Catenane molecular train

Ashton PR et al (1991) Molecular trains - the self-assembly and dynamic properties of 2 new catenanes. Angew Chem Int Ed Engl 30 1042-1045... 

The consequences of increasing the size of the polyether macrocycle to 68 members (that is, by a factor of two over the small ring system) was investigated. Accordingly, the synthesis of tetrakis-/ -phenylene-68-crown-20 was achieved in dimethylformamide at room temperature in excellent yield and this, in turn, was initially used to produce the [2]-catenane 22 (Figure 5.13). From the temperature dependence of the H NMR spectrum, 22 appears to behave like a molecular train - with the tetracationic cyclophane travelling from station to station around the... 

In addition to these molecular shuttles, other dynamic supramolecular systems have been reported with the development of molecular trains utilizing catenanes [79], where one catenane ring can continually cycle around another via several stations. Sauvage and co-workers ]80-83] reported electrochemically induced ring gliding in copper catenanes which exploits the differing preferred geometries associated with Cu(I)/Cu(II). 

In Milestone Six, a change in electrical conductivity, presumably tied to a molecular translation, was reported. A cyclic bistable [2]calcnane, with two different electron donor moieties (the closed "track") and a cyclic acceptor traveling on the catenane (the "train" on the closed track) (Fig. 8) was measured as a LB monolayer between polysilicon and Ti electrodes. The two donor moieties are naphthalene, a weak donor, and tetrathiafulvalene, a much stronger donor (in the sense that it is more easily... 

For a [2]catenane containing a smaller bipyridinium ring in a bigger ring made of four hydroquinones in acetonitrile at 80 °C it was shown [119] that the former moves around the latter 14 x 103 times a second and self-revolves 9 x 106 times a second. In the [3]catenane shown in Fig. 40, where one more bipyridinium ring is incorporated, the two smaller rings were found to move around without collision 10 x 103 times a second as though they were trains as a molecular scale [119]. 

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