Electrochemically Switchable Hydrogen-Bonded Molecular Shuttles

Altieri, Alessio; Gatti, Francesco G.; Kay, Euan R.; Leigh, David A.; Martel, David; Paolucci, Francesco; Slawin, Alexandra M. Z.; Wong, Jenny K. Y.

doi:10.1021/ja0352552

Cited by 235 publications

(180 citation statements)

References 26 publications

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“…From x-ray studies, 23 we find the size of the [2]rotaxane to be ∼2 nm. Assuming a spherical shape with the Stokes radius of 1 nm, we estimate the orientational relaxation time to be ∼400 ps.…”

Section: B Population Relaxation and Resonant Vibrational Energy Tramentioning

confidence: 93%

“…In addition, the incorporation of these aliphatic stoppers improves the solubility of the interlocked molecule in halogenated solvents in comparison to previously investigated rotaxanes with aromatic stoppers. 23,31 All experiments are performed at room temperature on 10 mM solution of the [2]rotaxane in CDCl 3 kept between two CaF 2 windows using a 1 mm thick spacer.…”

Section: Methodsmentioning

confidence: 99%

“…21,22 Here we employ this technique to investigate the ultrafast intercomponent fluctuations in a [2]rotaxane consisting of a succinamide-based thread and a benzylic-amide-based macrocycle. 4,15,17,23 The experiments reveal that mechanical bonding in a rotaxane has little effect on the amplitude or rate of (sub)picosecond fluctuations of the intercomponent hydrogen bonds, but that it decreases the rate of spontaneous breaking and remaking of these hydrogen bonds by more than an order of magnitude.…”

Section: Introductionmentioning

confidence: 99%

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Bimodal dynamics of mechanically constrained hydrogen bonds revealed by vibrational photon echoes

Bodis

Yeremenko

Berná

et al. 2011

The Journal of Chemical Physics

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Bimodal dynamics of mechanically constrained hydrogen bonds revealed by vibrational photon echoes Bodis, P.; Yeremenko, S.; Berna, J.; Buma, W.J.; Leigh, D.A.; Woutersen, S. General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. We have investigated the dynamics of the hydrogen bonds that connect the components of a [2]rotaxane in solution. In this rotaxane, the amide groups in the benzylic-amide macrocycle and the succinamide thread are connected by four equivalent N−H· · ·O=C hydrogen bonds. The fluctuations of these hydrogen bonds are mirrored by the frequency fluctuations of the NH-stretch modes, which are probed by means of three-pulse photon-echo peak shift spectroscopy. The hydrogen-bond fluctuations occur on three different time scales, with time constants of 0.1, 0.6, and ≥200 ps. Comparing these three time scales to the ones found in liquid formamide, which contains the same hydrogenbonded amide motif but without mechanical constraints, we find that the faster two components, which are associated with small-amplitude fluctuations in the strength of the N−H· · ·O=C hydrogen bonds, are very similar in the liquid and the rotaxane. However, the third component, which is associated with the breaking and subsequent reformation of hydrogen bonds, is found to be much slower in the rotaxane than in the liquid. It can be concluded that the mechanical bonding in a rotaxane does not influence the amplitude and time scale of the small-amplitude fluctuations of the hydrogen bonds, but strongly slows down the complete dissociation of these hydrogen bonds. This is probably because in a rotaxane breaking of the macrocycle-axle contacts is severely hindered by the mechanical constraints. The hydrogen-bond dynamics in rotaxane-based molecular machines can therefore be regarded as liquidlike on a time scale 1 ps and less, but structurally frozen on longer (up to at least 200 ps) time scales.

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Section: B Population Relaxation and Resonant Vibrational Energy Tramentioning

confidence: 93%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Bimodal dynamics of mechanically constrained hydrogen bonds revealed by vibrational photon echoes

Bodis

Yeremenko

Berná

et al. 2011

The Journal of Chemical Physics

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“…The [2]rotaxane was synthesized by following the procedure described in ref. 6. The experiments are carried out at room temperature on 2.5 mM solutions of the rotaxane in CHCl 3 kept between two CaF 2 windows separated by a 1-mm Teflon spacer.…”

Section: Methodsmentioning

confidence: 99%

“…We have chosen the [2]rotaxane shown in Fig. 1, which is composed of a benzylic amide macrocycle that is mechanically interlocked onto a succinamide-based thread and held in position by a network of hydrogen bonds (6). This rotaxane is representative of a large class of rotaxane-and catenane-based devices that includes molecular shuttles (5) and motors (10,11).…”

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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.

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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...

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Monofunctionally trans ‐Diammine Platinum( II )‐Modified Peptide Nucleic Acid Oligomers: A New Generation of Potential Antisense Drugs

Schmidt

Boudvillain

Schwartz

et al. 2002

Chemistry A European J

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Rotaxane molecular shuttles were studied in which a tetralactam macrocyclic ring moves between a succinamide station and a second station in which the structure is varied. Station 2 in all cases is an aromatic imide, which is a poor hydrogen‐bond acceptor in the neutral form, but a strong one when reduced with one or two electrons. When the charge density on the hydrogen‐bond‐accepting carbonyl groups in station 2 is reduced by changing a naphthalimide into a naphthalene diimide radical anion, the shuttling rate changes only slightly. When station 2 is a pyromellitimide radical anion, however, the shuttling rate is significantly reduced. This implies that the shuttling rate is not only determined by the initial unbinding of the ring from the first station, as previously supposed. An alternative reaction mechanism is proposed in which the ring binds to both stations in the transition state.

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Electrochemically Switchable Hydrogen-Bonded Molecular Shuttles

Cited by 235 publications

References 26 publications

Bimodal dynamics of mechanically constrained hydrogen bonds revealed by vibrational photon echoes

Bimodal dynamics of mechanically constrained hydrogen bonds revealed by vibrational photon echoes

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

Monofunctionally trans ‐Diammine Platinum( II )‐Modified Peptide Nucleic Acid Oligomers: A New Generation of Potential Antisense Drugs

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