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Due to the low corrugation of the Au(111) surface, 1,4-bis(phenylethynyl)-2,5-bis(ethoxy)benzene (PEEB) molecules can form quasi interlocked lateral patterns, which are observed in scanning tunneling microscopy experiments at low temperatures. We demonstrate a multi-dimensional clustering approach to quantify the anisotropic pair-wise interaction of molecules and explain these patterns. We perform high-throughput calculations to evaluate an energy function, which incorporates the adsorption energy of single PEEB molecules on the metal surface and the intermolecular interaction energy of a pair of PEEB molecules. The analysis of the energy function reveals, that, depending on coverage density, specific types of pattern are preferred which can potentially be exploited to form one-dimensional molecular wires on Au(111).

We present a low temperature scanning tunneling microscope investigation of a prochiral thiophene-based molecule that self-assembles forming islands with different domains on the Au(111) surface. In the domains, two different conformations of the single molecule are observed, depending on a slight rotation of two adjacent bromothiophene groups. Using voltage pulses from the tip, single molecules can be switched between the two conformations. The electronic states have been measured with scanning tunneling spectroscopy, showing that the electronic resonances are mainly localized at the same positions in both conformations. Density-functional theory calculations support the experimental results. Furthermore, we observe that on Ag(111), only one configuration is present and therefore the switching effect is suppressed.

Molecular machines, and in particular molecular motors with synthetic molecular structures and fuelled by external light, voltage or chemical conversions, have recently been reported 1 , 2 , 3 , 4 , 5 , 6 . Most of these experiments are carried out in solution with a large ensemble of molecules and without access to one molecule at a time, a key point for future use of single molecular machines with an atomic scale precision. Therefore, to experiment on a single molecule-machine, this molecule has to be adsorbed on a surface, imaged and manipulated with the tip of a scanning tunnelling microscope (STM) 7 , 8 , 9 , 10 . A few experiments of this type have described molecular mechanisms in which a rotational movement of a single molecule is involved. However, until now, only uncontrolled rotations 11 , 12 , 13 or indirect signatures 14 , 15 of a rotation have been reported. In this work, we present a molecular rack-and-pinion device for which an STM tip drives a single pinion molecule at low temperature. The pinion is a 1.8-nm-diameter molecule functioning as a six-toothed wheel interlocked at the edge of a self-assembled molecular island acting as a rack. We monitor the rotation of the pinion molecule tooth by tooth along the rack by a chemical tag attached to one of its cogs.

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 tip-induced manipulation permit these molecules to be brought in contact with a nanoelectrode and the resulting electronic interaction to be analyzed in well controlled conditions.

A large dissymmetric starphene molecule, the tetrabenzo[a,c,u,w]naphtho[2,3‐l]nonaphene, was obtained by first preparing a soluble precursor which was then sublimated on a Au(111) surface in an ultra‐high vacuum. In a second step, controlled annealings from 200 °C to 275 °C initiated two successive cyclodehydrogenation steps with the formation of 3 new carbon‐carbon bonds. A second conformer was also stable enough during the annealing step to give another compound in similar yield, the benzodibenzo[7,8,9,10]naphthaceno[2,1‐h]phenanthro[9,10‐p]hexaphene. The formation of this more‐hindered species stresses the importance of strong molecule‐surface interactions during the cyclodehydrogenations steps of these large polyaromatic hydrocarbons. Two dissymmetric large starphene molecules, the tetrabenzo[4.4.2]undecastarphene and the benzodibenzo[7,8,9,10]naphthaceno[2,1‐h]phenanthro[9,10‐p]hexaphene, have been obtained in the ratio 1 : 1 by successive on‐surface cyclodehydrogenation steps on a gold surface from a sterically crowded and soluble precursor. The formation of the more hindered hexaphene species stresses the importance of strong molecule‐surface interactions during the cyclodehydrogenation steps of these large polyaromatic hydrocarbons, which can be applied as single‐molecule logic gates.

A large dissymmetric starphene molecule, the tetrabenzo[a,c,u,w]naphtho[2,3-l]nonaphene, was obtained by first preparing a soluble precursor which was then sublimated on a Au(111) surface in an ultra-high vacuum. In a second step, controlled annealings from 200 °C to 275 °C initiated two successive cyclodehydrogenation steps with the formation of 3 new carbon-carbon bonds. A second conformer was also stable enough during the annealing step to give another compound in similar yield, the benzodibenzo[7,8,9,10]naphthaceno[2,1-h]phenanthro[9,10-p]hexaphene. The formation of this more-hindered species stresses the importance of strong molecule-surface interactions during the cyclodehydrogenations steps of these large polyaromatic hydrocarbons.A large dissymmetric starphene molecule, the tetrabenzo[a,c,u,w]naphtho[2,3-l]nonaphene, was obtained by first preparing a soluble precursor which was then sublimated on a Au(111) surface in an ultra-high vacuum. In a second step, controlled annealings from 200 °C to 275 °C initiated two successive cyclodehydrogenation steps with the formation of 3 new carbon-carbon bonds. A second conformer was also stable enough during the annealing step to give another compound in similar yield, the benzodibenzo[7,8,9,10]naphthaceno[2,1-h]phenanthro[9,10-p]hexaphene. The formation of this more-hindered species stresses the importance of strong molecule-surface interactions during the cyclodehydrogenations steps of these large polyaromatic hydrocarbons.

The Cover Feature shows the evolution of scanning tunneling microscopy images during the cyclodehydrogenation of a polyaromatic hydrocarbon precursor sublimated onto an Au(111) surface under ultra‐high vacuum. This strategy allows the on‐surface preparation and study of planar large and dissymmetric starphenes that could not be prepared in solution, and may give access to families of molecular logic gates that are of interest in single‐molecule electronics. More information can be found in the Full Paper by A. Jancarik, A. Gourdon, F. Moresco, and co‐workers.

The scanning tunnelling microscope, initially invented to image surfaces down to the atomic scale, has been further developed in the last few years to an operative tool, with which atoms and molecules can be manipulated at will at low substrate temperatures in different manners to create and investigate artificial structures, whose properties can be investigated employing spectroscopic dI/dV measurements. The tunnelling current can be used to selectively break chemical bonds, but also to induce chemical association. These possibilities give rise to startling new opportunities for physical and chemical experiments on the single atom and single molecule level. Here we provide a short overview on recent results obtained with these techniques.

Putting to work a molecule able to collect and carry adatoms in a controlled way on a surface is a solution for fabricating atomic structures atom by atom. Investigations have shown that the interaction of an organic molecule with the surface of a metal can induce surface reconstruction down to the atomic scale 1 , 2 , 3 , 4 , 5 . In this way, well-defined nanostructures such as chains of adatoms 2 , atomic trenches 3 , 4 and metal–ligand compounds 5 have been formed. Moreover, the progress in manipulation techniques 6 , 7 , 8 , 9 , 10 induced by a scanning tunnelling microscope (STM) has opened up the possibility of studying artificially built molecular-metal atomic scale structures 11 , 12 , and allowed the atom-by-atom doping of a single C 60 molecule by picking up K atoms 13 . The present work goes a step further and combines STM manipulation techniques with the ability of a molecule to assemble an atomic nanostructure. We present a well-designed six-leg single hexa- t -butyl-hexaphenylbenzene (HB-HPB) molecule 14 , which collects and carries up to six copper adatoms on a Cu(111) surface when manipulated with a STM tip. The ‘HB-HPB-Cu atoms’ complex can be further manipulated, bringing its Cu freight to a predetermined position on the surface where the metal atoms can finally be released.

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 tip-induced manipulation permit these molecules to be brought in contact with a nanoelectrode and the resulting electronic interaction to be analyzed in well controlled conditions. [PUBLICATION ABSTRACT]