Rotaxanes switchable

By using an incrementally staged strategy, the architectural features of switchable rotaxane 9H3+ (Fig. 13.9)15 were incorporated into those of a previously investigated16 triply threaded two-component supramolecular bundle. The result was the construction of two-component molecular devices like 10H39+ (Fig. 13.11) that behave like nanoscale elevators. 17 Compound 10H39+, which measures about... 

Tetrathiafulvalene and its derivatives are electroactive and can be easily and reversibly oxidized to TTF + and TTF2 +. The TTF skeleton now occupies a critical position as far as switchable properties are concerned, and behaves as a key unit for a number of supramolecular concepts. For instance, the recent years have seen an increasing contribution of TTF to the preparation of interlocked compounds such as rotaxanes and catenanes. These systems are of particular importance as candidates for molecular machines. 

Figure 11.38 A [2] rotaxane-based, pH- and redox-switchable molecular shuttle.

Fig. 2 Schematic representations of (a) a switchable [2]catenane and (b) a switchable [2]rotaxane.

Figure 17.7 A molecular valve based on redox switchable bistable rotaxane 84 1 77 (Adapted with permission from V. Balzani et al., ChemPhysChem 2008, 9, 202-220. Copyright Wiley-VCH Verlag GmbH Co. KGaA.)...

The self-assembly of a hybrid rotaxane (and related pseudocatenanes) incorporating both ammonium and bipyridinium cationic units in the linear components is known. The switchable [2]-rotaxane 46 incorporates one of each of these... 

Rotaxanes changing shape through switchable thread-macrocycle interactions have also been reported [50]. 

Photoisomerizations can often occur by several different mechanisms. Systems that isomerize via a controlled mechanism are potential candidates for molecular machines [184]. Energy in the form of light is absorbed and converted to controlled mechanical force on the molecular scale. Examples of a mono-directional rotor [185, 186], a switchable rotor [187], and a molecular shuttle [188] have been demonstrated. These systems are light-controlled, but there are also examples of systems which control molecular motion based on electro- and/or chemical modulation, such as the threading/imthreading of (pseudo)rotaxanes [189-196]. 

In principle, CD rotaxanes can be used for molecular information processing if they are reversibly switchable between two states, such as CD [2]-rotaxanes comprising two different binding sites within their axes, as shown in Fig. 14. In the off state, the threaded CD recognizes the better binding site and settles there. Once the... 

Yasuda T, Tanabe K, TsujiTet al (2010) A redox-switchable 2 rotaxane in a Hquid-crystalline state. Chem Commun 46 1224-1226... 

Fig. 3. A switchable rotaxane based on acceptor-donor complexes [24]. Before oxidation, the electron acceptor (ring) interacts preferentially with the benzidine nucleus (donor). After electrochemical oxidation of the latter, the ring is shifted towards the biphenol group. The process is reversible...

Switchable Molecular Devices From Rotaxanes to Nanoparticles... 

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