- Conformation, and Charge Tunneling through Molecules in SAMs
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This paper demonstrates that the molecular conformation (in addition to the composition and structure) of molecules making up self-assembled monolayers (SAMs) influences the rates of charge tunneling (CT) through them, in molecular junctions of the form AuTS/S(CH2)2CONR1R2//Ga2O3/EGaIn, where R1 and R2 are alkyl chains of different length. The lengths of chains R1 and R2 were selected to influence the conformations and conformational homogeneity of the molecules in the monolayer. The conformations of the molecules influence the thickness of the monolayer (i.e. tunneling barrier width) and their rectification ratios at ±1.0 V. When R1 = H, the molecules are well ordered and exist predominantly in trans-extended conformations. When R1 is an alkyl group (e.g., R1 H), however, their conformations can no longer be all-trans-extended, and the molecules adopt more gauche dihedral angles. This change in the type of conformation decreases the conformational order and influences the rates of tunneling. When R1 = R2, the rates of CT decrease (up to 6.3×), relative to rates of CT observed through SAMs having the same total chain lengths, or thicknesses, when R1 = H. When R1 H R2, there is a weaker correlation (relative to that when R1 = H or R1 = R2) between current density and chain length or monolayer thickness, and in some cases the rates of CT through SAMs made from molecules with different R2 groups are different, even when the thicknesses of the SAMs (as determined by XPS) are the same. These results indicate that the thickness of a monolayer composed of insulating, amide-containing alkanethiols does not solely determine the rate of CT, and rates of charge tunneling are influenced by the conformation of the molecules making up the junction.
- Belding, Lee,Root, Samuel E.,Li, Yuan,Park, Junwoo,Baghbanzadeh, Mostafa,Rojas, Edwin,Pieters, Priscilla F.,Yoon, Hyo Jae,Whitesides, George M.
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p. 3481 - 3493
(2021/03/08)
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- Nickel-catalysed reductive amination with hydrosilanes
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That's just silyl! Selective nickel-catalyzed reductive amination of aldehydes under hydrosilylation conditions is achieved by using a one pot, two step procedure. By using an insitu-generated catalyst (5mol%) from Ni(OAc)2 and tricyclohexylphosphine with tetramethyldisiloxane (TMDS) as the hydrosilane at 70°C, the corresponding secondary amines were obtained in moderate to good isolated yields.
- Zheng, Jianxia,Roisnel, Thierry,Darcel, Christophe,Sortais, Jean-Baptiste
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p. 2861 - 2864
(2013/10/21)
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- Direct access to pop-type osmium(II) and osmium(IV) complexes: Osmium a promising alternative to ruthenium for the synthesis of imines from alcohols and amines
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An easy and direct access to POP-type osmium(II) and osmium(IV) complexes, including OsH4{dbf(PiPr2)2} (dbf(PiPr2)2 = 4,6-bis(diisopropylphosphine) dibenzofuran), is reported. This tetrahydride derivative is an efficient catalyst for the selective formation of imines from alcohols and amines with liberation of H2, proving that osmium is a promising alternative to ruthenium for catalysis.
- Esteruelas, Miguel A.,Honczek, Nicole,Olivan, Montserrat,Onate, Enrique,Valencia, Marta
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scheme or table
p. 2468 - 2471
(2011/06/27)
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- Palladium catalyzed N-alkylation of amines with alcohols
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An iron oxide immobilized palladium catalyst was prepared for the N-alkylation of amines with alcohols under base and organic ligand free conditions. Applying the optimized reaction conditions, the coupling reactions of amines and alcohols with various structures could be realized with up to 99% isolated yields. The catalysts were studied by XRD, BET, and XPS and the mechanism was studied by DFT calculations.
- Zhang, Yan,Qi, Xiujuan,Cui, Xinjiang,Shi, Feng,Deng, Youquan
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supporting information; experimental part
p. 1334 - 1338
(2011/03/22)
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