STM manipulation of molecular moulds on metal surfaces (original) (raw)
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Bicomponent hydrogen-bonded nanostructures formed by two complementary molecular Landers on Au(111)
Chem. Commun., 2014
The co-adsorption of two molecular Landers equipped with functional groups capable of forming a complementary triple hydrogenbonding motif is investigated with scanning tunneling microscopy and molecular mechanics calculations. Surprisingly, the anticipated complementary motif is not realised in 2-D terrace structures, but is observed in 1-D structures at step edges where molecular conformational flexibility is confined.
Lander on Cu(211) – selective adsorption and surface restructuring by a molecular wire
Chemical Physics Letters, 2003
The large organic molecule C 90 H 98 , called Lander, has been investigated on the Cu(2 1 1) surface by low temperature scanning tunnelling microscopy (LT-STM). Different adsorption geometries, which differ in the internal conformation and the orientation of the molecule, are described. These adsorption conformations have been determined by elastic scattering quantum chemistry calculations (ESQC). For T > 120 K, adsorption at selected step edges is combined with an adsorbate induced restructuring. The reconstruction is revealed by lateral STM manipulation and could be imaged with atomic resolution. It has the form of a (3 1 1) facet. The restructured steps can be used as a guidance for lateral manipulation of large molecules.
Adsorption behavior of Lander molecules on Cu(110) studied by scanning tunneling microscopy
The Journal of Chemical Physics, 2002
The adsorption of a large organic molecule, named Lander, has been studied on a Cu͑110͒ substrate by scanning tunneling microscopy ͑STM͒. At low temperatures three different conformations of the molecule are observed on the flat surface terraces. At room temperature the Lander molecules are highly mobile and anchor preferentially to step edges. There the molecules cause a rearrangement of the Cu step atoms leading to the formation of Cu nanostructures that are adapted to the dimension of the molecule, as revealed directly by STM manipulation experiments. Upon annealing to 500 K the molecules order at higher coverages partially into small domains. In all cases the exact adsorption conformation of the molecules was identified through an interplay with elastic scattering quantum chemistry calculations.
Scanning tunneling microscopy experiments on single molecular landers
Molecular landers are molecules comprising of a central rigid molecular wire maintained above a metallic surface by organic spacers, which allows specific ultrahigh vacuum-scanning tunneling microscopy experiments to be performed at the single-molecule level. The understanding of the molecule-surface interactions, intramolecular mechanics, and the possibility to perform extremely precise tipinduced manipulation permit these molecules to be brought in contact with a nanoelectrode and the resulting electronic interaction to be analyzed in well controlled conditions. contact ͉ molecular wire ͉ nanoelectrodes ͉ single-molecule manipulation
Acs Nano, 2010
Supramolecular self-assembly on surfaces, guided by hydrogen bonding interactions, has been widely studied, most often involving planar compounds confined directly onto surfaces in a planar twodimensional (2-D) geometry and equipped with structurally rigid chemical functionalities to direct the selfassembly. In contrast, so-called molecular Landers are a class of compounds that exhibit a pronounced threedimensional (3-D) structure once adsorbed on surfaces, arising from a molecular backboard equipped with bulky groups which act as spacer legs. Here we demonstrate the first examples of extended, hydrogen-bonded surface architectures formed from molecular Landers. Using high-resolution scanning tunnelling microscopy (STM) under well controlled ultrahigh vacuum conditions we characterize both one-dimensional (1-D) chains as well as five distinct long-range ordered 2-D supramolecular networks formed on a Au(111) surface from a specially designed Lander molecule equipped with dual diamino-triazine (DAT) functional moieties, enabling complementary NH · · · N hydrogen bonding. Most interestingly, comparison of experimental results to STM image calculations and molecular mechanics structural modeling demonstrates that the observed molecular Lander-DAT structures can be rationalized through characteristic intermolecular hydrogen bonding coupling motifs which would not have been possible in purely planar 2-D surface assembly because they involve pronounced 3-D optimization of the bonding configurations. The described 1-D and 2-D patterns of Lander-DAT molecules may potentially be used as extended molecular molds for the nucleation and growth of complex metallic nanostructures.
Interaction of a long molecular wire with a nanostructured surface: Violet Landers on Cu(211)
Chemical Physics Letters, 2006
Violet Lander molecules (long molecular wires with legs) are deposited on the nanostructured Cu(2 1 1) surface at 325 K and 177 K and investigated by low temperature scanning tunnelling microscopy. Selective population of (3 1 1) steps and local surface restructuring are observed for molecules adsorbed with their axis parallel to intrinsic steps. Thanks to the good matching between molecular dimensions and surface corrugation, molecules oriented perpendicularly to the steps assume conformations which allow tunnelling also through the molecular wire. The molecular wire terminations are hence self-contacted to the Cu(2 1 1) surface native (1 1 1) and (3 1 1) step edges.
Self-assembly of strongly dipolar molecules on metal surfaces
The Journal of Chemical Physics, 2015
The role of dipole-dipole interactions in the self-assembly of dipolar organic molecules on surfaces is investigated. As a model system, strongly dipolar model molecules, p-benzoquinonemonoimine zwitterions (ZI) of type C 6 H 2 (· · · NHR) 2 (· · · O) 2 on crystalline coinage metal surfaces were investigated with scanning tunneling microscopy and first principles calculations. Depending on the substrate, the molecules assemble into small clusters, nano gratings, and stripes, as well as in two-dimensional islands. The alignment of the molecular dipoles in those assemblies only rarely assumes the lowest electrostatic energy configuration. Based on calculations of the electrostatic energy for various experimentally observed molecular arrangements and under consideration of computed dipole moments of adsorbed molecules, the electrostatic energy minimization is ruled out as the driving force in the self-assembly. The structures observed are mainly the result of a competition between chemical interactions and substrate effects. The substrate's role in the self-assembly is to (i) reduce and realign the molecular dipole through charge donation and back donation involving both the molecular HOMO and LUMO, (ii) dictate the epitaxial orientation of the adsorbates, specifically so on Cu(111), and (iii) inhibit attractive forces between neighboring chains in the system ZI/Cu(111), which results in regularly spaced molecular gratings. C 2015 AIP Publishing LLC. [http://dx.
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.