Current-Driven Supramolecular Motor with In Situ Surface Chiral Directionality Switching (original) (raw)
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Supramolecular Rotor and Translator at Work: On-Surface Movement of Single Atoms
ACS Nano, 2015
A supramolecular nanostructure composed of four 4-acetylbiphenyl molecules and self-assembled on Au (111) was loaded with single Au adatoms and studied by scanning tunneling microscopy at low temperature. By applying voltage pulses to the supramolecular structure, the loaded Au atoms can be rotated and translated in a controlled manner. The manipulation of the gold adatoms is driven neither by mechanical interaction nor by direct electronic excitation. At the electronic resonance and driven by the tunneling current intensity, the supramolecular nanostructure performs a small amount of work of about 8 Â 10 À21 J, while transporting the single Au atom from one adsorption site to the next. Using the measured average excitation time necessary to induce the movement, we determine the mechanical motive power of the device, yielding about 3 Â 10 À21 W.
A chiral molecular propeller designed for unidirectional rotations on a surface
Nature Communications, 2019
Synthetic molecular machines designed to operate on materials surfaces can convert energy into motion and they may be useful to incorporate into solid state devices. Here, we develop and characterize a multi-component molecular propeller that enables unidirectional rotations on a material surface when energized. Our propeller is composed of a rotator with three molecular blades linked via a ruthenium atom to a ratchet-shaped molecular gear. Upon adsorption on a gold crystal surface, the two dimensional nature of the surface breaks the symmetry and left or right tilting of the molecular gear-teeth induces chirality. The molecular gear dictates the rotational direction of the propellers and step-wise rotations can be induced by applying an electric field or using inelastic tunneling electrons from a scanning tunneling microscope tip. By means of scanning tunneling microscope manipulation and imaging, the rotation steps of individual molecular propellers are directly visualized, which confirms the unidirectional rotations of both left and right handed molecular propellers into clockwise and anticlockwise directions respectively.
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.
A Chemically Switchable Molecular Pinwheel
Angewandte Chemie International Edition, 2006
The bottom-up fabrication of nanoscopic devices such as gears, [1] ratchets, [2] turnstiles, [3] switches, [4] and elevators [5] continues to attract much attention. The interest in molecular rotors in solution, [6] inside crystals, [7-9] and in the gas phase [10] has recently been extended to surface-mounted rotors; [11-13] most recently, a light-driven molecular rotor anchored to a gold surface has been demonstrated, [13] and a recent comprehensive review of artificial molecular rotors is available. [14] Derivatized porphyrins are versatile building blocks for the creation of many different types of assemblies, including supramolecular structures. [15] When adsorbed on surfaces, they can be imaged with scanning tunneling microscopy (STM). Copper tetra-(3,5-di-tert-butylphenyl)porphyrin (Cu-TBPP) adsorbed on Cu(100) was the first case in which singlemolecule manipulation at room temperature [16] and conformational recognition were achieved by means of STM. [17] In subsequent work with Cu-TBPP, Moresco et al. [18] were able to observe tip-induced conformational changes in individual di-tert-butyl phenyl (tBP) groups through height changes in the STM images. More recently, a metal-free TBPP functionalized with cyanophenyl terminal groups and adsorbed on Au(111) was used to form molecular assemblies including tetramers and one-dimensional wires; the structures of these assemblies were controlled by purposeful synthetic design of the monomer molecule. [19] Photoexcited molecular rotors have been observed in solution, [20] and the rotation of individual adsorbed molecules has been induced by manipulation with an STM tip; [11] however, reports of surfacemounted rotors are extremely sparse. [14] We describe herein a self-assembly method for switching on the rotation of adsorbed porphyrin molecules by mounting them on an appropriately functionalized ligand, one end of which binds to the surface, the other to the "hub" of the porphyrin. This was achieved by using zinc tetra-(3,5-di-tert-butylphenyl)porphyrin [21] (Zn-TBPP; Scheme 1 a), whose structure is such that interaction between the macrocycle component and the Ag(100) surface is minimized. As a result of steric repulsion, [*] O.
Controlled Rotary Motion in a Monolayer of Molecular Motors
Angewandte Chemie International Edition, 2007
Rotary molecular motors are ubiquitous in natural systems where they are used for diverse tasks including molecular transport, cellular translocation, and ATP synthesis, and are considered key components of future synthetic nanomechanical devices. In many of these systems, such as ATPase or the bacterial flagella motor, immobilization into the cellular membrane allows their rotary action to be harnessed. Attaching biological or synthetic molecular rotary motors to solid substrates is considered to be a key step toward the fabrication of devices that exploit the collective rotational mechanical motion generated by these systems. Although linear synthetic and biological motors have been mounted on surfaces, examples of surface-bound rotary motors are scarce. Preliminary work to this end includes the successful characterization of functioning ATPase while immobilized on quartz and recently, a single example of synthetic rotary molecular motors functioning on gold nanoparticles in solution. Although the latter is a significant step toward future applications, the nanoparticles in solution are still overwhelmed by Brownian rotation and translation, and the motor function might to some extent suffer from excitedstate quenching by the gold, making it difficult to harness work from the system.
Chemical Communications, 2011
Supplementary Information 1D and 2D NMR experiments were recorded at 500 MHz on a Varian 500. Proton peak positions were referenced to the peak of residual non deuterated solvent (set at δ 7.26 for CDCl 3 , and δ 5.33 for CD 2 Cl 2). UV-vis absorption spectra were recorded with a Jasco V-570 UV/Vis/NIR spectrophotometer. Emission spectra were taken on a Spex Fluoromax-2 spectrofluorimeter, equipped with Hamamatsu R3896 tubes. Solvents for spectroscopic measurements were of spectroscopic grade, all the other solvents were of reagent grade quality, and used as received. CDCl 3 , used in NMR experiments, was treated with basic alumina prior to use.
Langmuir : the ACS journal of surfaces and colloids, 2018
We combine ambient (air) and ultrahigh vacuum (UHV) scanning tunneling microscopy (STM) and spectroscopy (STS) investigations together with density functional theory (DFT) calculations to gain a subnanometer insight into the structure and dynamic of two-dimensional (2D) surface-supported molecular networks. The planar tetraferrocene-porphyrin molecules employed in this study undergo spontaneous self-assembly via the formation of hydrogen bonded networks at the gold substrate-solution interface. To mimic liquid phase ambient deposition conditions, film formation was accomplished in UHV by electro-spraying a solution of the molecule in chloroform onto an Au(111) substrate, thereby providing access to the full spectroscopic capabilities of STM that can be hardly attained under ambient conditions. We show that molecular assembly on Au (111) is identical in films prepared under the two different conditions, and in good agreement with the theoretical predictions. However, we observe the c...