- β-Strand inspired bifacial π-conjugated polymers
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Access to diverse, relatively high molecular weight soluble linear polymers without pendant solubilizing chains is the key to solution state synthesis of structurally diverse nanoribbons of conjugated materials. However, realizing soluble 1D-π-conjugated polymers without pendant solubilizing chains is a daunting task. Herein, inspired from the polypeptide β-strand architecture, we have designed and developed novel bifacial π-conjugated polymers (Mn: ca. 24 kDa) that are soluble (ca. 70 to >250 mM) despite the absence of pendant solubilizing chains. The impact of varying the bifacial monomer height on polymer solubility, optical properties, and interactions with small molecules is reported.
- Chaudhuri, Saikat,Mohanan, Manikandan,Willems, Andreas V.,Bertke, Jeffery A.,Gavvalapalli, Nagarjuna
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- Synthesis of Ultrafine and Highly Dispersed Metal Nanoparticles Confined in a Thioether-Containing Covalent Organic Framework and Their Catalytic Applications
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Covalent organic frameworks (COFs) with well-defined and customizable pore structures are promising templates for the synthesis of nanomaterials with controllable sizes and dispersity. Herein, a thioether-containing COF has been rationally designed and used for the confined growth of ultrafine metal nanoparticles (NPs). Pt or Pd nanoparticles (Pt NPs and Pd NPs) immobilized inside the cavity of the COF material have been successfully prepared at a high loading with a narrow size distribution (1.7 ± 0.2 nm). We found the crystallinity of the COF support and the presence of thioether groups inside the cavities are critical for the size-controlled synthesis of ultrafine NPs. The as-prepared COF-supported ultrafine Pt NPs and Pd NPs show excellent catalytic activity respectively in nitrophenol reduction and Suzuki-Miyaura coupling reaction under mild conditions and low catalyst loading. More importantly, they are highly stable and easily recycled and reused without loss of their catalytic activities. Such COF-supported size-controlled synthesis of nanoparticles will open a new frontier on design and preparation of metal NP@COF composite materials for various potential applications, such as catalysis and development of optical and electronic materials.
- Lu, Shuanglong,Hu, Yiming,Wan, Shun,McCaffrey, Ryan,Jin, Yinghua,Gu, Hongwei,Zhang, Wei
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- Synthesis and optical properties of light-emitting polyfluorene derivatives
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The emitting-polymers, Polyfluorene (PF) and Poly(fluorene- benzothiadiazole-quinoline) [PF-BT-QL], have been synthesized by the Suzuki coupling reactions. The properties of polymers were characterized using UV-Vis spectroscopy, GPC, DSC, TGA, Photoluminescence (PL), Fluoresence (FL), Electroluminescence (EL) spectroscopy. The synthetic polymers were soluble in common organic solvents and easily spin-coated onto the indium-tin oxide (ITO)-coated glass substrates. Light-emitting devices (LEDs) with ITO/PEDOT:PSS/polymer/LiF/Al configuration were fabricated, and the devices using copolymers showed red shift EL spectra relative to that of PF. The turns on voltages of copolymers were lower than that of PF. Copyright Taylor & Francis Group, LLC.
- Aiamsen, Philaiwan,Carroll, David L.,Phanichphant, Sukon
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- Rational design, facile synthesis, and linear/nonlinear optical properties of novel two-photon absorption stilbene derivatives with different configurations
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Four novel two-photon absorption compounds (1MOBI, 2MOHA, 3BrBI, and 4BrHA), which have assembled stilbene π-bridge, different electron acceptors and donors, were synthesized conveniently via the one-step Horner-Wadsworth-Emmons reaction. Their configurations are A-π-D-π-A, D′-π-D-π-D′, A′-π-A-π-A′, and D-π-A-π-D, respectively. Their linear and nonlinear optical properties including linear absorption, one-photon excited fluorescence, two-photon absorption, and two-photon excited fluorescence, were systematically investigated in various solvents. The results demonstrate that the compounds with dihexylamino donors exhibit good optical properties. 2MOHA and 4BrHA exhibit large two-photon absorption cross-sections (2183 and 1737 GM) in DMF, which are larger than those of many known stilbene derivatives. The relationships between the structures and the optical properties were studied aided with the time-dependent density functional theory calculations.
- Cai, Zhi-Bin,Dai, Huan,Li, Sheng-Li,Lou, Qiao-Xian,Tian, Yu-Peng
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- Nonplanar Tub-Shaped Benzocyclooctatetraenes via Halogen-Radical Ring Opening of Dihydrobiphenylenes
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A novel tandem Ru-catalyzed [2+2+2] cycloaddition of arylenynes to dihydrobiphenylenes followed by halogen-radical ring opening has been developed for the construction of tub-shaped halogenated benzocyclooctatetraenes (bCOT's). Cross-couplings and Diels-Alder reactions of the brominated bCOT's allow the formation of the corresponding eight-membered ring-fused PAH's. The halogen-radical ring opening probably occurs via a selective formation of a bis-allyl radical at the 1,3-cyclohexadiene moiety, halogenation at the bridgehead carbon, and finally electrocyclic ring opening.
- Bello-Garciá, Jesús,Padín, Damián,Saá, Carlos,Varela, Jesús A.
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supporting information
p. 5539 - 5544
(2021/07/26)
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- “Golden” Cascade Cyclization to Benzo[c]-Phenanthridines
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Herein, we describe a gold-catalyzed cascade cyclization of Boc-protected benzylamines bearing two tethered alkyne moieties in a domino reaction initiated by a 6-endo-dig cyclization. The reaction was screened intensively, and the scope was explored, resulting in nine new Boc-protected dihydrobenzo[c]phenanthridines with yields of up to 98 %; even a π-extension and two bidirectional approaches were successful. Furthermore, thermal cleavage of the Boc group and subsequent oxidation gave substituted benzo[c]phenanthridines in up to quantitative yields. Two bidirectional approaches under the optimized conditions were successful, and the resulting π-extended molecules were tested as organic semiconductors in organic thin-film transistors.
- Hendrich, Christoph M.,Senn, Sebastian,Haas, Lea,Hoffmann, Marvin T.,Zschieschang, Ute,Greiner, Luca C.,Rominger, Frank,Rudolph, Matthias,Klauk, Hagen,Dreuw, Andreas,Hashmi, A. Stephen K.
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supporting information
p. 14778 - 14784
(2021/09/14)
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- Synthesis and structure of the bimetallic organoantimony catalyst and its application in diastereoselective direct Mannich reaction as facile separation catalytic system
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A bimetallic organoantimony catalyst with four Lewis/Br?nsted acidic/basic sites assembled orderly was successfully synthesized and showed high catalytic efficiency. It has been applied in diastereoselective direct Mannich reaction by adding 0.1 mol% catalyst. This reaction presented unexpected facile separation ability from homogenous solution to heterogeneous solution.
- Tang, Niu,Song, Xingxing,Yang, Tianbao,Qiu, Renhua,Yin, Shuang-Feng
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- Synthesis and photophysics of new pyridyl end-capped 3D-dithia[3.3]paracyclophane-based Janus tectons: Surface-confined self-assembly of their model pedestal on HOPG
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Surface-confined supramolecular self-assembly is currently a promising strategy to create well-organised 2D-networks on conducting surfaces. However, using such substrates tends to quench any electronic properties of the adsorbed molecules. In this context, new pyridyl end-capped 3D-dithia[3.3]paracyclophane-based molecules were designed, along with their model compound (pedestal), with the objective of self-assembling these tectons on any substrate. The synthesis of these new molecules was not straightforward and is consequently described in detail. Once the materials were successfully isolated, their optoelectronic properties were investigated to study potential non-covalent interactions: through pH-dependent absorption and emission measurements, and infra-red spectrometry. We evidenced that both ionic bonding and coordination bonding are compatible with the molecules design. Finally, preliminary scanning tunneling microscopy (STM) studies were performed to study the supramolecular self-assembly properties of the model lower-deck (pedestal) on highly oriented pyrolytic graphite (HOPG): we observed a quasi-square lattice of self-assembled 2D-networks that appear to form independently of the underlying HOPG lattice.
- Attias, A.-J.,Auffray, M.,Charra, F.,Kreher, D.,Mathevet, F.,Sosa Vargas, L.
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p. 7665 - 7674
(2020/06/10)
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- A high efficiency pure organic room temperature phosphorescence polymer PPV derivative for OLED
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For the purpose of improving device efficiency and reducing cost, it is necessary to develop pure organic molecules with room temperature phosphorescence (RTP). A high efficiency pure organic RTP polymer, poly-p-phenylene vinylene (PPV) derivative (Br-PPV-CHO), was designed and synthesized, which possesses a blue emission at 496 nm, an emission lifetime of 14.1 μs, and a photoluminescence quantum yield of 12.2%, and the HOMO and LUMO of ?5.35 eV and ?2.75 eV, respectively, showing a great potential application in the emitting layer of OLED. A device fabricated with the PPV derivative as the emitting material layer shows a max luminance of 194 cd/m2 when the Br-PPV-CHO content was 0.5 wt %, demonstrating the best RTP performance. The good properties of Br-PPV-CHO come from the substituent groups of bromine and aromatic aldehyde, and the molecular structure design strategy in the PPV derivative supplies a useful guidance for the design and syntheses of organic RTP materials.
- He, Ying,Cheng, Nianhe,Xu, Xin,Fu, Jiawei,Wang, Jun-an
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p. 247 - 251
(2018/11/30)
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- An N-heterocyclic carbene-functionalised covalent organic framework with atomically dispersed palladium for coupling reactions under mild conditions
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Covalent organic frameworks (COFs) are a new class of crystalline porous materials that could function as excellent scaffolds for heterogeneous catalysts. Herein, we report a functionalised COF (COF-NHC) using N-heterocyclic carbene (NHC) as a monomer building block via a facile ionothermal strategy. The simple and easily prepared imine-linked COF-NHC possessed two coordination sites (NHC and amine), which could fix the active component (Pd) tightly in COF, leading to atomically dispersed Pd in a heterogeneous catalyst. The as-prepared Pd@COF-NHC showed high stability in the Suzuki-Miyaura coupling reaction of arylboronic acids and aryl halides in aqueous media at room temperature, and could be easily recycled and reused multiple times without the loss of catalytic activity. Moreover, C-C coupling reactions could be accomplished using triarylbismuth reagents in ethanol aqueous solutions with high yields.
- Yang, Junjuan,Wu, Yuanyuan,Wu, Xiaowei,Liu, Wenjing,Wang, Yaofang,Wang, Junwen
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supporting information
p. 5267 - 5273
(2019/10/11)
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- Immobilization of quaternized polymers on bacterial cellulose by different grafting techniques
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Since the discovery of the extraordinary mechanical properties of pristine bacterial cellulose (BC) few decades ago, its potential applications as a textile material and leather-like material have been realized. Immobilization of suitable polymers on the surface of BC can provide two of the most desirable characteristics in the current scenario: improved mechanical strength and variable hydrophobicity. Here, we report the immobilization of suitable polymers on BC surfaces in convenient ways. Different polymers (phosphonium-based or pyridinium-based), different grafting techniques (graft to or direct graft) and different surfaces (bacterial cellulose (BC) or bacterial cellulose-cotton composites (BCC)) were particularly used for comparison. These polymer-functionalized surfaces were characterized by standard instrumentation techniques. Significant improvements in mechanical properties and hydrophobicity were observed for some of the materials after functionalization with the polymers.
- Ramar,Jana, Sourita,Chatterjee, Sandipan,Jaisankar, Sellamuthu N.,Samanta, Debasis
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supporting information
p. 15935 - 15945
(2019/10/28)
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- Coupling N-H Deprotonation, C-H Activation, and Oxidation: Metal-Free C(sp3)-H Aminations with Unprotected Anilines
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An intramolecular oxidative C(sp3)-H amination from unprotected anilines and C(sp3)-H bonds readily occurs under mild conditions using t-BuOK, molecular oxygen and N,N-dimethylformamide (DMF). Success of this process, which requires mildly acidic N-H bonds and an activated C(sp3)-H bond (BDE 85 kcal/mol), stems from synergy between basic, radical, and oxidizing species working together to promote a coordinated sequence of deprotonation: H atom transfer and oxidation that forges a new C-N bond. This process is applicable for the synthesis of a wide variety of N-heterocycles, ranging from small molecules to extended aromatics without the need for transition metals or strong oxidants. Computational results reveal the mechanistic details and energy landscape for the sequence of individual steps that comprise this reaction cascade. The importance of base in this process stems from the much greater acidity of transition state and product for the 2c,3e C-N bond formation relative to the reactant. In this scenario, selective deprotonation provides the driving force for the process.
- Evoniuk, Christopher J.,Gomes, Gabriel Dos Passos,Hill, Sean P.,Fujita, Satoshi,Hanson, Kenneth,Alabugin, Igor V.
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supporting information
p. 16210 - 16221
(2017/11/22)
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- Dimorphism of 1,4-dibromo-2,5-bis(bromomethyl)benzene: Crystallographic and physico-chemical investigations
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Two polymorphic modifications of 1,4-dibromo-2,5-bis(bromomethyl)benzene have been discovered and structurally characterized; their thermodynamic relationships and transformation behaviour have been investigated. Form I crystallizes in the triclinic space group P1, whereas form II crystallizes monoclinic in space group P21/c, both with imposed inversion symmetry of the molecule. Their crystal structures involve layers, in which the molecules are linked by intermolecular Br?Br interactions to form similar systems of linked rings. Initial studies involved batches consisting of pure form I or a mixture of I with traces of II (as obtained by chance from the synthesis), but solvent-mediated conversion experiments in various solvents clearly prove that form II is the thermodynamically stable form at room temperature. Thermomicroscopic and heating-rate-dependent DSC measurements show that the melting point of form I is slightly higher than that of form II and that the higher melting polymorph exhibits the lower heat of fusion. Therefore, form I becomes thermodynamically stable at higher temperatures and both forms are related by enantiotropism. This is also in agreement with the density rule, because the low-temperature form II exhibits the higher density. Isothermal annealing of both modifications at different temperatures reveals a thermodynamic transition temperature of about 135 °C, which is in excellent agreement with that of 137.5 °C calculated from the melting temperatures and the heat of fusion of both forms. The high-temperature form can easily be prepared pure by solidification of the melt, which is in agreement with Ostwald's step rule, because form I crystallizes at a temperature where it is thermodynamically metastable. A qualitative energy/temperature diagram is presented.
- N?ther, Christian,Jess, Inke,Ku?, Piotr,Jones, Peter G.
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p. 3142 - 3149
(2016/06/01)
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- Efficient Synthesis of Bis(dibromomethyl)arenes as Important Precursors of Synthetically Useful Dialdehydes
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This work presents an efficient synthesis of bis(dibromomethyl)benzenes and a bis(dibromomethyl)thiophene as precursors of aromatic dialdehydes by bromination of dimethyl-substituted arenes under various reaction conditions (yields up to 99%). Several new variants of this reaction, including the use of N-bromosuccinimide (NBS) and bromine, and various solvents to replace carbon tetrachloride, benzene and carbon disulfide, were also tested. In the optimised protocols, the inconvenient solvents were replaced by 1,2-dichloroethane (DCE) and/or acetonitrile. In the DCE protocols, we reduced reaction times 24-32-fold, reduced the amount of NBS a fewfold and lowered power consumption relative to the literature protocols. The procedures also allowed elimination of long-lasting incandescent irradiation (100-500 W). The replacement of NBS by bromine led to a further reduction in the amount of brominating agent. The obtained bromo derivatives were efficiently converted into the corresponding dialdehydes (90-96%), which in turn are useful in materials chemistry.
- Bodzioch, Agnieszka,Owsianik, Krzysztof,Skalik, Joanna,Kowalska, Emilia,Stasiak, Anna,Ró?ycka-Soko?owska, Ewa,Marciniak, Bernard,Ba?czewski, Piotr
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p. 3509 - 3514
(2016/10/17)
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- Four- and Sixfold Tandem-Domino Reactions Leading to Dimeric Tetrasubstituted Alkenes Suitable as Molecular Switches
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A highly efficient palladium-catalyzed fourfold tandem-domino reaction consisting of two carbopalladation and two C-H-activation steps was developed for the synthesis of two types of tetrasubstituted alkenes 3 and 6 with intrinsic helical chirality starting from substrates 1 and 4, respectively. A sixfold tandem-domino reaction was also developed by including a Sonogashira reaction. 20 compounds with different substitution patterns were prepared with yields of up to 97%. Structure elucidation by X-ray crystallography confirmed helical chirality of the two alkene moieties. Photophysical investigations of some of the compounds showed pronounced switching properties through light-controlled changes of their stereochemical configuration.
- Tietze, Lutz F.,Waldecker, Bernd,Ganapathy, Dhandapani,Eichhorst, Christoph,Lenzer, Thomas,Oum, Kawon,Reichmann, Sven O.,Stalke, Dietmar
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supporting information
p. 10317 - 10323
(2015/09/01)
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- Water/alcohol soluble electron injection material containing azacrown ether groups: Synthesis, characterization and application to enhancement of electroluminescence
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Using an environmentally stable metal as the cathode in a polymer light-emitting diode (PLED) is an essential requirement for its practical application. We present the preparation of a water/alcohol soluble copoly(p-phenylene) (P1) containing pendant azacrown ether and ethylene glycol ether groups as a highly efficient electron injection layer (EIL) for PLEDs, allowing the use of environmentally stable aluminum as the cathode. Multilayer PLEDs [ITO/PEDOT:PSS/PF-Green-B/EIL/Al] using P1 as EIL exhibit significantly enhanced device performance, particularly in the presence of K 2CO3 or Cs2CO3. The maximum luminous power efficiency and maximum luminance of the device with Cs2CO 3-doped P1 as EIL were enhanced to 9.16 lm W-1 and 17050 cd m-2, respectively, compared with those without EIL (0.16 lm W -1, 890 cd m-2). The turn-on voltage was also significantly reduced from 5.7 V to 3.7 V simultaneously. The performance enhancement has been attributed to improved electron injection which has been confirmed by the rise in open-circuit voltage (Voc) obtained from photovoltaic measurements. The incorporation of such an electron injection layer significantly enhances device performance for PLEDs with an environmentally stable metal as the cathode.
- Wu, Chia-Shing,Lu, Huai-An,Chen, Chiao-Pei,Guo, Tzung-Fang,Chen, Yun
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supporting information
p. 1430 - 1439
(2014/03/21)
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- Copoly(p-phenylene) containing azacrown ether: Synthesis, optical properties, and application for chemical sensor
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Copoly(p-phenylene) (P1) containing pendent azacrown ether and ethylene glycol ether was prepared by the Suzuki coupling reaction and applied for chemical sensor. Poly(p-phenylene) derivative P0 without the azacrown ether groups were also synthesized for comparative study. The photophysical and sensing properties were investigated by absorption and photoluminescence (PL) spectroscopy to elucidate the influence of the azacrown ether groups. The P1 exhibited specific selectivity and high sensitivity toward Zn2+, with the Stern-Volmer coefficient (Ksv) being 3.66 × 106 M-1 at low concentration in mixture solvent of tetrahydrofuran and water (THF/H2O = 9/1, v/v). The P1 maintained high selectivity toward Zn2+ in the presence of fifteen interfering metal cations. This results indicate that copoly(p-phenylene) (P1) is a promising functional material for chemical sensors. Copyright
- Wu, Chia-Shing,Chen, Chiao-Pei,Chen, Yun
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p. 3975 - 3984
(2013/09/02)
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- New side groups-tuned triphenylamine-based chromophores: Synthesis, morphology, photophysical properties and electronic structures
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A new series of crossing symmetric triphenylamine-based chromophores with different side groups were synthesized. Their morphological structure, thermal stabilities and photo-physics were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), differential scanning calorimetry (DSC), thermogravimetric analyzer (TGA), UV-vis spectrophotometer and fluorescent photometer. The results indicated that these compounds emitted green fluorescence with a quantum yield ranging from 0.34 to 0.80 and a lifetime of 0.89 to 1.34 ns. Meanwhile, these compounds with crystal character or amorphous phase exhibited relatively high decomposition and glass transition temperatures. Their electrochemical behaviors and electronic structures were investigated in detail by cyclic voltammetry (CV), and further confirmed by theoretical calculation. The introduced side groups lowered the electron density of the conjugated system, resulting in a significant decrease of LUMO energy level. In a word, it suggested that the optical properties were regulated by the electronics structures with the different effect of the side groups on the LUMO.
- Liu, Pei,Zhang, Peng,Cao, Dongliang,Gan, Lihua,Li, Yuanfang
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p. 151 - 158
(2013/10/01)
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- Aromatizing olefin metathesis by ligand isolation inside a metal- organic framework
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The aromatizing ring-closing metathesis has been shown to take place inside an extended porous framework. Employing a combination of solvent-assisted linker exchange and postsynthesis modification using olefin metathesis, the noninterpenetrated SALEM-14 was formed and converted catalytically into PAH-MOF-1 with polycyclic aromatic hydrocarbon (PAH) pillars. The metal-organic framework in SALEM-14 prevents "intermolecular" olefin metathesis from occurring between the pillars in the presence of the first generation Hoveyda-Grubbs catalyst, while favoring the production of a PAH, which can be released from the framework under acidic conditions in dimethylsulfoxide.
- Vermeulen, Nicolaas A.,Karagiaridi, Olga,Sarjeant, Amy A.,Stern, Charlotte L.,Hupp, Joseph T.,Farha, Omar K.,Stoddart, J. Fraser
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p. 14916 - 14919
(2013/11/06)
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- Synthesis and double doping behavior of a poly(p-phenylenevinylene)s bearing conjugated side chains
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A poly(p-phenylenevinylene) derivative bearing conjugated side chains (polyCPV) was synthesized by Migita-Kosugi-Stille type coupling polycondensation reaction. This polymer contains phenylenevinylene units in both the main chain and the side chains. UV-vis absorption and fluorescence emission spectroscopies revealed a well-developed π-conjugation of the polyCPV. The absorption band of the polymer was extended to long wavelengths. A fluorescent emission maximum of polyCPV is located at considerably longer wavelengths than that of the conjugated side chain monomer. Electron spin resonance measurements of polyCPV confirmed generation of charge species in both the main chain and the side chains via iodine doping.
- Kawashima, Hirotsugu,Kawabata, Kohsuke,Goto, Hiromasa
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experimental part
p. 1530 - 1538
(2012/06/16)
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- Gold(I) styrylbenzene, distyrylbenzene, and distyrylnaphthalene complexes: High emission quantum yields at room temperature
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One gold(I)-substituted styrylbenzene, six digold(I) distyrylbenzenes, one tetragold distyrylbenzene, and four digold distyrylnaphthalene complexes were synthesized using base-promoted auration, alkynylation, triazolate formation, and Horner-Wadsworth-Emmons reactions. The gold(I) fragments are either σ-bonded to the aromatic system, or they are attached through an alkynyl or triazolate spacer. Product formation was monitored using 31P{ 1H} NMR spectroscopy. Systems in which gold(I) binds to the central benzene ring or the terminal phenyl rings were designed. All of these complexes have strong ultraviolet absorptions and emit blue light. The position of the gold(I) attachment influences the luminescence efficiency. Complexes with two gold(I) fragments attached to the ends of the conjugated system have fluorescence quantum yields up to 0.94, when using 7-diethylamino-4- methylcoumarin as the emission standard. Density-functional theory calculations on three high-yielding emitters suggest that luminescence originates from the distyrylbenzene or -naphthalene bridge. Copyright
- Gao, Lei,Niedzwiecki, Daniel S.,Deligonul, Nihal,Zeller, Matthias,Hunter, Allen D.,Gray, Thomas G.
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scheme or table
p. 6316 - 6327
(2012/06/30)
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- Metal ion detection by luminescent 1,3-bis(dimethylaminomethyl) phenyl receptor-modified chromophores and cruciforms
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Chromophores ranging from simple small molecule π-conjugated systems comprised of phenylene ethynylene or fluorenylethynyl units to cross-conjugated Bunz-type cruciforms have been derivatized to include 1,3- bis(dimethylaminomethyl)phenyl moieties. The photophysical responsiveness of these diamino-substituted chromophores to metal ions has been examined. Both emission enhancement (turn-on) and ratiometric fluorescence detection of Cu 2+ and Zn2+ ions have been achieved in THF.
- Mangalum, Anshuman,Gilliard Jr., Robert J.,Hanley, Jessica M.,Parker, Austa Marie,Smith, Rhett C.
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supporting information; experimental part
p. 5620 - 5627
(2011/02/18)
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- Poly(pyridinium phenylene)s: Water-soluble N-type polymers
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(Chemical Equation Presented) Poly(pyridinium phenylene) conjugated polymers are synthesized by a cross-coupling and cyclization sequence. These polyelectrolytes are freely soluble in water and display high degrees of electroactivity. When reduced (n-doped) these materials display in situ conductivities as high as 160 S/cm. The high conductivity is attributed to the planar structure that is enforced by the cyclic structures of the polymer. The electron affinities are compared to PCBM, a C60 based n-type material. We find that these polymers undergo excited state electron transfer reactions with other donor conjugated polymers and hence may find utility in photovoltaic devices.
- Izuhara, Daisuke,Swager, Timothy M.
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supporting information; experimental part
p. 17724 - 17725
(2010/04/01)
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- Synthesis of penta-p-phenylenes with oligo(ethylene glycol) side chains
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We report an efficient synthesis of a series of penta-p-phenylene derivatives with four side chains of various lengths, including deca(ethylene glycol) groups. The key feature of the synthesis is that the side chains are efficiently introduced in the last step, facilitating optimization of the side chains for different applications. Raman spectroscopy study indicates a similarly high rigidity for all these compounds, even those with long oligo(ethylene glycol) side chains. The deca(ethylene glycol)-substituted penta-p-phenylene derivatives are versatile building blocks for construction of nanometric, tripod-shaped adsorbates for biological applications.
- López-Romero, J. Manuel,Rico, Rodrigo,Martínez-Mallorquín, Rocío,Hierrezuelo, Jesús,Guillén, Elena,Cai, Chengzhi,Otero, J. Carlos,López-Tocón, Isabel
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p. 6075 - 6079
(2008/03/12)
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- Polycyclic aromatic hydrocarbons by ring-closing metathesis
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A strategy for the synthesis of polycyclic aromatic hydrocarbons (PAHs) by the ring-closing olefin metathesis (RCM) of pendant olefins on a phenylene backbone has been developed. RCM of 2,4′,6′,2″-tetravinyl-[1, 1′;3′,1″]terphenyl and 2,2′,5′,2″- tetravinyl-[1,1′;4′,1′]terphenyl affords in high yield the isomeric [a,j] and [a,h] dibenzanthracenes, respectively. In contrast with other intramolecular annulation methods, such as Friedel-Crafts acylations, this reaction is completely regioselective. Since RCM is reversible and PAHs are often thermodynamic sinks, this strategy is an effective and general method for the preparation of PAHs. Density functional theory calculations support these results. Carbon disulfide is a suitable solvent for these reactions.
- Bonifacio, Margel C.,Robertson, Charles R.,Jung, Jun-Young,King, Benjamin T.
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p. 8522 - 8526
(2007/10/03)
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- Synthesis of comb-like polyarylenes by oxidattve polymerization of a well-defined polystyrene macromonomer with naphthalene moieties
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Synthesis of a polystyrene (PSt) grafted polyarylene with naphthalene groups in the main chain is described. 1,4-Dibromo-2,5-bis(bromomethyl)benzene was used as initiator in ATRP of styrene using CuBr/2,2′-bipyridine as catalyst and polymeric precursor, that possesses a designed molecular weight with a narrow molecular weight distribution and two bromine atoms directly linked to a central benzene ring, was obtained. The Suzuki coupling between the bromine functionalized PSt and 1-naphihyl boronic acid furnished a macromonomer with naphthyl moieties as oxidable groups. Following chemical oxidative polymerization in the presence of anhydrous FeCl3, a soluble and processable polyarylene with PSt side chains was synthesized. The starting macromonomers as well as the final polyarylenes were analyzed by GPC and spectral methods (1H-NMR, IR and UV-vis). The thermal behaviour of the polymers was studied by differential scanning calorimetry (DSC) and thermogravimetrical analysis (TGA).
- Mercore, Viorela-Mihaela,Cianga, Ioan,Grigoras, Mircea,Yagci, Yusuf
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p. 607 - 616
(2007/10/03)
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- INHIBITORS OF BACE
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The present invention relates to inhibitors of aspartic proteinases, particularly, BACE. The present invention also relates to compositions thereof and methods therewith for inhibiting BACE activity in a mammal, and for treating Alzheimer's Disease and other BACE-mediated diseases.
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- Synthesis, characterization, and fluorescence quenching of novel cationic phenyl-substituted poly(p-phenylenevinylene)s
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Three new phenyl-substituted poly(p-phenylenevinylene) (Ph-PPV) derivatives with amino-functionalized groups were synthesized through either Gilch reaction for poly{2,5-bis[4′-2-(N,N-diethylamino)ethoxyphenyl]-1,4-phenylenevinylene (P1) or Wittig reaction for poly{2,5-bis(4′-decyloxyphenyl)-1,4-phenylenevinylene-alt-2,5-bis[4′ -2-(N,N-diethylamino)ethoxyphenyl]-1,4-phenylenevinylene} (P2) and poly(2,5-bis{4′-2-[2-(2-methoxyethoxy)ethoxy]ethoxyphenyl}-1,4-phenylenevi nylene-alt-2,5-bis[4′-2-(N,N-diethylamino)ethoxyphenyl]-1,4- phenylenevinylene) (P3). Green light-emitting cationic polymers, poly{2,5-bis(4′-decyloxyphenyl)-1,4-phenylenevinylene-alt-2,5-bis[4′ -2-(N,N,N-triethylammonium)ethoxyphenyl]-1,4-phenylenevinylene} dibromide (P2′) and poly(2,5-bis{4′-2-[2-(2-methoxyethoxy)ethoxy]ethoxyphenyl}-1,4-phenylenevi nylene-alt-2,5-bis[4′-2-(N,N,N-triethylammonium)ethoxyphenyl]-1, 4-phenylenevinylene) dibromide (P3′), were prepared from the neutral polymers P2 and P3, respectively. Water solubility was achieved on P3′ through increase of the hydrophilicity of the side chains. The acid-assistant reversible solubility of P1 makes it promising in preparing light-emitting multilayer devices. On the basis of FT-IR and 1H NMR spectra, it was found that P1 is primarily of trans-vinyl while P2 and P3 are of 80% and 81% cis-vinyl, respectively, which depends on the polymerization method employed. The bulky phenyl substituents successfully impeded the interchain interaction which led to quantum efficiency as films comparable to that of solutions. Quaternization also resulted in more twisted conformation of the polymer main chain which was supported by both blue-shifted absorption and reduced quantum efficiency of P2′ and P3′ in solutions and as films than that of the neutral polymers. The fluorescence of P3′ was efficiently quenched by an anionic quencher Fe(CN)64-, Ksv of which is 3.3 × 106 M-1. However, a modified Stern-Volmer plot showed that 9% of the fluophores could not be accessible to the quencher, which may result from the twisted conformation or intermolecular aggregation.
- Fan, Qu-Li,Lu, Su,Lai, Yee-Hing,Hou, Xiao-Yuan,Huang, Wei
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p. 6976 - 6984
(2007/10/03)
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- Layered Compounds. LXII. Triple-layered Paracyclophanes: Syntheses and Spectra
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A series of the title cyclophanes (m,n=2-4) were synthesized by the thermal- and photo-desulfurization methods from dithia intermediates.Their absorption and emission spectra were measured to examine the transannular electronic interaction.The absorbtion spectra of the title compounds and their TCNE complexes gave the same order of the interaction as seen in the case of double-layered system: > > in neutral state and > > in CT state.The emission spectra are discussed in terms of the existence of excited trimer.
- Otsubo, Tetsuo,Kohda, Takashi,Misumi, Soichi
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p. 512 - 517
(2007/10/02)
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