- A curved graphene nanoribbon with multi-edge structure and high intrinsic charge carrier mobility
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Structurally well-defined graphene nanoribbons (GNRs) have emerged as highly promising materials for the nextgeneration nanoelectronics. The electronic properties of GNRs critically depend on their edge topologies. Here, we demonstrate the efficient synth
- Niu, Wenhui,Ma, Ji,Soltani, Paniz,Zheng, Wenhao,Liu, Fupin,Popov, Alexey A.,Weigand, Jan J.,Komber, Hartmut,Poliani, Emanuele,Casiraghi, Cinzia,Droste, J?rn,Hansen, Michael Ryan,Osella, Silvio,Beljonne, David,Bonn, Mischa,Wang, Hai I.,Feng, Xinliang,Liu, Junzhi,Mai, Yiyong
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p. 18293 - 18298
(2020/11/17)
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- Mixed liquid crystal with huge electrothermal effect being controlled by light and preparation method of mixed liquid crystal
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The invention provides a mixed liquid crystal with a huge electrothermal effect being controlled by light and a preparation method of the mixed liquid crystal. Azobenzene liquid crystal molecules withgood compatibility are added in a liquid crystal mixture, the obtained mixed liquid crystal has large dielectric anisotropy, can orient rapidly under the effect of an electric field, and can recoverto the original orientation behavior under the condition that the electric field is revoked, meanwhile, cis-trans isomerisation can happen on the mixed liquid crystal when the mixed liquid crystal isshined by ultraviolet lights, influences of corresponding properties can be obtained under the effect of the electric field intensity on the electrothermal effect, energy can be saved, and the environment is protected.
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- Pi-Extended Ethynyl 21,23-Dithiaporphyrins: A Synthesis and Comparative Study of Electrochemical, Optical, and Self-Assembling Properties
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21,23-Dithiaporphyrins were synthesized containing pi-extending ethynyl substituents at the meso positions. These porphyrins displayed highly bathochromic and broadened absorbance profiles spanning 400-900 nm with molar absorptivities ranging from 2500 to 300,000 M-1 cm-1. Electrochemically, these ethynyl dithiaporphyrins undergo a single oxidation at 0.44 or 0.57 V and reduction at -1.17 or -1.08 V versus a ferrocene/ferrocenium internal standard depending on the type of functionalization appended to the ethynyl group. DFT calculations predict that the delocalization of the frontier molecular orbitals should expand onto the meso positions of the ethynyl 21,23-dithiaporphyrins; shrinking the HOMO-LUMO energy gap by destabilizing the HOMO energy. Indeed, the DFT results agree with our optical and electrochemical assessments. Finally, differential scanning calorimetry combined with cross-polarized optical microscopy and powder X-ray diffraction was used to assess the ability of these porphyrins for long-range order. For the ethynylphenyl alkoxy 21,23-dithiaporphyin, birefringent, soft-crystalline-like domains were observed by polarized microscopy, which are marginally sustained by a low-level of crystallinity detected in the XRD, suggesting that long-range ordering is possible. Overall, ethynyl 21,23-dithiaporphyrins are able to harvest much lower energy light and possess lower oxidation and reduction potentials compared to their pyrrolic analogues, which are desirable properties for applications in organic electronics.
- Bromby, Ashley D.,Keller, Samantha N.,Bozek, Kevin J. A.,Williams, Vance E.,Sutherland, Todd C.
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p. 9401 - 9409
(2015/10/12)
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- Fused π-extended discotic triangular porphyrinoids
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A novel fused two-dimensionally π-expanded triangular porphyrinoid has been designed. The synthesis is based on facile hexaazatrinaphthalene chemistry in combination with well-established condensation procedures to simultaneously close three porphyrinic cavities. A series of different functionalized π-expanded triangular derivatives were synthesized and their optical and electrochemical properties, as well as their supramolecular organization investigated. Low lying HOMOLUMO energy gaps between 1.111.32 eV were found for the highly π-conjugated planar triangular hexaazatrinaphthalene derivatives which organize into discotic liquid crystalline columnar stacks. Thereby, derivatives with alkoxy substituents reveal significantly higher order due to their improved flexibility in comparison to their alkyl counterparts.
- Arnold, Lena,Puniredd, Sreenivasa Reddy,Von Malotki, Christian,Pisula, Wojciech,Koshino, Nobuyoshi,Higashimura, Hideyuki,Baumgarten, Martin,Wagner, Manfred,Müllen, Klaus
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experimental part
p. 564 - 575
(2012/09/21)
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- Tuning the optical and electronic properties of 4,8-disubstituted benzobisoxazoles via alkyne substitution
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In an effort to design new electron-deficient building blocks for the synthesis of conjugated materials, a series of new trans-benzobisoxazoles bearing halogen or alkynyl substituents at the 4,8-positions was synthesized. Additionally, the impact of these modifications on the optical and electronic properties was investigated. Theoretical calculations predicted that the incorporation of various alkynes can be used to tune the energy levels and band gaps of these small molecules. The targeted 4,8-disubstituted benzobisoxazoles were easily prepared in good yields using a two-step reaction sequence: Lewis acid catalyzed orthoester cyclization followed by Sonogashira cross-coupling. The experimentally determined HOMO values for these 4,8-disubstituted benzobisoxazoles ranged from -4.97 to -6.20 eV and showed reasonable correlation to the theoretically predicted values, with a percent deviation that ranged from 2.4-12.8%. However, the deviation between actual and predicted HOMO values was reduced to less than 3.5% when the theoretical values were extrapolated to the long-chain limit and compared to copolymers containing the 4,8-disubstituted benzobisoxazoles. Collectively, these results indicate that these 4,8-disubstituted trans-benzobisoxazoles can be used for the synthesis of new conjugated materials with electronic properties that are variable and predictable.
- Tlach, Brian C.,Tomlinson, Aimee L.,Bhuwalka, Achala,Jeffries-El, Malika
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p. 8670 - 8681
(2011/12/22)
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- A self assembled molecular zipper based on a perfluorophenyl-phenyl diacetylene motif
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The synthesis and characterization of a molecular rod consisting of a pentafluorophenyl and a para-dodecylphenyl subunit linked by a diacetylene and its large area self assembly into perfect parallel lines consisting of interlocked molecular rods are reported and discussed. The Royal Society of Chemistry 2006.
- Shu, Lijin,Mu, Zhongcheng,Fuchs, Harald,Chi, Lifeng,Mayor, Marcel
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p. 1862 - 1863
(2008/03/14)
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- Room-temperature discotic nematic liquid crystals
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The use of discotic nematic liquid crystals instead of calamitic nematic liquid crystals to improve the viewing angle of a liquid crystal display device has recently been reported. Compared to the large number of calamitic molecules showing nematic phase at room temperature, the number of disk-shaped molecules showing subambient discotic nematic phase ND are rare. In this paper we present the design, synthesis, mesomorphic behaviour and structureproperty relationship of discotic nematic liquid crystals based on benzene multiyne core.
- Kumar, Sandeep,Varshney, Sanjay Kumar,Chauhan, Diwakar
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p. 241 - 250
(2007/10/03)
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- Synthesis and self-assembly of functionalized hexa-peri-hexabenzocoronenes
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Monolayers of hexa-alkyl substituted derivatives of hexa-peri-hexabenzocoronene (HBC) 1b have previously been investigated by scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS). It is expected that different functional groups (electron donating or withdrawing) connected to the aromatic core will influence the packing pattern and possibly the current-voltage characteristics as well. In order to provide suitable model systems, a new synthetic approach to synthesize functionalized HBC derivatives has been developed. This was accomplished by [4+2]-cycloaddition of suitably bromo-substituted diphenyl-acetylenes and 2,3,4,5-tetraarylcyclo-penta-2,4-dien-1-ones followed by an oxidative cyclodehydrogenation with iron(III) chloride/nitromethane. Using this strategy three different substitution patterns were synthesized: 2-bromo-5,8, 11,14,17-pentadodecylhexa-peri-hexabenzocoronene (2a), 2,5-dibromo-8,11,14,17-pentadodecylhexa-peri-hexabenzocoronene (2b), and 2,11-dibromo-5,8,14,17-pentadodecylhexa-peri-hexabenzocoronene (2c). These bromo-substituted HBC derivatives were subjected to palladium catalyzed coupling reactions to give donor (alkoxy, amino) as well as acceptor (ester, cyano) substituted derivatives. The self-assembly of these new HBC derivatives was studied in the bulk as well as at an interface. DSC, optical microscopy, and X-ray diffraction revealed the existence of columnar mesophases. The bulk structure in the mesophase is largely insensitive to changes of the substitution pattern; however, in situ scanning tunneling microscopy at the solid-fluid interface between an organic solution of the HBC derivative and highly oriented pyrolytic graphite reveals different packing patterns of the first adsorbed monolayer.
- Ito, Shunji,Wehmeier, Mike,Diedrich Brand,Kuebel, Christian,Epsch, Rebekka,Rabe, Juergen P.,Muellen, Klaus
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p. 4327 - 4342
(2007/10/03)
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- Diodenartige Strom-Spannungs-Kennlinie durch ein einzelnes Molekuel - Rasttertunnel - spektroskopie mit submolekularer Aufloesung an einem alkylierten, peri-kondensierten Hexabenzocoronen
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Stichworte: Arene, Einzelmolekuelspektroskopie, Rastertunnel-mikroskopie
- Stabel, Andreas,Herwig, Peter,Muellen, Klaus,Rabe, Juergen P.
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p. 1768 - 1770
(2007/10/02)
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