共查询到20条相似文献,搜索用时 15 毫秒
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Shahar Dery Suhong Kim Gabriele Tomaschun David Haddad Dr. Albano Cossaro Dr. Alberto Verdini Dr. Luca Floreano Prof. Thorsten Klüner Prof. F. Dean Toste Dr. Elad Gross 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(66):15067-15072
The formation of flexible self-assembled monolayers (SAMs) in which an external trigger modifies the geometry of surface-anchored molecules is essential for the development of functional materials with tunable properties. In this work, it is demonstrated that NO2-functionalized N-heterocyclic carbene molecules (NHCs), which were anchored on Au (111) surface, change their orientation from tilted into flat-lying position following trigger-induced reduction of their nitro groups. DFT calculations identified that the energetic driving force for reorientation was the lower steric hindrance and stronger interactions between the chemically reduced NHCs and the Au surface. The trigger-induced changes in the NHCs′ anchoring geometry and chemical functionality modified the work function and the hydrophobicity of the NHC-decorated Au surface, demonstrating the impact of a chemically tunable NHC-based SAM on the properties of the metal surface. 相似文献
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Ya-Wen Zhang Dr. Rajorshi Das Yang Li Prof. Dr. Yao-Yu Wang Prof. Dr. Ying-Feng Han 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(21):5472-5479
The metal-controlled self-assembly of organometallic molecular cylinders from a series of imidazo[1,5-a]pyridine-based tris-NHC ligands is described in this report. The imidazo[1,5-a]pyridinium salts H3- L (PF6)3 ( L = 4 a – 4 c ) were treated with 1.5 equivalents of Ag2O to yield the trinuclear AgI hexacarbene cages [Ag3( L )2](PF6)3 ( L = 4 a – 4 c ), in which three AgI are sandwiched between the two tricarbene ligands. The silver(I) complexes [Ag3( L )2](PF6)3 underwent a facile transmetalation reaction in the presence of 3 equivalents of [AuCl(tht)] (tht=tetrahydrothiophene) to furnish the trinuclear AuI cylinder-like cages [Au3( L )2](PF6)3 ( L = 4 a – 4 c ) without destruction of the metallosupramolecular structure. The new hexacarbene assemblies feature a large cavity that can easily accommodate a molecule of dimethyl sulfoxide as molecular guest. This is the first study of a unique “host–guest” system containing an organometallic cylinder-like cage derived exclusively from poly-NHC ligands. 相似文献
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Dr. Deepa Krishnan Dr. Sumod A. Pullarkat Meiyi Wu Dr. Yongxin Li Prof. Pak‐Hing Leung 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(17):5468-5475
Palladium and platinum complexes containing a sulfur‐functionalised N‐heterocyclic carbene (S‐NHC) chelate ligand have been synthesised. The absolute conformations of these novel organometallic S‐NHC chelates were determined by X‐ray structural analyses and solution‐phase 2D 1H–1H ROESY NMR spectroscopy. The structural studies revealed that the phenyl substituents on the stereogenic carbon atoms invariably take up the axial positions on the Pd‐C‐S coordination plane to afford a skewed five‐membered ring structure. All of the chiral complexes are structurally rigid and stereochemically locked in a chiral ring conformation that is either (Rs,S,R)‐λ or (Ss,R,R)‐δ in both the solid state and solution. 相似文献
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First N‐Heterocyclic Carbenes Relying on the Triazolone Structural Motif: Syntheses,Modifications and Reactivity 下载免费PDF全文
Markus Jonek Janina Diekmann Prof. Dr. Christian Ganter 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(44):15759-15768
4‐Phenylsemicarbazide and 1,5‐diphenylcarbazide are suitable starting materials for the syntheses of N‐heterocyclic carbene (NHC) compounds with new backbone structures. In the first case, cyclisation and subsequent methylation leads to a cationic precursor whose deprotonation affords the triazolon‐ylidene 2 , which was converted to the corresponding sulfur and selenium adducts and a range of metal complexes. In contrast, cyclisation of diphenylcarbazide affords a neutral betain‐type NHC‐precursor 7 , which is not in equilibrium with its carbene tautomer 7a . Precursor 7 can either be deprotonated to give the anionic NHC 8 or methylated at the N or O atom of the backbone resulting in two isomeric cationic species 16 and 20 . Deprotonation of the latter two provides neutral NHC compounds with a carboxamide or carboximidate backbone, respectively. The ligand properties of the new NHC compounds were evaluated by IR and 77Se NMR spectroscopy. Tolman electronic parameter (TEP) values range from 2050 to 2063 cm?1 with the anionic NHC 8 being the best overall donor. 相似文献
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Gold-coated atomic force microscope (AFM) tips functionalized with amine-, hydroxyl-, carboxylic acid-, and methyl-terminated alkanethiol molecules were used to probe the adhesive forces of polystyrene and poly(acrylic acid) films in dry air (relative humidity < 0.5%). X-ray photoelectron spectroscopy (XPS) and contact angle measurements confirmed the quality and uniformity of similarly treated gold surfaces and the polymer films. XPS indicated that the amine-functionalized thiol films were protonated and comprised of multilayers. Contact angle data were used to calculate surface free energies, and DMT theory yielded the works of adhesion and interfacial free energies for the tip-substrate combinations. In the case of polystyrene, the work of adhesion followed the order methyl > carboxylic acid > hydroxyl > amine. For poly(acrylic acid), the observed order was hydroxyl > amine > carboxylic acid > methyl. 相似文献
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Ursula Schmelmer Anne Paul Alexander Küller Rainer Jordan Armin Gölzhäuser Michael Grunze Abraham Ulman 《Macromolecular Symposia》2004,217(1):223-230
Self-assembled monolayers of 4′-nitro-4-mercaptobiphenyl were modified by electron beam irradiation and diazotization to create a surface-bond asymmetric azo initiator for the surface-initiated polymerization (SIP). The effect of different reaction conditions upon the thermally and photochemical initiated SIP was investigated. 相似文献
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Dr. Franck Ulm Dr. Yann Cornaton Dr. Jean-Pierre Djukic Prof. Michael J. Chetcuti Prof. Vincent Ritleng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(41):8916-8925
The pentamethylcyclopentadienyl N-heterocyclic carbene nickel complex [Ni(η5-C5Me5)Cl(IMes)] (IMes=1,3-dimesitylimidazol-2-ylidene) efficiently catalyses the anti-Markovnikov hydroboration of alkenes with catecholborane in the presence of a catalytic amount of potassium tert-butoxide, and joins the very exclusive club of nickel catalysts for this important transformation. Interestingly, the regioselectivity can be reversed in some cases by using pinacolborane instead of catecholborane. Mechanistic investigations involving control experiments, 1H and 11B NMR spectroscopy, cyclic voltammetry, piezometric measurements and DFT calculations suggest an initial reduction of the NiII precursor to a NiI active species with the concomitant release of H2. The crucial role of the alkoxo-catecholato-borohydride species resulting from the reaction of potassium tert-butoxide with catecholborane in the formation of an intermediate nickel-hydride species that would then be reduced to the NiI active species, is highlighted. 相似文献
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Thomas Leitner Gernot Friedbacher Thomas Vallant Helmuth Brunner Ulrich Mayer Helmuth Hoffmann 《Mikrochimica acta》2000,133(1-4):331-336
Self-assembled monolayers of octadecylsiloxane were prepared and characterized by atomic force microscopy and ellipsometry.
Parameters, like the residual water concentration of the solvent and the solution age, that affect both the surface coverage
and the order of the film were investigated. Besides ex-situ measurements, also in-situ atomic force microscopy was used to
characterize the growth and the kinetics of the adsorption process. Furthermore, self-assembly of organic films was used as
a model system for studying the influence of the measurement process on in-situ experiments in the AFM liquid cell. 相似文献
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含酰胺结构的巯基自组装膜的设计与结构表征 总被引:11,自引:0,他引:11
提出了一种简便通用的合成巯基化合物的途径,以分子中的羧基CO2H为起始基团,与2-流基乙胺的氨基选择性缩合;合成了一系列具有RC(O)NHCH2CH2SH(R分别为偶氯苯衍生物,双炔衍生物及直链烷基)结构的化合物,并用接触角测量,电化学和掠角反射红外光谱(GIR-IR)等手段对这些化合物在金表面形成的自组装单分子膜进行了表征。发现4-(N-(2‘-巯基已基))酰胺偶氮苯的自组装膜表现出良好的电活性,电化学测定表面浓度为4.21×10(-10)mol·cm(-2).当R为烷基链时,随烷基链的增长,膜的致密度与有序度增加GIR-IR证明在自组装腹中CH3(CH2)6C(O)NHCH2CH2SH的C=O和N-H键与Au表面平行,分子轴线与Au表面近似垂直. 相似文献