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Remón P Hammarson M Li S Kahnt A Pischel U Andréasson J 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(23):6492-6500
Photochromic spiropyrans modified with fluorophores were investigated as molecular platforms for the achievement of fluorescence switching through modulation of energy transfer. The dyads were designed in such a way that energy transfer is only observed for the open forms of the photochrome (merocyanine and protonated merocyanine), whereas the closed spiropyran is inactive as an energy acceptor. This was made possible through a deliberate choice of fluorophores (4‐amino‐1,8‐naphthalimide, dansyl, and perylene) that produce zero spectral overlap with the spiro form and considerable overlap for the merocyanine forms. From the Förster theory, energy transfer is predicted to be highly efficient and in some cases of 100 % efficiency. The combined switching by photonic (light of λ>530 nm) and chemical (base) inputs enabled the creation of a sequential logic device, which is the basic element of a keypad lock. Furthermore, in combination with an anthracene‐based acidochromic fluorescence switch, a reversible logic device was designed. This enables the unambiguous coding of different input combinations through multicolour fluorescence signalling. All devices can be conveniently reset to their initial states and repeatedly cycled. 相似文献
13.
Let X be a smooth projective curve over a perfect field of characteristic p>0 and G a finite group of automorphism of X. Let ν(X,G) be the characteristic of the versal equivariant deformation ring R(X,G) of (X,G). When the ramification is weak (i.e., all second ramification groups are trivial), we prove that ν(X,G) ∈ {0,p} and we compute R(X,G).
Résumé Soit X une courbe projective lisse sur un corps parfait de caractéristique p>0 et G un groupe fini d'automorphismes de X. Nous considérons la caractéristique ν(X,G) de l'anneau versel R(X,G) de déformations équivariantes de (X,G). Dans le cas d'une ramification faible (où tous les seconds groupes de ramification sont triviaux), nous démontrons que ν(X,G) ∈ {0,p} et nous calculons R(X,G).相似文献
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15.
Koudia M Abel M Maurel C Bliek A Catalin D Mossoyan M Mossoyan JC Porte L 《The journal of physical chemistry. B》2006,110(20):10058-10062
The adsorption and ordering of zinc phthalocyanine (ZnPc) and octachloro zinc phthalocyanine (ZnPcCl(8)) on an Ag(111) surface is studied in situ by scanning tunneling microscopy under ultrahigh vacuum. Two-dimensional self-assembled supramolecular domains are observed for these two molecules. We show how substituting chlorine atoms for half of the peripheral hydrogen atoms on ZnPc influences the self-assembly mechanisms. While intermolecular interactions are dominated by van der Waals forces in ZnPc molecular networks, ZnPcCl(8) molecular packing undergoes a sequential phase evolution driven by the creation of C-Cl...H-C hydrogen bonds between adjacent molecules. At the end of this evolution, the final molecular assembly involves all possible hydrogen bonds. Our study also reveals the influence of molecule-substrate interactions through the presence of fault lines generating a stripe structure in the molecular film. 相似文献
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17.
Schwan KC Adolf A Thoms C Zabel M Timoshkin AY Scheer M 《Dalton transactions (Cambridge, England : 2003)》2008,(37):5054-5058
The halogenation of Lewis-acid/base-stabilised phosphanylboranes () and arsanylboranes () with CX(4) (X = Cl, Br) leads selectively to the substitution of both protons at the pentel atom and the new compounds [(CO)(5)W(X(2)PBH(2).NMe(3))] (: X = Cl, : X = Br) and [(CO)(5)W(X(2)AsBH(2).NMe(3))] (: X = Cl, : X = Br), respectively, are obtained. The new products were comprehensively characterised by spectroscopic methods and by X-ray crystallography. While compounds and show an antiperiplanar arrangement of the Lewis acid (W(CO)(5)) and the Lewis base (NMe(3)) in the solid state, a synclinal arrangement in and , respectively, was observed. Computational calculations of the optimised antiperiplanar and synclinal geometries of the compounds and in the gas phase slightly favour the antiperiplanar arrangement of the Lewis acid and the Lewis base for both compounds. 相似文献
18.
Identification of HcgC as a SAM‐Dependent Pyridinol Methyltransferase in [Fe]‐Hydrogenase Cofactor Biosynthesis 下载免费PDF全文
Dr. Takashi Fujishiro Liping Bai Dr. Tao Xu Dr. Xiulan Xie Dr. Michael Schick Jörg Kahnt Prof. Dr. Michael Rother Prof. Dr. Xile Hu Dr. Ulrich Ermler Dr. Seigo Shima 《Angewandte Chemie (International ed. in English)》2016,55(33):9648-9651
Previous retrosynthetic and isotope‐labeling studies have indicated that biosynthesis of the iron guanylylpyridinol (FeGP) cofactor of [Fe]‐hydrogenase requires a methyltransferase. This hypothetical enzyme covalently attaches the methyl group at the 3‐position of the pyridinol ring. We describe the identification of HcgC, a gene product of the hcgA‐G cluster responsible for FeGP cofactor biosynthesis. It acts as an S‐adenosylmethionine (SAM)‐dependent methyltransferase, based on the crystal structures of HcgC and the HcgC/SAM and HcgC/S‐adenosylhomocysteine (SAH) complexes. The pyridinol substrate, 6‐carboxymethyl‐5‐methyl‐4‐hydroxy‐2‐pyridinol, was predicted based on properties of the conserved binding pocket and substrate docking simulations. For verification, the assumed substrate was synthesized and used in a kinetic assay. Mass spectrometry and NMR analysis revealed 6‐carboxymethyl‐3,5‐dimethyl‐4‐hydroxy‐2‐pyridinol as the reaction product, which confirmed the function of HcgC. 相似文献
19.
Karl-Christian Schwan Ulf Vogel Ariane Adolf M. Zabel Manfred Scheer 《Journal of organometallic chemistry》2009,694(7-8):1189-1194
The reaction pattern of the Lewis-acid/base stabilised phosphanylborane [(CO)5W(H2PBH2 · NMe3)] (1) with elemental halogens is comprehensively studied. The reaction with iodine and bromine leads to a selective halogenation at the tungstencarbonyl moiety under formation of [WX2(CO)4(H2PBH2 · NMe3)] (X = I (2), Br (3)). Whereas 2 is a stable product the brominated compound 3 dimerises easily to [WBr2(CO)3(H2PBH2 · NMe3)]2 (4) under lost of CO. The CO elimination reaction of 3 is extensively studied. If 3 is reacted with [Et4N][Br] the ionic compound [Et4N][WBr3(CO)3(H2PBH2 · NMe3)] (5) is formed. Otherwise, if 3 is combined with the donor ligand [H2PBH2 · NMe3], the complex [WBr2(CO)3(H2PBH2 · NMe3)2] (6) is obtained. Compounds 2–6 are comprehensively characterised by X-ray diffraction analysis, NMR, and IR spectroscopy. 相似文献
20.
Aline Maisse-François Laurine Azor Anne-Laure Schmitt Ariane Coquel Lydia Brelot Richard Welter Stéphane Bellemin-Laponnaz Samuel Dagorne 《Journal of organometallic chemistry》2012,696(26):4248-4256
The present contribution describes the synthesis and structural characterization of structurally diverse organoaluminum species supported by variously substituted aminophenolate-type ligands: these Al complexes are all derived from the reaction of AlMe3 with aminophenols 2-CH2NH(R)-C6H3OH (1a, R = mesityl (Mes); 1b, R = 2,6-di-isopropylphenyl (Diip)) and 2-CH2NH(R)-4,6-tBu2-C6H2OH (1c, R = Mes; 1d, R = Diip). The low temperature reaction of AlMe3 with 1a–b readily affords the corresponding Al dimeric species [μ-η1,η1-N,O-{2-CH2NH(R)-C6H4O}]2Al2Me4 (2a–b), consisting of twelve-membered ring aluminacycles with two μ-η1,η1-N,O-aminophenolate units, as determined by X-ray crystallographic studies. Heating a toluene solution of 2a (80 °C, 3 h) affords the quantitative and direct formation of the dinuclear aluminium complex Al[η2-N; μ,η2-O-{2-CH2N(Mes)-C6H4O}](AlMe2) (4a) while species 2b, under the aforementioned conditions, affords the formation of the Al dimeric species [η2-N,O-{2-CH2N(Dipp)-C6H4O}AlMe]2 (3b), as deduced from X-ray crystallography for both 3b and 4a. In contrast, the reaction of bulky aminophenol pro-ligands 1c–d with AlMe3 afford the corresponding monomeric Al aminophenolate chelate complexes η2-N,O-{2-CH2NH(R)-4,6-tBu2-C6H2O}AlMe2 (5c–d; R = Mes, Diip; Scheme 3) as confirmed by X-ray crystallographic analysis in the case of 5d. Subsequent heating of species 5c–d yields, via a methane elimination route, the corresponding Al-THF amido species η2-N,O-{2-CH2N(R)-4,6-tBu2-C6H2O}Al(Me)(THF) (6c–d; R = Mes, Diip). Compounds 6c–6d, which are of the type {X2}Al(R)(L) (L labile), may well be useful as novel well-defined Lewis acid species of potential use for various chemical transformations. Overall, the sterics of the aminophenol backbone and, to a lesser extent, the reaction conditions that are used for a given ligand/AlMe3 set essentially govern the rather diverse “structural” outcome in these reactions, with a preference toward the formation of mononuclear Al species (i.e. species 5c–d and 6c–d) as the steric demand of the chelating N,O-ligand increases. 相似文献