- Dependence of single-molecule conductance on molecule junction symmetry
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The symmetry of a molecule junction has been shown to play a significant role in determining the conductance of the molecule, but the details of how conductance changes with symmetry have heretofore been unknown. Herein, we investigate a naphthalenedithiol single-molecule system in which sulfur atoms from the molecule are anchored to two facing gold electrodes. In the studied system, the highest single-molecule conductance, for a molecule junction of 1,4-symmetry, is 110 times larger than the lowest single-molecule conductance, for a molecule junction of 2,7-symmetry. We demonstrate clearly that the measured dependence of molecule junction symmetry for single-molecule junctions agrees with theoretical predictions.
- Taniguchi, Masateru,Tsutsui, Makusu,Mogi, Ryoji,Sugawara, Tadashi,Tsuji, Yuta,Yoshizawa, Kazunari,Kawai, Tomoji
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Read Online
- A synthetic receptor for nicotine from a dynamic combinatorial library
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Designing synthetic receptors that bind biologically relevant guests in an aqueous solution remains a considerable challenge. We now report a new synthetic receptor for nicotine, selected from a dynamic combinatorial library, that binds this guest in water at neutral pH through a combination of hydrophobic and π-π interactions.
- Hamieh, Saleh,Ludlow, R. Frederick,Perraud, Olivier,West, Kevin R.,Mattia, Elio,Otto, Sijbren
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supporting information
p. 5404 - 5407
(2013/01/15)
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- Molecular tunnel junctions based on π-conjugated oligoacene thiols and dithiols between Ag, Au, and Pt contacts: Effect of surface linking group and metal work function
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The tunneling resistance and electronic structure of metal-molecule-metal junctions based on oligoacene (benzene, naphthalene, anthracene, and tetracene) thiol and dithiol molecules were measured and correlated using conducting probe atomic force microscopy (CP-AFM) in conjunction with ultraviolet photoelectron spectroscopy (UPS). Nanoscopic tunnel junctions (～10 nm2) were formed by contacting oligoacene self-assembled monolayers (SAMs) on flat Ag, Au, or Pt substrates with metalized AFM tips (Ag, Au, or Pt). The low bias (0 exp(βs), where R0 is the contact resistance and β is the tunneling attenuation factor. The R0 values for oligoacene dithiols were 2 orders of magnitude less than those of oligoacene thiols. Likewise, the β value was 0.5 per ring (0.2 A-1) for the dithiol series and 1.0 per ring (0.5 A-1) for the monothiol series, demonstrating that β is not simply a characteristic of the molecular backbone but is strongly affected by the number of chemical (metal-S) contacts. R0 decreased strongly as the contact work function (Φ) increased for both monothiol and dithiol junctions, whereas β was independent of Φ within error. This divergent behavior was explained in terms of the metal-S bond dipoles and the electronic structure of the junction; namely, β is independent of contact type because of weak Fermi level pinning (UPS revealed EF - EHOMO varied only weakly with Φ), but R0 varies strongly with contact type because of the strong metal-S bond dipoles that are responsible for the Fermi level pinning. A previously published triple barrier model for molecular junctions was invoked to rationalize these results in which R0 is determined by the contact barriers, which are proportional to the size of the interfacial bond dipoles, and β is determined by the bridge barrier, E F - EHOMO. Current-voltage (I-V) characteristics obtained over a larger voltage range 0-1 V revealed a characteristic transition voltage Vtrans at which the current increased more sharply with voltage. Vtrans values were generally >0.5 V and were well correlated with the bridge barrier EF - EHOMO. Overall, the combination of electronic structure determination by UPS with length- and work function-dependent transport measurements provides a remarkably comprehensive picture of tunneling transport in molecular junctions based on oligoacenes.
- Kim, Bongsoo,Choi, Seong Ho,Zhu,Frisbie, C. Daniel
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supporting information; experimental part
p. 19864 - 19877
(2012/01/31)
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- β-Cyclodextrin dimers as potential tumor pretargeting agents
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A β-cyclodextrin dimer binds a di-tert-butylbenzyl-Cucyclen with high affinity, demonstrating potential as a receptor/ligand system for tumor pretargeting with monoclonal antibodies.
- Edwards,Reichert,D'Avignon,Welch
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p. 1312 - 1313
(2007/10/03)
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- Preparation of 2-chloro-5-methyl-pyridine
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A process for the preparation of 2-chloro-5-methylpyridine of the formula STR1 which comprises reacting 3-methyl-pyridine-1-oxide of the formula STR2 with a chlorinating agent of the formula STR3 in which R1 represents alkyl, halogenoalkyl, cycloalkyl, optionally substituted aryl, NR2 R3 or OR4 in which R2 and R3 individually represent alkyl, cycloalkyl or aryl or together represent alkanediyl or oxaalkanediyl and R4 represents alkyl, cycloalkyl or optionally substituted aryl, in the presence of a basic organic nitrogen compound and in the presence of a diluent at a temperature between about -20° C. and +150° C.
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- SYNTHESIS AND SOME TRANSFORMATIONS OF (2,7-NAPHTHYLENEDITHIO)- AND (2,6-NAPHTHYLENEDITHIO)DIACETIC ACID
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(2,7-Naphthylenedithio)- and (2,6-naphthylenedithio)diacetic acids were obtained from 2,7- and 2,6-naphthalenedisulfonic acids respectively and were oxidized to (2,7-naphthylenedisulfonyl)diacetic acids with hydrogen peroxide in acetic acid.The nitration of (2,6-naphthylenedithio)diacetic acid leads to the formation of (1,5-dinitro-2,6-naphthylenedithio)diacetic acid.
- Lisitsyn, V. N.,Kukalenko, L. S.,T-sat-sakis, A. M.
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p. 145 - 148
(2007/10/02)
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