Rotaxanes light-driven

Fig. 5 Controlled molecular motion in rotaxanes light-driven shifting of the wheel along the rotaxane axle (top) and contraction of a molecular muscle stimulated hy electrochemical Cu(I)-Cu(II) interconversion (bottom).

In this rotaxane, a-CD exists at the trans-azobenzene part but it moves to the methylene part when the trans-azobenzene unit is converted into cts-azoben-zene. This light-driven locational change was regarded as a molecular shuttle system. 

Keywords Catenane Ir/Ru Light-driven molecular machine Photoinduced Charge Separation Rotaxane Scorpionate... 

Light-driven Unthreading Reaction in Rotaxane with a [Ru(diimine)3]2+ Core... 

Scheme 6.5.7. Light-driven shuttling of a rotaxane with internal hydrogen bonding.

Fig. 14a-d. Intramolecular mechanism for the light-driven switching of the ring R between the two stations Aj and A2 in the [2]rotaxane represented in Fig. 13 [7f]. The dashed lines indicate processes that are in competition with those needed to perform shuttling...

Transition metal-complexed catenanes and rotaxanes as light-driven molecular machines prototypes 05CL742. 

Murakami, H, A Kawabuchi, K Kotoo, M Kunitake and N Nakashima (1997). A light-driven molecular shuttle based on a rotaxane. Journal of American Chemical Society, 119(32), 7605-7606. 

The earliest light-driven CD-based molecular shuttle consisted of an azobenzene moiety in the axis and a-CD (Fig. 4). NMR spectroscopy supported the formation of a rotaxane complex where a-CD stays at the central trans-azobenzene site. Trans-cis conversion with 360 nm light caused a shift of a-CD to the methylene spacer, due to the exclusion of the cts-azobenzene moiety from the CD cavity. Back photoreaction and repositioning of the macrocycle on the trarzs-azobenzene unit was obtained with irradiation at 430 nm. 

Nakashima et al. reported the first light-driven molecular shuttle based on a rotaxane (Figure 55) comprising an a-CD linked mechanically with an axle containing an azobenzene unit located at the center, two paraquat units at each side of the azobenzene unit, and 2,4-dinitrophenyl stoppers. The location of a-CD could be changed between the azobenzene and ethylene moieties by lights of different wavelengths or by the heat both in water and in DMSO. 

Figure 55 The first light-driven molecular machine based on a rotaxane. ...

Tian et al. reported a lockable light-driven molecnlar shnttle (Figure 59) based on a [2]rotaxane comprising an a-CD bound mechanically with an axle to a stilbene nnit. At neutral pH, owing to the hydrogen bonds formed by the carboxyl groups of the stoppers and the hydroxyl groups of the a-CD, the a-CD resided on the stilbene center even... 

Figure 7 Synthesis of pseudo[3]rotaxane R5 (FVA-2CD) and the interconversion of the dual-driven (redox- and light-driven) ensembles.

Light-Driven Rotaxanes Incorporating a Photosynthesiser - Towards Photochemical Machines... 

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