Unidirectional molecular motor on a gold surface (original) (raw)
Related papers
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.
Journal of the American Chemical Society, 2002
Nine new molecular motors, consisting of a 2,3-dihydro-2-methylnaphtho[2,1-b]thiopyran or 2,3dihydro-3-methylphenanthrene upper part and a (thio)xanthene, 10,10-dimethylanthracene, or dibenzocycloheptene lower part, connected by a central double bond, were synthesized. A single stereogenic center, bearing a methyl substituent, is present in each of the motors. MOPAC93-AM1 calculations, NMR studies, and X-ray analysis revealed that these compounds have stable isomers with pseudoaxial orientation of the methyl substituent and less-stable isomers with pseudoequatorial orientation of the methyl substituent. The photochemical and thermal isomerization processes of the motors were studied by NMR and CD spectroscopy. The new molecular motors all show two cis-trans isomerizations upon irradiation, each followed by a thermal helix inversion, resulting in a 360°rotation around the central double bond of the upper part with respect to the lower part. The direction of rotation is controlled by a single stereogenic center created by the methyl substituent at the upper part. The speed of rotation, governed by the two thermal steps, was adjusted to a great extent by structural modifications, with half-lives for the thermal isomerization steps ranging from t1/2 θ 233-0.67 h. The photochemical conversions of two new motors proceeded with near-perfect photoequilibria of 1:99.
Facile assembly of light-driven molecular motors onto a solid surface
Chem. Commun., 2014
In order to improve the rotary motion of surface assembled light-driven molecular motors, tetra-acid-functionalized motors were bound to an amine-coated quartz surface without prior activation of the acid groups. In contrast to earlier bipodal motors, the tetravalent motor showed no significant reduction in the rotation speed when attached to a surface.
Journal of the American Chemical Society, 2006
The introduction of bulky substituents at the stereogenic center of light-driven second-generation molecular motors results in an acceleration of the speed of rotation. This is due to a more strained structure with elongated CdC bonds and a higher energy level of the ground state relative to the transition state for the rate-limiting thermal isomerization step. Understanding the profound influence that variation of the substituent at the stereogenic center holds over the rotational speed of the light-driven molecular motor has enabled the development of the fastest molecular motor reported thus far.
Constructing an Array of Anchored Single-Molecule Rotors on Gold Surfaces
Physical Review Letters, 2008
Molecular rotors with a fixed off-center rotation axis have been observed for single tetra-tert-butyl zinc phthalocyanine molecules on an Au(111) surface by a scanning tunneling microscope at LN 2 temperature. Experiments and first-principles calculations reveal that we introduce gold adatoms at the surface as the stable contact of the molecule to the surface. An off-center rotation axis is formed by a chemical bonding between a nitrogen atom of the molecule and a gold adatom at the surface, which gives them a welldefined contact while the molecules can have rotation-favorable configurations. Furthermore, these singlemolecule rotors self-assemble into large scale ordered arrays on Au(111) surfaces. A fixed rotation axis off center is an important step towards the eventual fabrication of molecular motors or generators.