A rack-and-pinion device at the molecular scale

Abstract

Molecular machines, and in particular molecular motors with synthetic molecular structures and fuelled by external light, voltage or chemical conversions, have recently been reported. 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). 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 or indirect signatures 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.

Low-level light therapy of the eye and brain

“…In the case of chromophore-containing enzymes, this allows a very efficient coupling of electromagnetic free energy flow to the chemical energy flow of substrate conversion. 14,15 As discussed below, it is a remarkable finding that in mammalian tissues, the photosensitivity of certain chromophores conserves physiologic significance, in spite of their adaptation to naturally function without external photons. 16 A distinctive property of chromophores is that they absorb particular wavelengths and reflect others, thus conferring specific colors to molecules.…”

Synthesis and Characterization of a Series of Ruthenium Tris(β‐diketonato) Complexes by an UHV‐STM Investigation and Numerical Calculations

“…This is the reason for choosing the dibenzoylmethanato (dbm) ligand, mainly because of its propensity to adhere to the substrate as a result of its phenyl rings. [45,46] In this work, we report on the synthesis and characterization of a series of mononuclear ruthenium complexes with dbm ligands and functionalized or non-functionalized acac ligands. We also present a study of the adsorption of a ruthenium tris(β-diketonate) complex at low temperature, i.e.…”

Constructing an Array of Anchored Single-Molecule Rotors on Gold Surfaces

“…In addition, the studies mainly focused on single molecules, while it is desirable, for eventual applications, that individual molecular rotors self-assemble into large scale ordered arrays while keeping their original functions. Here we show, using scanning tunneling microscopy (STM) [7][8][9][10][11][12], that single tetratert-butyl zinc phthalocyanine (ðt-BuÞ 4 -ZnPc) molecules on the reconstructed Au(111) surface possess a welldefined rotation axis fixed on the surface, and also, that these single-molecule rotors form large scale ordered arrays due to the reconstruction of the gold surface.Our experiments were conducted with an Omicron MBE-LTSTM system with a base pressure below 3:0 Â 10 À10 mbar. An atomically clean Au(111) surface was prepared by repeated cycles of Ar þ sputtering and subsequent annealing, and then dosed with a minute quantity of ðt-BuÞ 4 -ZnPc molecules.…”

“…For molecular rotors [6] a high level of control over the rotation axis and, equivalently, selfassembly on a very large scale, are the key ingredients for their integration into complex molecular machines. Previously, the reported molecular rotors on surfaces had no fixed axis on the surface [7][8][9][10]. In addition, the studies mainly focused on single molecules, while it is desirable, for eventual applications, that individual molecular rotors self-assemble into large scale ordered arrays while keeping their original functions.…”