Supramolecular Rotor and Translator at Work: On-Surface Movement of Single Atoms (original) (raw)
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The surface diffusion of individual molecules is of paramount importance in selfassembly processes and catalytic processes. However, the fundamental understanding of molecule diffusion peculiarities considering conformations and adsorption sites remain poorly known at the atomic-scale. Here, we probe the 4'-(4-tolyl)-2,2':6',2"terpyridine adsorbed on the Au(111) herringbone structure combining scanning tunneling microscopy and atomic force microscopy. Molecules are controllably translated by electrons excitations over the reconstruction, except at elbows acting as pinning
Unidirectional molecular motor on a gold surface
Nature, 2005
Molecules capable of mimicking the function of a wide range of mechanical devices have been fabricated, with motors that can induce mechanical movement attracting particular attention 1,2 . Such molecular motors convert light or chemical energy into directional rotary or linear motion 2-10 , and are usually prepared and operated in solution. But if they are to be used as nanomachines that can do useful work, it seems essential to construct systems that can function on a surface, like a recently reported linear artificial muscle 11 . Surface-mounted rotors have been realized and limited directionality in their motion predicted 12,13 . Here we demonstrate that a light-driven molecular motor capable of repetitive unidirectional rotation 14 can be mounted on the surface of gold nanoparticles. The motor design 14 uses a chiral helical alkene with an upper half that serves as a propeller and is connected through a carbon-carbon double bond (the rotation axis) to a lower half that serves as a stator. The stator carries two thiol-functionalized 'legs', which then bind the entire motor molecule to a gold surface. NMR spectroscopy reveals that two photo-induced cis-trans isomerizations of the central double bond, each followed by a thermal helix inversion to prevent reverse rotation, induce a full and unidirectional 3608 rotation of the propeller with respect to the surface-mounted lower half of the system.
Conformation Manipulation and Motion of a Double Paddle Molecule on an Au(111) Surface
ACS Nano
The molecular conformation of a bisbinaphthyldurene (BBD) molecule is manipulated using a lowtemperature ultrahigh-vacuum scanning tunneling microscope (LT-UHV STM) on an Au(111) surface. BBD has two binaphthyl groups at both ends connected to a central durene leading to anti/syn/flat conformers. In solution, dynamic nuclear magnetic resonance indicated the fast interexchange between the anti and syn conformers as confirmed by density functional theory calculations. After deposition in a submonolayer on an Au(111) surface, only the syn conformers were observed forming small islands of self-assembled syn dimers. The syn dimers can be separated into syn monomers by STM molecular manipulations. A flat conformer can also be prepared by using a peculiar mechanical unfolding of a syn monomer by STM manipulations. The experimental STM dI/dV and theoretical elastic scattering quantum chemistry maps of the low-lying tunneling resonances confirmed the flat conformer BBD molecule STM production. The key BBD electronic states for a step-by-step STM inelastic excitation lateral motion on the Au(111) are presented requiring no mechanical interactions between the STM tip apex and the BBD. On the BBD molecular board, selected STM tip apex positions for this inelastic tunneling excitation enable the flat BBD to move controllably on Au(111) by a step of 0.29 nm per bias voltage ramp.
Constructing an Array of Anchored Single-Molecule Rotors on Gold Surfaces
Physical Review Letters, 2008
Molecular rotors with a fixed off-center rotation axis have been observed for single tetra-tert-butyl zinc phthalocyanine molecules on an Au(111) surface by a scanning tunneling microscope at LN 2 temperature. Experiments and first-principles calculations reveal that we introduce gold adatoms at the surface as the stable contact of the molecule to the surface. An off-center rotation axis is formed by a chemical bonding between a nitrogen atom of the molecule and a gold adatom at the surface, which gives them a welldefined contact while the molecules can have rotation-favorable configurations. Furthermore, these singlemolecule rotors self-assemble into large scale ordered arrays on Au(111) surfaces. A fixed rotation axis off center is an important step towards the eventual fabrication of molecular motors or generators.
Current-Driven Supramolecular Motor with In Situ Surface Chiral Directionality Switching
Nano letters, 2015
Surface-supported molecular motors are nanomechanical devices of particular interest in terms of future nanoscale applications. However, the molecular motors realized so far consist of covalently bonded groups that cannot be reconfigured without undergoing a chemical reaction. Here we demonstrate that a platinum-porphyrin-based supramolecularly assembled dimer supported on a Au(111) surface can be rotated with high directionality using the tunneling current of a scanning tunneling microscope (STM). Rotational direction of this molecular motor is determined solely by the surface chirality of the dimer, and most importantly, the chirality can be inverted in situ through a process involving an intradimer rearrangement. Our result opens the way for the construction of complex molecular machines on a surface to mimic at a smaller scale versatile biological supramolecular motors.
Moving Nanostructures: Pulse Induced Positioning of Supramolecular Assemblies
2012
For the development of nanoscale devices, the manipulation of single atoms and molecules by scanning tunneling microscopy is a well established experimental technique. However, for the construction of larger and higher order structures, it is important to move not only one adsorbate, but several at the same time. Additionally, a major issue in standard manipulation experiments is the strong mechanical interaction of the tip apex and the adsorbate, which can damage the system under investigation.
Transmitting Stepwise Rotation among Three Molecule-Gear on the Au(111) Surface
The realization of a train of molecule-gears working under the tip of a scanning tunneling microscope (STM) requires a stable anchor of each molecule to the metal surface. Such anchor can be promoted by a radical state of the molecule induced by a dissociation reaction. Our results, rationalized by density functional theory calculations, reveal that such open radical state at the cyclopentadiene core of star-shaped pentaphenylcyclopentadiene (PPCP) favors the anchoring. Furthermore, to allow the transmission of motion by STM manipulation, the molecule-gear should be equipped with specific groups facilitating the tip-molecule interactions. In our case, a tert-butyl group positioned at one tooth end of the gear benefits both the tipinduced manipulation and the monitoring of rotation. With this optimized molecular system we achieve reproducible and stepwise rotations of the single gears and transmit rotations up to three interlocked units.
STM manipulation of a subphthalocyanine double-wheel molecule on Au (111)
2012
Abstract A new class of double-wheel molecules is manipulated on a Au (111) surface by the tip of a scanning tunneling microscope (STM) at low temperature. The double-wheel molecule consists of two subphthalocyanine wheels connected by a central rotation carbon axis. Each of the subphthalocyanine wheels has a nitrogen tag to monitor its intramolecular rolling during an STM manipulation sequence.
Physical Review Letters, 2004
A novel scanning tunneling microscope manipulation scheme for a controlled molecular transport of weakly adsorbed molecules is demonstrated. Single sexiphenyl molecules adsorbed on a Ag(111) surface at 6 K are shot towards single silver-atoms by excitation with the tip. To achieve atomically straight shooting paths, an electron resonator consisting of linear standing wave fronts is constructed. The sexiphenyl manipulation signals reveal a π-ring flipping as the molecule moves from hcp to fcc site. Abinitio calculations show an incorporation of the Ag atom below the center of a π-ring. * Coressponding author, Email: hla@ohio.edu, web: www.phy.ohiou.edu/\~hla PACS: 82.37.Gk, 68.37.Ef, 33.15.Bh ___________________________________________________ The advances in scanning tunneling microscope (STM) manipulation allow probing physical/chemical properties of single molecules or construction of atomic scale structures on surfaces [1-9]. STM manipulation requires a precise control over the tip-molecule-surface junction. A weakly adsorbed molecule on a surface can be easily displaced with the STM-tip but its movement is extremely difficult to control. Most surface chemical reactions involve weakly adsorbed molecular species; however, investigations on their detailed dynamics and reactivity are hindered by instrumentation limits. Here, we have chosen weakly adsorbed sexiphenyl on Ag(111) as a model system to develop an STM manipulation scheme. Sexiphenyl (C 36 H 26 ) is composed of six π-rings connected to form a linear chain [10] and due to its potential applications in display electronic devices, sexiphenyl has been studied intensely in the past years .