Rotation of Ethoxy and Ethyl Moieties on a Molecular Platform on Au(111)

Abstract

Molecular rotors have attracted considerable interest for their prospects in nanotechnology. However, their adsorption on supporting substrates, where they may be addressed individually, usually modifies their properties. Here, we investigate the switching of two closely related three-state rotors mounted on platforms on Au(111) using low-temperature scanning tunneling microscopy and density functional theory calculations. Being physisorbed, the platforms retain important gas-phase properties of the rotor. This simplifies a detailed analysis and permits, for instance, the identification of the vibrational modes involved in the rotation process. The symmetry provided by the platform enables active control of the rotation direction through electrostatic interactions with the tip and charged neighboring adsorbates. The present investigation of two model systems may turn out useful for designing platforms that provide directional rotation and for transferring more sophisticated molecular machines from the gas phase to surfaces.

Addressing a lattice of rotatable molecular dipoles with the electric field of an STM tip

“…Complicating factors include the presence of additional molecules or molecular fragments in the spaces between the equilateral triangles and the presence of the moving tip which does not interact equally with different orientations of the molecules. It has been shown in similar systems recently that charged molecular fragments significantly influence the switching of nearby molecules 11 . In addition, individual molecules that did not switch at all during the series of 153 scans obviously obscure the statistics and more measurements would be necessary for a conclusive analysis.…”

“…Scanning tunnelling microscopy (STM) is an ideally suited surface analysis tool which permits both to characterise and to manipulate objects on the molecular and submolecular scale. This technique is especially appealing in combination with molecular complexes that expose a specific molecular group mounted on a surface-anchored platform [9][10][11] See DOI: 10.1039/cXCP00000x/ ‡ Additional footnotes to the title and authors can be included e.g. 'Present address:' or 'These authors contributed equally to this work' as above using the symbols: ‡, §, and ¶.…”

“…So far, different stimuli have been reported which can induce molecular switching in the junction of an STM. These include the sample voltage , the tunnelling current 11,15,16 , the electric field 10,17 the mechanical presence of the tip [18][19][20] , and photoresponse of the molecule 21,22 . In this work, we fabricated ordered submonolayers of tripodal molecular platforms with a rotatable acetyl group mounted on top.…”

STM induced manipulation of azulene-based molecules and nanostructures: the role of the dipole moment

“…The movement of single molecules on a surface induced by tunneling electrons is presently in the focus of research, especially concerning the excitation mechanisms, 1 the possibility of performing work, 2 and the construction of molecular rotors and motors. [3][4][5] Furthermore, the miniaturization of mechanical components to the atomic limit opens new fundamental scientific questions connected to the way electric energy is converted into movement in molecules. [3][4][5] Scanning tunneling microscopy (STM) at low temperature is a unique tool to investigate single molecules on surfaces and is applied for triggering on-surface chemical reactions, 6 analysing electronic properties, 7 manipulating atoms and molecules, 8 and driving nanocars.…”

“…[3][4][5] Furthermore, the miniaturization of mechanical components to the atomic limit opens new fundamental scientific questions connected to the way electric energy is converted into movement in molecules. [3][4][5] Scanning tunneling microscopy (STM) at low temperature is a unique tool to investigate single molecules on surfaces and is applied for triggering on-surface chemical reactions, 6 analysing electronic properties, 7 manipulating atoms and molecules, 8 and driving nanocars. 1,[9][10][11][12] The influence of electric fields in STM manipulation has been well discussed for several decades.…”