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Volumn , Issue , 2005, Pages 333-406

Synthetic Molecular Machines

Author keywords

Controlling configurational changes; Controlling conformational changes; Controlling motion in interlocked systems; Controlling motion in supramolecular systems; Functional synthetic receptors; Synthetic molecular machines; Useful molecular machines

Indexed keywords


EID: 26444602299     PISSN: None     EISSN: None     Source Type: Book    
DOI: 10.1002/352760572X.ch7     Document Type: Chapter
Times cited : (23)

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    • There are some examples of catenanes and rotaxanes constructed under thermody-namic control using dynamic processes such as olefin metathesis or imine bond formation (see for example:, and references therein). Such systems cannot act as molecular machines if they exchange components with the bulk quicker than the timescale of their stimuli-induced motion.
    • There are some examples of catenanes and rotaxanes constructed under thermody-namic control using dynamic processes such as olefin metathesis or imine bond formation (see for example: J. S. Hannam, T. J. Kidd, D. A. Leigh, A. J. Wilson, Org. Lett. 2003, 5, 1907-1910 and references therein). Such systems cannot act as molecular machines if they exchange components with the bulk quicker than the timescale of their stimuli-induced motion.
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    • Another synthetic strategy, 'slippage', theoretically provides a route to rotaxanes under thermodynamic control. However, the chemical assemblies thus far prepared by this route are misclassified in the literature. They do not satisfy the structural requirements of a rotaxane since the components can be separated from each other without breaking covalent bonds. Rather they are pseudo-rotaxanes-threaded host-guest complexes which are kinetical-ly stable at room temperature. This incorrect classification is not normally an issue because the physical behavior of kinetically stable pseudo-rotaxanes generally mirrors that of rotaxanes. However, it increasingly appears to be confusing non-specialists into thinking that rotaxanes are supramolec-ular species or that pseudo-rotaxanes that are not kinetically stable can act as molecular machines. Slippage could be used as a strategy to form rotaxanes if the stabilization gained from the ring binding on the thread was sufficient to mean that.
    • Another synthetic strategy, 'slippage', theoretically provides a route to rotaxanes under thermodynamic control. However, the chemical assemblies thus far prepared by this route are misclassified in the literature. They do not satisfy the structural requirements of a rotaxane since the components can be separated from each other without breaking covalent bonds. Rather they are pseudo-rotaxanes-threaded host-guest complexes which are kinetical-ly stable at room temperature. This incorrect classification is not normally an issue because the physical behavior of kinetically stable pseudo-rotaxanes generally mirrors that of rotaxanes. However, it increasingly appears to be confusing non-specialists into thinking that rotaxanes are supramolec-ular species or that pseudo-rotaxanes that are not kinetically stable can act as molecular machines. Slippage could be used as a strategy to form rotaxanes if the stabilization gained from the ring binding on the thread was sufficient to mean that covalent bond breaking is less energetically demanding than de-threading of the rings over the stoppers. To date no structures of this type have been reported.
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    • For reviews on the development of interlocked molecules as molecular machines, see refs. [6a, 6c, 6e] and:
    • For reviews on the development of interlocked molecules as molecular machines, see refs. [6a, 6c, 6e] and: V. Balzani, M. Gomez-Lopez, J. F. Stoddart, Acc. Chem. Res. 1998, 31, 405-414;
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    • Numbers in square brackets preceding the names of interlocked compounds indicate the number of mechanically interlocked species, e.g. a [2]rotaxane consists of one macrocycle and one thread component mechanically interlocked; two macrocycles both locked around the same thread would constitute a [3]rotaxane.
    • Numbers in square brackets preceding the names of interlocked compounds indicate the number of mechanically interlocked species, e.g. a [2]rotaxane consists of one macrocycle and one thread component mechanically interlocked; two macrocycles both locked around the same thread would constitute a [3]rotaxane.
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    • The concept of constructing a molecular catenane was first postulated by Willstät-ters before 1912 (see refs. [59a, 59b]). The first statistical synthesis of a catenane was achieved by Wasserman in 1960:
    • The concept of constructing a molecular catenane was first postulated by Willstät-ters before 1912 (see refs. [59a, 59b]). The first statistical synthesis of a catenane was achieved by Wasserman in 1960: E. Wasserman, J. Am. Chem. Soc. 1960, 82, 4433-4434;
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    • and the first directed synthesis by Lüttringhaus and Schill in 1964:
    • and the first directed synthesis by Lüttringhaus and Schill in 1964: G. Schill, A. Lüttringhaus, Angew. Chem. Int. Ed. Engl. 1964, 3, 546-547.
    • (1964) Angew. Chem. Int. Ed. Engl. , vol.3 , pp. 546-547
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    • The first rotaxane was synthesized by Harrison and Harrison in 1967:
    • The first rotaxane was synthesized by Harrison and Harrison in 1967: I. T. Harrison, S. Harrison, J. Am. Chem. Soc. 1967, 89, 5723-5724;
    • (1967) J. Am. Chem. Soc. , vol.89 , pp. 5723-5724
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    • Metal-coordinated catenanes are sometimes known as catenates. Demetallation to give the uncomplexed, but still interlocked, ligands gives a catenand. No similar nomenclature is used for metal-coordinated rotaxane-like structures however, which are named as their organic counterparts. In recent times, the use of the terms "catenate" and "catenand" has largely been superseded in the literature by the more general "catenane".
    • Metal-coordinated catenanes are sometimes known as catenates. Demetallation to give the uncomplexed, but still interlocked, ligands gives a catenand. No similar nomenclature is used for metal-coordinated rotaxane-like structures however, which are named as their organic counterparts. In recent times, the use of the terms "catenate" and "catenand" has largely been superseded in the literature by the more general "catenane".
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    • This previously inaccessible species was obtained by trapping round an acyclic, stoppered benzylic amide thread to create a [2]rotaxane, followed by controlled cleavage of the thread and resultant de-threading:
    • This previously inaccessible species was obtained by trapping round an acyclic, stoppered benzylic amide thread to create a [2]rotaxane, followed by controlled cleavage of the thread and resultant de-threading: A. G. Johnston, D. A. Leigh, A. Murphy, J. P. Smart, M. D. Deegan, J. Am. Chem. Soc. 1996, 118, 10662-10663.
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    • The distal isomer may still be involved transiently in the circumvolution mechanism.
    • The distal isomer may still be involved transiently in the circumvolution mechanism.
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    • With the notable exception of the earliest statistically constructed [2]rotaxanes (see refs. [64c, 64d]), there are very few examples of rotaxanes without any recognition elements in the thread, see however:
    • With the notable exception of the earliest statistically constructed [2]rotaxanes (see refs. [64c, 64d]), there are very few examples of rotaxanes without any recognition elements in the thread, see however: C. Heim, A. Affeld, M. Nieger, F. Vögtle, Helv. Chim. Acta 1999, 82, 746-759;
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    • Even in 1991, when reporting the first degenerate molecular shuttle (see ref. [88]), Stoddart noted that: "The opportunity now exists to desymmetrize the molecular shuttle by inserting nonidentical 'stations' along the polyether 'thread' in such a manner that these different 'stations' can be addressed selectively by chemical, electrochemical, or photochemical means and so provide a mechanism to drive the 'bead' to and fro between 'stations' along the 'thread'.
    • Even in 1991, when reporting the first degenerate molecular shuttle (see ref. [88]), Stoddart noted that: "The opportunity now exists to desymmetrize the molecular shuttle by inserting nonidentical 'stations' along the polyether 'thread' in such a manner that these different 'stations' can be addressed selectively by chemical, electrochemical, or photochemical means and so provide a mechanism to drive the 'bead' to and fro between 'stations' along the 'thread'.
  • 214
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    • As long as the chemical reaction is fast with respect to the movement of the macrocycle.
    • As long as the chemical reaction is fast with respect to the movement of the macrocycle.
  • 221
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    • For an example of another pH switched shuttle from the Stoddart group, see
    • For an example of another pH switched shuttle from the Stoddart group, see: A. M. Elizarov, S.-H. Chiu, J. F. Stoddart, J. Org. Chem. 2002, 67, 9175-9181.
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    • Elizarov, A.M.1    Chiu, S.-H.2    Stoddart, J.F.3
  • 229
    • 84890971808 scopus 로고    scopus 로고
    • Shuttle 41 also shows a certain degree of electrochemical switching in the deproto-nated state when electrochemical reduction of the bipyridinium unit causes movement of the macrocycle back towards the amine moiety. In this state however, the electron-rich macrocycle has no significant favorable interactions with the thread and its position is not well-defined, see ref. [99a].
    • Shuttle 41 also shows a certain degree of electrochemical switching in the deproto-nated state when electrochemical reduction of the bipyridinium unit causes movement of the macrocycle back towards the amine moiety. In this state however, the electron-rich macrocycle has no significant favorable interactions with the thread and its position is not well-defined, see ref. [99a].
  • 237
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    • Heat has been used to effect cis-trans isomerization in 46 resulting in a concomitant net change of position of the ring (see ref. [108]), while a temperature increase has also been used to overcome a significant kinetic barrier to shuttling, following a chemical change in a kineti-cally stable pseudorotaxane (see Ref. [58b]). In neither of these cases is the process reversible on cooling the material without some other stimulus being applied.
    • Heat has been used to effect cis-trans isomerization in 46 resulting in a concomitant net change of position of the ring (see ref. [108]), while a temperature increase has also been used to overcome a significant kinetic barrier to shuttling, following a chemical change in a kineti-cally stable pseudorotaxane (see Ref. [58b]). In neither of these cases is the process reversible on cooling the material without some other stimulus being applied.
  • 238
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    • 12) possible C-C rotamers and a significant number of these degrees of freedom must be lost upon forming the dodec-Z-47 structure.
    • 12) possible C-C rotamers and a significant number of these degrees of freedom must be lost upon forming the dodec-Z-47 structure.
  • 239
    • 0037071733 scopus 로고    scopus 로고
    • A series of theoretical designs for entropy-driven mechanical motion in mechanically interlocked molecules have been suggested, see
    • A series of theoretical designs for entropy-driven mechanical motion in mechanically interlocked molecules have been suggested, see: A. Hanke, R. Metzler, Chem. Phys. Lett. 2002, 359, 22-26.
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    • Hanke, A.1    Metzler, R.2
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    • 84891007596 scopus 로고    scopus 로고
    • The use of terms such as "all or nothing" or "quantitative" are inappropriate descriptions of an equilibrium.
    • The use of terms such as "all or nothing" or "quantitative" are inappropriate descriptions of an equilibrium.
  • 243
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    • For examples where the ring in a rotax-ane is pirouetted between two distinct orientations, using the same principles as molecular shuttling (Section 7.5.5), see:
    • For examples where the ring in a rotax-ane is pirouetted between two distinct orientations, using the same principles as molecular shuttling (Section 7.5.5), see: L. Raehm, J.-M. Kern, J.-P. Sauvage, Chem. Eur. J. 1999, 5, 3310-3317;
    • (1999) Chem. Eur. J. , vol.5 , pp. 3310-3317
    • Raehm, L.1    Kern, J.-M.2    Sauvage, J.-P.3
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    • It has recently been suggested that unidirectional pirouetting could result from simply derivatizing rotaxanes with chiral or knotted stoppers (see:, As discussed in Section 7.2, this is incorrect. Directional rotation can only result from an external energy source being used to drive the system temporarily away from equilibrium.
    • It has recently been suggested that unidirectional pirouetting could result from simply derivatizing rotaxanes with chiral or knotted stoppers (see: O. Lukin, T. Ku-bota, Y. Okamoto, F. Schelhase, A. Yo-neva, W. M. Müller, U. Müller, F. Vögtle, Angew. Chem. Int. Ed. 2003, 42, 4542-4545). As discussed in Section 7.2, this is incorrect. Directional rotation can only result from an external energy source being used to drive the system temporarily away from equilibrium.
    • (2003) Angew. Chem. Int. Ed. , vol.42 , pp. 4542-4545
    • Lukin, O.1    Ku-bota, T.2    Okamoto, Y.3    Schelhase, F.4    Yo-neva, A.5    Müller, W.M.6    Müller, U.7    Vögtle, F.8
  • 256
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    • For an example of an electrochemically switched [2]catenane based on the redox reactions of metal centers embedded in one of the rings, see:
    • For an example of an electrochemically switched [2]catenane based on the redox reactions of metal centers embedded in one of the rings, see: B. Korybut-Daszkiewicz, A. Wieckowska, R. Bile-wicz, S. Domagala, K. Wozniak, Angew. Chem. Int. Ed. 2004, 43, 1668-1672.
    • (2004) Angew. Chem. Int. Ed. , vol.43 , pp. 1668-1672
    • Korybut-Daszkiewicz, B.1    Wieckowska, A.2    Bile-wicz, R.3    Domagala, S.4    Wozniak, K.5
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    • See for example the observation of single-molecule stretching and contraction described in Section 7.2 and ref. [38], and additionally:
    • See for example the observation of single-molecule stretching and contraction described in Section 7.2 and ref. [38], and additionally: D. M. Eigler, C. P. Lutz, W. E. Rudge, Nature 1991, 352, 600-603;
    • (1991) Nature , vol.352 , pp. 600-603
    • Eigler, D.M.1    Lutz, C.P.2    Rudge, W.E.3
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    • P. Ball, Nature 2000, 406, 118-120;
    • (2000) Nature , vol.406 , pp. 118-120
    • Ball, P.1
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    • Molecular Switches
    • in, (Ed.: B. L. Feringa), Wiley-VCH, Weinheim
    • A. P. de Silva, N. D. McClenaghan, C. P. McCoy in Molecular Switches (Ed.: B. L. Feringa), Wiley-VCH, Weinheim, 2001, pp. 339-361;
    • (2001) , pp. 339-361
    • De Silva, A.P.1    McClenaghan, N.D.2    McCoy, C.P.3
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* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.