The Slipping Approach to Self-Assembling [<i>n</i>]Rotaxanes

Asakawa, Masumi; Ashton, Peter R.; Ballardini, Roberto; Balzani, Vincenzo; Bělohradský, Martin; Gandolfi, Maria Teresa; Kocian, Oldrich; Prodi, Luca; Raymo, Françisco M.; Stoddart, J. Fraser; Venturi, Margherita

doi:10.1021/ja961817o

Cited by 148 publications

(103 citation statements)

References 18 publications

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“…As in any structural system, failure will occur at the weakest point. Published reports indicate that this ruptured 74-nN mechanical barrier is considerably weaker than any of the covalent bonds in the system, revealing that the failure occurs as the ring passes over the stopper, a process referred to as ''deslipping'' (24). To our knowledge, all experimental and theoretical data at comparable experimental conditions indicate that the rupture of any covalent bond requires Ͼ1 nN (see Table 2).…”

Section: Resultsmentioning

confidence: 81%

Evaluation of synthetic linear motor-molecule actuation energetics

Brough¹,

Northrop

Schmidt

et al. 2006

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

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By applying atomic force microscope (AFM)-based force spectroscopy together with computational modeling in the form of molecular force-field simulations, we have determined quantitatively the actuation energetics of a synthetic motor-molecule. This multidisciplinary approach was performed on specifically designed, bistable, redox-controllable [2]rotaxanes to probe the steric and electrostatic interactions that dictate their mechanical switching at the single-molecule level. The fusion of experimental force spectroscopy and theoretical computational modeling has revealed that the repulsive electrostatic interaction, which is responsible for the molecular actuation, is as high as 65 kcal⅐mol ؊1 , a result that is supported by ab initio calculations.computational modeling ͉ force spectroscopy ͉ molecular motors ͉ switchable rotaxanes M olecular motors have recently garnered considerable interest within the domains of microsciences and nanosciences (1, 2). Harnessing the ability to selectively, cooperatively, and repeatedly induce structural changes in molecules may hold the promise of engineered systems that operate with the same complexity, elegance, and efficiency as biological motors function in the human body. In natural systems, it has become apparent that both macro and micro processes are initiated and controlled by nanoscale molecular motors (3). For example, myosin and kinesin are associated with muscle contraction and intracellular trafficking, respectively, and have recently found their ways into engineered devices (4, 5). Moreover, initial work has been performed that demonstrates the ability of natural nanoscale molecular motors to power microfabricated systems (6).Synthetic motor-molecules (7-11), which are designed to excel where their biological counterparts fall short, also have been investigated. Whereas devices powered by biological molecules require (4-6) chemical diffusion for actuation stimulus, synthetic molecules have been shown (2, 9) to operate with a variety of different stimuli, thereby lending much greater flexibility to a particular system's design. Moreover, a synthetic nanoscale actuating molecule carries with it an inherent ability to be modified and optimized precisely for a specific task.Switchable, bistable rotaxanes (2, 9), compounds comprised of a dumbbell-shaped component containing two different recognition sites for an encircling ring-shaped component, show particular promise as molecular actuators, given their ability to undergo controllable, reversible mechanical switching with the appropriate chemical, electrochemical, or photochemical stimulus in solution. Toward the goal of device applications, switching has been shown to operate in condensed phases such as in a polymer electrolyte gel (12), on a self-assembled monolayer (SAM) (13), on the solid supports of engineered systems (14), and in molecular switch tunnel junctions (15). Bistable rotaxanes benefit from their synthesis being highly modular, a virtue that allows for a considerable degree of flexibility in their des...

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Section: Resultsmentioning

confidence: 81%

Evaluation of synthetic linear motor-molecule actuation energetics

Brough¹,

Northrop

Schmidt

et al. 2006

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

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“…The so-called slippage approach has been employed successfully, in the past three decades to self-assemble a series of linear [135][136][137][138][139] and branched [n]rotaxanes [140][141][142] under thermodynamic control. In this strategy, the macrocycle and the dumbbell, which are synthesized independently prior to self-assembly, are usually heated together in an appropriate solvent until the macrocycle slips over the dumbbell's stopper by overcoming the associated free energy of activation.…”

Section: Synthesis Of Interlocked Molecules By Slippagementioning

confidence: 99%

“…Recently, the Stoddart group has demonstrated [135][136] the efficiency of the slippage approach by self-assembling a number of linear and branched [2]-, [3]-, and [4]rotaxanes, incorporating p-electron-rich hydroquinone-based macrocyclic polyethers and p-electron-deficient bipyridinium-based dumbbellshaped compounds.A kinetic investigation of the slippage process revealed [138,145] that the free energies of activation associated with the slipping-on and slipping-off processes are correlated with the size of the cavity of the macrocyclic component, as well as with the size of the stoppers attached to the dumbbellshaped component. The free energy of activation was observed to increase upon reducing the size of the cavity of the macrocycle and/or enlarging the bulk of the stoppers.…”

Section: Synthesis Of Interlocked Molecules By Slippagementioning

confidence: 99%

“…This approach has led to the preparation of rotaxanes by either threading-followedby-stoppering [152,[182][183][184] or slippage [135][136][137][138][139][140][141][142][143][144][145][146][147][148] protocols. However, in 2001, the Stoddart group [185] reported a simple and highly effective dynamic procedure (Scheme 10) for the formation of a [2]rotaxane by the clipping of a diamine with a dialdehyde, as the precursor components of a [24]crown-8-like macrocycle, around a dialkylammonium center that also acts as a template.…”

Section: Ammonium Ion Templated Synthesesmentioning

confidence: 99%

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Templated Synthesis of Interlocked Molecules

Aricò

Badjić

Cantrill

et al. 2005

Topics in Current Chemistry

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“…[9] Subsequent kinetic studies revealed that the size of both the macrocycle and stoppers of the axle affect the rates of slippage. [9][10][11] A number of groups have since exploited slippage to synthesise rotaxanes. [12] One of the inherent problems of rotaxane synthesis by using the slippage strategy, however, is the question of whether the resulting slippage species is a true rotaxane or a pseudorotaxane with some rotaxane character; rotaxanes are kinetically stable, whereas pseudorotaxanes can dissociate into the macrocycle and axle components, for example when dissolved in polar solvents.…”

Section: Introductionmentioning

confidence: 99%

Kinetic Studies Exploring the Role of Anion Templation in the Slippage Formation of Rotaxane‐Like Structures

McConnell

Beer

2011

Chemistry A European J

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The first examples of the slippage formation of rotaxane-like structures in the presence of an anion template are reported between a macrocycle, synthesised by exploiting Eglinton coupling, and stoppered pyridinium axle components. The role of the anion template in the slippage process has been explored by kinetic studies. (1)H NMR spectroscopic investigations reveal the slippage species formed are not rotaxanes but pseudorotaxanes with some rotaxane character. The anion template significantly influences the amount of rotaxane character and the rate of slippage. Importantly, the fastest slippage rates, k(on), are achieved with the non-coordinating hexafluorophosphate anion, whereas the slowest slippage off rates, k(off), are observed in the presence of coordinating anions, such as chloride. Since the k(off) rates are significantly smaller than the k(on) rates in the presence of coordinating anions, these anions act as templates favouring formation of the slippage species thermodynamically. Consequently, the resulting pseudorotaxanes with coordinating anions have greater rotaxane character. Two strategies for converting the slippage pseudorotaxanes into rotaxanes using hydrogenation or complexation with cobalt carbonyl are investigated.

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The Slipping Approach to Self-Assembling [n]Rotaxanes

Cited by 148 publications

References 18 publications

Evaluation of synthetic linear motor-molecule actuation energetics

Evaluation of synthetic linear motor-molecule actuation energetics

Templated Synthesis of Interlocked Molecules

Kinetic Studies Exploring the Role of Anion Templation in the Slippage Formation of Rotaxane‐Like Structures

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