most striking feature is that two identical three-dimensional single ,-polonium nets are interlocked with each other, thus leading directly to the formation of a twofold interpenetrated three-dimensional ,-polonium architecture. The framework is held together in part by strong N,H...O hydrogen bonds between the imidazole NH groups of the L ligands and the carboxylate O atoms of 1,4-bdc dianions within different ,-polonium nets. [source] Solubility-Induced Ordered Polythiophene Precursors for High-Performance Organic Thin-Film TransistorsADVANCED FUNCTIONAL MATERIALS, Issue 8 2009Yeong Don Park Abstract With the aim of enhancing the field-effect mobility of self-assembled regioregular poly(3-hexylthiophene), P3HT, by promoting two-dimensional molecular ordering, the organization of the P3HT in precursor solutions is transformed from random-coil conformation to ordered aggregates by adding small amounts of the non-solvent acetonitrile to the solutions prior to film formation. The ordering of the precursor in the solutions significantly increases the crystallinity of the P3HT thin films. It is found that with the appropriate acetonitrile concentration in the precursor solution, the resulting P3HT nanocrystals adopt a highly ordered molecular structure with a field-effect mobility dramatically improved by a factor of approximately 20 depending on the P3HT concentration. This improvement is due to the change in the P3HT organization in the precursor solution from random-coil conformation to an ordered aggregate structure as a result of the addition of acetonitrile. In the good solvent chloroform, the P3HT molecules are molecularly dissolved and adopt a random-coil conformation, whereas upon the addition of acetonitrile, which is a non-solvent for aromatic backbones and alkyl side chains, 1D or 2D aggregation of the P3HT molecules occurs depending on the P3HT concentration. This state minimizes the unfavorable interactions between the poorly soluble P3HT and the acetonitrile solvent, and maximizes the favorable ,,, stacking interactions in the precursor solution, which improves the molecular ordering of the resulting P3HT thin film and enhances the field-effect mobility without post-treatment. [source] | |||||||||||||