共查询到20条相似文献,搜索用时 15 毫秒
1.
Kang Cui Kunal S. Mali Dongqing Wu Xinliang Feng Klaus Müllen Michael Walter Steven De Feyter Stijn F. L. Mertens 《Angewandte Chemie (International ed. in English)》2020,59(33):14049-14053
Reported here is a molecular dipole that self‐assembles into highly ordered patterns at the liquid‐solid interface, and it can be switched at room temperature between a bright and a dark state at the single‐molecule level. Using a scanning tunneling microscope (STM) under suitable bias conditions, binary information can be written at a density of up to 41 Tb cm?2 (256 Tb/in2). The written information is stable during reading at room temperature, but it can also be erased at will, instantly, by proper choice of tunneling conditions. DFT calculations indicate that the contrast and switching mechanism originate from the stacking sequence of the molecular dipole, which is reoriented by the electric field between the tip and substrate. 相似文献
2.
Surface‐Confined Self‐Assembled Janus Tectons: A Versatile Platform towards the Noncovalent Functionalization of Graphene 下载免费PDF全文
Dr. Ping Du Maud Jaouen Dr. Amandine Bocheux Dr. Cyril Bourgogne Zheng Han Dr. Vincent Bouchiat Dr. David Kreher Dr. Fabrice Mathevet Dr. Céline Fiorini‐Debuisschert Dr. Fabrice Charra Prof. André‐Jean Attias 《Angewandte Chemie (International ed. in English)》2014,53(38):10060-10066
A general strategy for simultaneously generating surface‐based supramolecular architectures on flat sp2‐hybridized carbon supports and independently exposing on demand off‐plane functionality with controlled lateral order is highly desirable for the noncovalent functionalization of graphene. Here, we address this issue by providing a versatile molecular platform based on a library of new 3D Janus tectons that form surface‐confined supramolecular adlayers in which it is possible to simultaneously steer the 2D self‐assembly on flat C(sp2)‐based substrates and tailor the external interface above the substrate by exposure to a wide variety of small terminal chemical groups and functional moieties. This approach is validated throughout by scanning tunneling microscopy (STM) at the liquid–solid interface and molecular mechanics modeling studies. The successful self‐assembly on graphene, together with the possibility to transfer the graphene monolayer onto various substrates, should considerably extend the application of our functionalization strategy. 相似文献
3.
Francesca Matino Dr. Valentina Arima Dr. Manuel Piacenza Dr. Fabio Della Sala Dr. Giuseppe Maruccio Dr. Ray J. Phaneuf Prof. Roberta Del Sole Dr. Giuseppe Mele Dr. Giuseppe Vasapollo Prof. Giuseppe Gigli Prof. Roberto Cingolani Prof. Ross Rinaldi Prof. 《Chemphyschem》2009,10(15):2633-2641
Self‐assembled donor/acceptor dyads are of current interest as they are biomimetic to the natural photosynthetic conversion system. Herein, we present an ultrahigh‐vacuum scanning tunneling microscopy and scanning tunneling spectroscopy (UHV‐STM/STS) study of ex situ self‐assembled supramolecular dyads consisting of fulleropyrrolidines (PyC2C60) axially ligated to zinc(II) tetraphenylporphyrin (ZnTPP), self organized on a 4‐aminothiophenol (4‐ATP) self‐assembled monolayer on gold(111). These dyads show both bias‐polarity‐dependent apparent height in STM images and highly rectifying behavior in tunneling spectroscopy. First‐principles density functional theory calculations clarify the conformational and electronic properties of the 4‐ATP/ZnTPP/PyC2C60 system. Interestingly, we find easier tunneling for electrons moving from the acceptor side of the dyads to the donor side, in the inverse‐rectifying sense with respect to previously reported molecular rectifiers. Such behavior cannot be explained as an elastic resonant tunneling process, but it can by using a model based on the Aviram–Ratner mechanism. 相似文献
4.
Dr. Daniel Wegner Dr. Cristian A. Strassert 《Angewandte Chemie (International ed. in English)》2015,54(3):786-791
Frontier molecular orbitals can be visualized and selectively set to achieve blue phosphorescent metal complexes. For this purpose, the HOMOs and LUMOs of tridentate PtII complexes were measured using scanning tunneling microscopy and spectroscopy. The introduction of electron‐accepting or ‐donating moieties enables independent tuning of the frontier orbital energies, and the measured HOMO–LUMO gaps are reproduced by DFT calculations. The energy gaps correlate with the measured and the calculated energies of the emissive triplet states and the experimental luminescence wavelengths. This synergetic interplay between synthesis, microscopy, and spectroscopy enabled the design and realization of a deep‐blue triplet emitter. Finding and tuning the electronic “set screws” at molecular level constitutes a useful experimental method towards an in‐depth understanding and rational design of optoelectronic materials with tailored excited state energies and defined frontier‐orbital properties. 相似文献
5.
《Surface and interface analysis : SIA》2018,50(6):674-678
The cooperative effect of hydrogen and halogen bonds on the 2‐dimensional molecular arrangement of highly oriented pyrolytic graphite has been studied by scanning tunneling microscopy. The scanning tunneling microscopy observations demonstrate that the self‐assembled hydrogen‐bonded molecular chicken‐wire networks of trimesic acid have been significantly transformed after annealing and the introduction of tribromobenzene guest molecules. Bromine atoms and carboxyl groups were found to form 2 different multicomponent structures via hydrogen and halogen bonds. Owing to the effect of halogen and hydrogen bonds, tribromobenzene with trimesic acid formed the 3‐fold symmetry networks. 相似文献
6.
Lin Wang Dr. Zhong‐Liang Gong Shu‐Ying Li Prof. Wenjing Hong Prof. Yu‐Wu Zhong Prof. Dong Wang Prof. Li‐Jun Wan 《Angewandte Chemie (International ed. in English)》2016,55(40):12393-12397
A series of self‐complementary ureido pyrimidinedione (UPy) derivatives modified with different aurophilic anchoring groups were synthesized. Their electron transport properties through the quadruple hydrogen bonds in apolar solvent were probed employing the scanning tunneling microscopy break junction (STMBJ) technique. The molecule terminated with a thiol shows the optimal electron transport properties, with a statistical conductance value that approaches 10?3 G0. The 1H NMR spectra and control experiments verify the formation of quadruple hydrogen bonds, which can be effectively modulated by the polarity of the solvent environment. These findings provide a new design strategy for supramolecular circuit elements in molecular electronics. 相似文献
7.
Electrochemical Investigation of Cytochrome c Immobilized onto Self‐Assembled Monolayer of Captopril
The electrochemical behavior of cytochrome c (cyt‐c) that was electrostatically immobilized onto a self‐assembled monolayer (SAM) of captopril (capt) on a gold electrode has been investigated. Cyclic voltammetry, scanning electrochemical microscopy (SECM) and electrochemical impedance spectroscopy were employed to evaluate the blocking property of the capt SAM. SECM was used to measure the bimolecular electron transfer (ET) kinetics (kBI) between a solution‐based redox probe and the immobilized protein. In addition, the tunneling ET between the immobilized protein and the underlying gold electrode was calculated. A kBI value of (5.0±0.6)×108 mol?1 cm3 s?1 for the bimolecular ET and a standard tunneling rate constant (k0) of 46.4±0.2 s?1 for the tunneling ET have been obtained. 相似文献
8.
Nanoscale Chemical Imaging of Reversible Photoisomerization of an Azobenzene‐Thiol Self‐Assembled Monolayer by Tip‐Enhanced Raman Spectroscopy 下载免费PDF全文
Li‐Qing Zheng Xing Wang Feng Shao Prof. Dr. Martin Hegner Prof. Dr. Renato Zenobi 《Angewandte Chemie (International ed. in English)》2018,57(4):1025-1029
An understanding of the photoisomerization mechanism of molecules bound to a metal surface at the molecular scale is required for designing photoswitches at surfaces. It has remained a challenge to correlate the surface structure and isomerization of photoswitches at ambient conditions. Herein, the photoisomerization of a self‐assembled monolayer of azobenzene‐thiol molecules on a Au surface was investigated using scanning tunneling microscopy and tip‐enhanced Raman spectroscopy. The unique signature of the cis isomer at 1525 cm?1 observed in tip‐enhanced Raman spectra was clearly distinct from the trans isomer. Furthermore, tip‐enhanced Raman images of azobenzene thiols after ultraviolet and blue light irradiation are shown with nanoscale spatial resolution, demonstrating a reversible conformational change. Interestingly, the cis isomers of azobenzene‐thiol molecules were preferentially observed at Au grain edges, which is confirmed by density functional theory. 相似文献
9.
Synthesis of a Neutral Mixed‐Valence Diferrocenyl Carborane for Molecular Quantum‐Dot Cellular Automata Applications 下载免费PDF全文
John A. Christie Ryan P. Forrest Dr. Steven A. Corcelli Dr. Natalie A. Wasio Dr. Rebecca C. Quardokus Dr. Ryan Brown Dr. S. Alex Kandel Dr. Yuhui Lu Dr. Craig S. Lent Dr. Kenneth W. Henderson 《Angewandte Chemie (International ed. in English)》2015,54(51):15448-15451
The preparation of 7‐Fc+‐8‐Fc‐7,8‐nido‐[C2B9H10]? (Fc+FcC2B9?) demonstrates the successful incorporation of a carborane cage as an internal counteranion bridging between ferrocene and ferrocenium units. This neutral mixed‐valence FeII/FeIII complex overcomes the proximal electronic bias imposed by external counterions, a practical limitation in the use of molecular switches. A combination of UV/Vis‐NIR spectroscopic and TD‐DFT computational studies indicate that electron transfer within Fc+FcC2B9? is achieved through a bridge‐mediated mechanism. This electronic framework therefore provides the possibility of an all‐neutral null state, a key requirement for the implementation of quantum‐dot cellular automata (QCA) molecular computing. The adhesion, ordering, and characterization of Fc+FcC2B9? on Au(111) has been observed by scanning tunneling microscopy. 相似文献
10.
Potential‐Dependent Adlayer Structure and Dynamics at the Ionic Liquid/Au(111) Interface: A Molecular‐Scale In Situ Video‐STM Study 下载免费PDF全文
Dr. Rui Wen Björn Rahn Prof. Dr. Olaf M. Magnussen 《Angewandte Chemie (International ed. in English)》2015,54(20):6062-6066
Room‐temperature ionic liquids are of great current interest for electrochemical applications in material and energy science. Essential for understanding the electrochemical reactivity of these systems are detailed data on the structure and dynamics of the interfaces between these compounds and metal electrodes, which distinctly differ from those in traditional electrolytes. In situ studies are presented of Au(111) electrodes in 1‐butyl‐1‐methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([BMP][TFSA]) by high‐speed scanning tunneling microscopy (video‐STM). [BMP][TFSA] is one of the best‐understood air and water stable ionic liquids. The measurements provide direct insights into the potential‐dependent molecular arrangement and surface dynamics of adsorbed [BMP]+ cations in the innermost layer on the negatively charged Au electrode surface. In particular, two distinct subsequent transitions in the adlayer structure and lateral mobility are observed with decreasing potential. 相似文献
11.
Dense or Porous Packing? Two‐Dimensional Self‐Assembly of Star‐Shaped Mono‐, Bi‐, and Terpyridine Derivatives 下载免费PDF全文
Dr. Daniel Trawny Philomena Schlexer Krista Steenbergen Prof. Dr. Jürgen P. Rabe Prof. Dr. Beate Paulus Prof. Dr. Hans‐Ulrich Reissig 《Chemphyschem》2015,16(5):949-953
The self‐assembly behavior of five star‐shaped pyridyl‐functionalized 1,3,5‐triethynylbenzenes was studied at the interface between an organic solvent and the basal plane of graphite by scanning tunneling microscopy. The mono‐ and bipyridine derivatives self‐assemble in closely packed 2D crystals, whereas the derivative with the more bulky terpyridines crystallizes with porous packing. DFT calculations of a monopyridine derivative on graphene, support the proposed molecular model. The calculations also reveal the formation of hydrogen bonds between the nitrogen atoms and a hydrogen atom of the neighboring central unit, as a small nonzero tunneling current was calculated within this region. The title compounds provide a versatile model system to investigate the role of multivalent steric interactions and hydrogen bonding in molecular monolayers. 相似文献
12.
Supramolecular Assembly through Interactions between Molecular Dipoles and Alkali Metal Ions 下载免费PDF全文
Dr. Tomoko K. Shimizu Dr. Jaehoon Jung Dr. Hiroshi Imada Dr. Yousoo Kim 《Angewandte Chemie (International ed. in English)》2014,53(50):13729-13733
Establishing a way to fabricate well‐ordered molecular structures is a necessary step toward advancement in organic optoelectronic devices. Here, we propose to use interactions between electric dipoles of molecules and alkali metal ions to form a well‐developed homogeneous monolayer of diarylethene molecules on the Cu(111) surface with the aid of NaCl co‐deposition. Scanning tunneling microscopy and density functional theory calculation results indicate that the formation of a row‐type structure occurs as a result of interactions between the Na+ ions and the diarylethene molecular dipoles, drastically changing the adsorption configuration from that without Na+. 相似文献
13.
Tobias Paintner Jonas Bjrk Ping Du Svetlana Klyatskaya Mateusz Paszkiewicz Raphael Hellwig Martin Uphoff Murat A.
ner Edoardo Cuniberto Peter S. Deimel Yi‐Qi Zhang Carlos‐Andres Palma Francesco Allegretti Mario Ruben Johannes V. Barth Florian Klappenberger 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(33):11407-11412
Reaction pathways involving quantum tunneling of protons are fundamental to chemistry and biology. They are responsible for essential aspects of interstellar synthesis, the degradation and isomerization of compounds, enzymatic activity, and protein dynamics. On‐surface conditions have been demonstrated to open alternative routes for organic synthesis, often with intricate transformations not accessible in solution. Here, we investigate a hydroalkoxylation reaction of a molecular species adsorbed on a Ag(111) surface by scanning tunneling microscopy complemented by X‐ray electron spectroscopy and density functional theory. The closure of the furan ring proceeds at low temperature (down to 150 K) and without detectable side reactions. We unravel a proton‐tunneling‐mediated pathway theoretically and confirm experimentally its dominant contribution through the kinetic isotope effect with the deuterated derivative. 相似文献
14.
Qiang Sun Liangliang Cai Yuanqi Ding Lei Xie Chi Zhang Prof. Dr. Qinggang Tan Prof. Dr. Wei Xu 《Angewandte Chemie (International ed. in English)》2015,54(15):4549-4552
Homocouplings of hydrocarbon groups including alkynyl (sp1), alkyl (sp3), and aryl (sp2) have recently been investigated on surfaces with the interest of fabricating novel carbon nanostructures/nanomaterials and getting fundamental understanding. Investigated herein is the on‐surface homocoupling of an alkenyl group which is the last elementary unit of hydrocarbons. Through real‐space direct visualization (scanning tunneling microscopy imaging) and density functional theory calculations, the two terminal alkenyl groups were found to couple into a diene moiety on copper surfaces, and is contrary to the common dimerization products of alkenes in solution. Furthermore, detailed DFT‐based transition‐state searches were performed to unravel this new reaction pathway. 相似文献
15.
Shantanu Mishra Doreen Beyer Kristjan Eimre Ricardo Ortiz Joaquín Fernndez‐Rossier Reinhard Berger Oliver Grning Carlo A. Pignedoli Roman Fasel Xinliang Feng Pascal Ruffieux 《Angewandte Chemie (International ed. in English)》2020,59(29):12041-12047
Triangular zigzag nanographenes, such as triangulene and its π‐extended homologues, have received widespread attention as organic nanomagnets for molecular spintronics, and may serve as building blocks for high‐spin networks with long‐range magnetic order, which are of immense fundamental and technological relevance. As a first step towards these lines, we present the on‐surface synthesis and a proof‐of‐principle experimental study of magnetism in covalently bonded triangulene dimers. On‐surface reactions of rationally designed precursor molecules on Au(111) lead to the selective formation of triangulene dimers in which the triangulene units are either directly connected through their minority sublattice atoms, or are separated via a 1,4‐phenylene spacer. The chemical structures of the dimers have been characterized by bond‐resolved scanning tunneling microscopy. Scanning tunneling spectroscopy and inelastic electron tunneling spectroscopy measurements reveal collective singlet–triplet spin excitations in the dimers, demonstrating efficient intertriangulene magnetic coupling. 相似文献
16.
Xiang Wang Zhen‐Feng Cai Yu‐Qi Wang Ya‐Chen Feng Hui‐Juan Yan Dong Wang Li‐Jun Wan 《Angewandte Chemie (International ed. in English)》2020,59(37):16098-16103
We report a molecular investigation of a cobalt phthalocyanine (CoPc)‐catalyzed CO2 reduction reaction by electrochemical scanning tunneling microscopy (ECSTM). An ordered adlayer of CoPc was prepared on Au(111). Approximately 14 % of the adsorbed species appeared with high contrast in a CO2‐purged electrolyte environment. The ECSTM experiments indicate the proportion of high‐contrast species correlated with the reduction of CoIIPc (?0.2 V vs. saturated calomel electrode (SCE)). The high‐contrast species is ascribed to the CoPc‐CO2 complex, which is further confirmed by theoretical simulation. The sharp contrast change from CoPc‐CO2 to CoPc is revealed by in situ ECSTM characterization of the reaction. Potential step experiments provide dynamic information for the initial stage of the reaction, which include the reduction of CoPc and the binding of CO2, and the latter is the rate‐limiting step. The rate constant of the formation and dissociation of CoPc‐CO2 is estimated on the basis of the in situ ECSTM experiment. 相似文献
17.
Raffael Schwan Chen Qu Devendra Mani Nitish Pal Lex vanderMeer Britta Redlich Claude Leforestier Joel M. Bowman Gerhard Schwaab Martina Havenith 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(37):13253-13260
Using the helium nanodroplet isolation setup at the ultrabright free‐electron laser source FELIX in Nijmegen (BoHeNDI@FELIX), the intermolecular modes of water dimer in the frequency region from 70 to 550 cm?1 were recorded. Observed bands were assigned to donor torsion, acceptor wag, acceptor twist, intermolecular stretch, donor torsion overtone, and in‐plane and out‐of‐plane librational modes. This experimental data set provides a sensitive test for state‐of‐the‐art water potentials and dipole moment surfaces. Theoretical calculations of the IR spectrum are presented using high‐level quantum and approximate quasiclassical molecular dynamics approaches. These calculations use the full‐dimensional ab initio WHHB potential and dipole moment surfaces. Based on the experimental data, a considerable increase of the acceptor switch and a bifurcation tunneling splitting in the librational mode is deduced, which is a consequence of the effective decrease in the tunneling barrier. 相似文献
18.
Dr. Ayuk M. Ako Dr. Mohammad Sahabul Alam Mostafizur Rahman Dr. Jonathan P. Hill Dr. Noelia M. Sanchez‐Ballester Dr. Katsuhiko Ariga Dr. Gernot Buth Dr. Christopher E. Anson Prof. Dr. Annie K. Powell 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(51):16419-16425
The synthesis and structures of the N‐[(2‐hydroxy‐3‐methyl‐5‐dodecylphenyl)methyl]‐N‐(carboxymethyl)glycine disodium salt (H L ) ligand and its neutral mononuclear complex [FeIII( L )(EtOH)2] ( 1 ) are reported. Structural and electronic properties of 1 were investigated by using scanning tunneling microscopy (STM) and current imaging tunneling spectroscopy (CITS) techniques. These studies reveal that molecules of 1 form well‐ordered self‐assemblies when deposited on a highly oriented pyrolytic graphite (HOPG) surface. At low concentrations, single or double chains (i.e., nanowires) of the complex were observed, whereas at high concentration the complex forms crystals and densely packed one‐dimensional structures. In STM topographies, the dimensions of assemblies of 1 found on the surface are consistent with dimensions obtained from X‐ray crystallography, which indicates the strong similarities between the crystal form and surface assembled states. Double chains are attributed to hydrogen‐bonding interactions and the molecules align preferentially along graphite defects. In the CITS image of complex 1 a strong tunneling current contrast at the positions of the metal ions was observed. These data were interpreted and reveal that the bonds coordinating the metal ions are weaker than those of the surrounding ligands; therefore the energy levels next to the Fermi energy of the molecule should be dominated by metal‐ion orbitals. 相似文献
19.
Luis M. Mateo Qiang Sun Shi‐Xia Liu Jesse J. Bergkamp Kristjan Eimre Carlo A. Pignedoli Pascal Ruffieux Silvio Decurtins Giovanni Bottari Roman Fasel Tomas Torres 《Angewandte Chemie (International ed. in English)》2020,59(3):1334-1339
On‐surface synthesis offers a versatile approach to prepare novel carbon‐based nanostructures that cannot be obtained by conventional solution chemistry. Graphene nanoribbons (GNRs) have potential for a variety of applications. A key issue for their application in molecular electronics is in the fine‐tuning of their electronic properties through structural modifications, such as heteroatom doping or the incorporation of non‐benzenoid rings. In this context, the covalent fusion of GNRs and porphyrins (Pors) is a highly appealing strategy. Herein we present the selective on‐surface synthesis of a Por–GNR hybrid, which consists of two Pors connected by a short GNR segment. The atomically precise structure of the Por–GNR hybrid has been characterized by bond‐resolved scanning tunneling microscopy (STM) and noncontact atomic force microscopy (nc‐AFM). The electronic properties have been investigated by scanning tunneling spectroscopy (STS), in combination with DFT calculations, which reveals a low electronic gap of 0.4 eV. 相似文献
20.
The accurate molecular dynamics simulation of weakly bound adhesive complexes, such as supported graphene (gr), is challenging because of the lack of an adequate interface potential. Instead of the widely used Lennard‐Jones potential for weak and long‐range interactions, we use a newly parameterized Tersoff potential for gr/Ru(0001) system. The new interfacial force field provides adequate moire superstructures in accordance with scanning tunneling microscopy images and with density functional theory (DFT) results. In particular, the corrugation of ξ ≈ 1.0 ± 0.2 Å is found that is somewhat smaller than found by DFT approaches (ξ ≈ 1.2 Å) and is close to scanning tunneling microscope measurements (ξ ≈ 0.8 ± 0.3 Å). The new potential could open the way toward large‐scale simulations of supported gr with adequate moire supercells in many fields of gr research. Moreover, the new interface potential might provide a new strategy in general for obtaining accurate interaction potentials for weakly bound adhesion in large‐scale systems in which atomic dynamics is inaccessible yet by accurate DFT calculations. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献