Synthetic Molecular Machines

Kay, Euan R.; Leigh, David A.

doi:10.1002/352760572x.ch7

Cited by 23 publications

(7 citation statements)

References 59 publications

(82 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Indeed, they do this so effectively that they can be capable of transporting objects many times more massive than themselves 2 and have even been used to power prototypical hybrid mechanical devices [3][4][5][6][7][8] . However, performing well-defined mechanical tasks and measurable work with synthetic molecular systems that bias brownian motion has proved much more elusive [9][10][11][12][13] . Here we report on the macroscopic (millimetre-scale) directional transport of a droplet on a photo-responsive surface created by using the nanometre displacement of the components of light-switchable molecular shuttles to expose or conceal fluoroalkane residues and thereby modify the surface properties.…”

mentioning

confidence: 99%

“…Stimuli-responsive molecular shuttles are rotaxanes in which the macrocycle is translocated from one position ('station') on the thread to a second site through biased brownian motion in response to an external trigger (for example, light, electrons, temperature, pH, nature of the environment, reversible covalent bond formation, and so on) [9][10][11][12][13][14][15][16][17][18][19][20] . These systems are viewed as potential elements for molecular machinery and the change in position of the subunits has been used as a nanoscale mechanical switch to vary physical properties such as conductivity 14 , induced circular dichroism 15 and fluorescence [16][17][18][19] .…”

mentioning

confidence: 99%

See 1 more Smart Citation

Macroscopic transport by synthetic molecular machines

et al. 2005

Self Cite

View full text Add to dashboard Cite

Nature uses molecular motors and machines in virtually every significant biological process, but demonstrating that simpler artificial structures operating through the same gross mechanisms can be interfaced with-and perform physical tasks in-the macroscopic world represents a significant hurdle for molecular nanotechnology. Here we describe a wholly synthetic molecular system that converts an external energy source (light) into biased brownian motion to transport a macroscopic cargo and do measurable work. The millimetre-scale directional transport of a liquid on a surface is achieved by using the biased brownian motion of stimuli-responsive rotaxanes ('molecular shuttles') to expose or conceal fluoroalkane residues and thereby modify surface tension. The collective operation of a monolayer of the molecular shuttles is sufficient to power the movement of a microlitre droplet of diiodomethane up a twelve-degree incline.

show abstract

mentioning

confidence: 99%

mentioning

confidence: 99%

Macroscopic transport by synthetic molecular machines

et al. 2005

Self Cite

View full text Add to dashboard Cite

show abstract

“…I t has recently become possible to synthesize molecules that function like mechanical devices (1)(2)(3)(4), such as switches (5-7), motors (8)(9)(10)(11), brakes (12), turnstiles (13), and elevators (14). These manmade molecular machines can be considered as nanoscale versions of their macroscopic analogues.…”

mentioning

confidence: 99%

Probing the structure of a rotaxane with two-dimensional infrared spectroscopy

Larsen

Bodis

Buma

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

View full text Add to dashboard Cite

Femtosecond 2D-IR spectroscopy has been used to study the structure of a [2]rotaxane composed of a benzylic amide macrocycle that is mechanically interlocked onto a succinamide-based thread. Both the macrocycle and the thread contain carbonyl groups, and by determining the coupling between the stretching modes of these groups from the cross-peaks in the 2D-IR spectrum, the structure of the macrocycle-thread system has been probed. Our results demonstrate that 2D-IR spectroscopy can be used to observe structural changes in molecular devices on a picosecond time scale.femtosecond IR spectroscopy ͉ molecular machines I t has recently become possible to synthesize molecules that function like mechanical devices (1-4), such as switches (5-7), motors (8-11), brakes (12), turnstiles (13), and elevators (14). These manmade molecular machines can be considered as nanoscale versions of their macroscopic analogues. However, many well known macroscopic concepts no longer apply at a molecular level. For instance, the concept of viscous friction becomes meaningless as the size of moving object approaches that of the molecules of the surrounding medium and as the time scale of the motion approaches that of the molecules of this medium (15). This regime of device operation is a new one, where the elementary component motions (rotations around covalent bonds and the making and breaking of hydrogen bonds) and the fluctuations of the surroundings both take place on the picosecond or subpicosecond time scale. Hence, for a detailed understanding of the physics and chemistry of molecular devices, experiments that probe their motion on an ultrafast time scale are essential, and the insights obtained from such experiments should be important for potential applications.A promising technique for such experiments is 2D-IR spectroscopy. With 2D-IR spectroscopy, molecular conformations are determined by measuring couplings between molecular vibrations. The method was inspired by multidimensional NMR spectroscopy, in which couplings between nuclear spins are used for structure resolution (16). Like nuclear spins, normal modes are often well localized in the molecule (especially when they involve stretching of specific chemical bonds), and the coupling between them is mainly dipolar. The 2D-IR spectrum can therefore give direct access to the conformation of a molecule or its parts (17-23). The important advantage of 2D-IR spectroscopy as compared with 2D-NMR spectroscopy is its time resolution: The conformation can be determined with a time resolution determined by the free-induction decay of the transition, which is generally Ͻ1 ps. As a consequence, 2D-IR spectroscopy can be used to study motion in molecular systems on a time scale comparable to that of the elementary molecular motions. To this purpose, one triggers the motion (typically with a short optical pulse) and monitors the subsequent structural changes by recording 2D-IR spectra at different time delays with respect to the external trigger. In this way, a ''movie'' of the molecular...

show abstract

“…Molecular systems that respond to an external stimulus (electrical, chemical, optical, mechanical, or environmental) and modify their geometry accordingly are potentially interesting as nano actuators, building blocks for mechanical molecular machines, and potential memories and sensors . Rotaxanes form a class of molecular architectures with adaptive functionality .…”

Section: Introductionmentioning

confidence: 99%

Self-organization of Rotaxane Thin Films into Spatially Correlated Nanostructures: Morphological and Structural Aspects

et al. 2005

Self Cite

View full text Add to dashboard Cite

The self-organization of rotaxane thin films into spatially correlated nanostructures is shown to occur upon a thermal stimulus. The mechanism of formation of nanostructures and their organization has been investigated using atomic force microscopy, bright field transmission electron microscopy, selected area electron diffraction, and molecular mechanics simulations. The evolution of the nanostructures follows a complex pathway, where a rotaxane thin film first dewets from the substrate to form nanosized droplets. Droplets coalesce by ripening, generating spatially correlated motifs. In a later stage, the larger droplets change shape, nucleate, and coalesce to yield crystallites that grow into larger crystals by incorporating the surrounding droplets. The results show the following: (i) the nanostructures represent a metastable state of a crystallization process; (ii) spatial correlations emerge during ripening, but they are destroyed as stable nuclei are formed and crystallization proceeds to completion; iii) crystallization, either on graphite or amorphous carbon films, leads to a precise basal plane, viz. (010), which has minimum surface energy. The inherent degrees of freedom permitted in the rotaxane architecture favors the re-organization and nucleation of the film in the solid state. Low-energy trajectories leading to crystallites with stable surfaces and minimum energy contact plane are found to occur via concerted, small amplitude, internal motions without disruption of packing and intermolecular contacts.

show abstract

Synthetic Molecular Machines

Cited by 23 publications

References 59 publications

Macroscopic transport by synthetic molecular machines

Macroscopic transport by synthetic molecular machines

Probing the structure of a rotaxane with two-dimensional infrared spectroscopy

Self-organization of Rotaxane Thin Films into Spatially Correlated Nanostructures: Morphological and Structural Aspects

Contact Info

Product

Resources

About