Isomerism translational

Figure 17. Synthesis of [2]catenane 45 which is distinguished by a solvent-dependent translational isomerism.

Partial aliphatic catenanes reported by Leigh et al. in 1996 exhibit an interesting solvent-dependent translational isomerism [29]. Stannylation of 43 converts the diol into 44, which is readily soluble in nonpolar solvents (Figure 17). Subsequent treatment with various aliphatic l,co-dicarboxylic acid dichlorides led to catenanes 45 and macrocycles bearing lipophilic chains. 

Figure 18. Translational isomerism of 45 depending on the polarity of the environment 45 adopts either conformation I (nonpolar environment) or conformation II (polar environment).

Schill, G., Rissler, K., Fritz, H., Vetter, W., Synthesis, isolation, and identification of translationally isomeric [3]catenanes. Angew. Chem., Int. Ed. Engl. 1981, 20, 187-189. 

For the solvent-dependence of the translational isomerism associated with some catenanes and rotaxanes, see (a) Ashton,... 

Scheme8 Translational isomerism in an amphibilic benzylic amide [2]catenane 16 [55]...

Translational isomerization of a series of [2]catenanes possessing an electron-rich dibenzo-34-crown-10 ether interlocked with rings containing an unsymmetrical 4-substituted resorcinol-based tether linking two electron-poor dipyridinyl groups was demonstrated and studied by VT NMR <07CC4289, 07JOC6454>. 

Leigh, D. A., Moody, K., Smart, J. R, Watson, K. J., and Slawin, A. M. Z. Catcnane chameleons Environment-sensitive translational isomerism in amphiphilic bcnzylic amide [2]catenanes. Angew. Chem. Int. Ed. Engl. 1996, 35, 306-310. 

It should be mentioned here that very interesting constitutional and translational isomerism is observed in the series of catenanes and rotaxanes which contain phenol derivatives such as macrocycUc phenylene-crown components as well as phenolic polyether chains (see also Lehn s recently published book ). 

Whereas the term co-conformer is usually reserved for translationally isomeric species, it appears in inverted commas in this instance to signify that the two circumstances in which the catenane can exist are of different oxidation states, and so are not isomeric... 

The solid state self-organization of a self-assembled [2]-catenane <94CC2475,94M1159>, the two step self-assembly of [4]- and [S]-catenanes <94AG(E)433>, and the highly selective translation isomerization of [2]-catenanes <94CC2479> has been reported. 

Fig. 6 A photochemically driven translation isomerism in a [2]rotaxane supramolecular machine according to Ashton et al. The flash photolysis data, together with electrochemistry observations, allowed the authors to obtain a complete electronic picture of the processes governing the switching mechanism in this [2Irotaxane, from both energy and kinetic perspectives.

Bottari G, Dehez F, Leigh DA, Nash PJ, Perez EM, Wong JKY, Zerbetto F. Entropy-driven translational isomerism a tristable molecular shuttle. Angew Chem Int Ed 2003 42 5886-9. 

Figure 4-16. Solvent control of translational isomerism in [2]-catenanes having a hydrogen link (-(CH2) - shown as in...

The strategy for the construction of an electrochemically-addressable molecular switch is outlined in Figure 2. Both "stations" A and B should recognise the tetracationic cyclophane but A must recognise it stronger than B and A must have a lower oxidation potential than B. Thus, the tetracationic cyclophane should reside on station A to start with. Perturbation by an external stimulus, e.g., from an electrode, should cause the cyclophane to move from station A to station B. With reference to the degenerate molecular shuttle shown in Scheme 2, it is evident there are two ways to tackle the problem of controlling the translational isomerism. They are to -... 

Figure 7. Illustration of the translational isomerism possible by changing the Ti-electron rich units on the crown. Unit A differs from unit B either sterically or electronically or both.

In principle, the control of translational isomerism may be accomplished by steric and/or electronic means. We chose the macrocyclic polyether 1/5NPP36C10, containing one hydroquinol ring and one 1,5-dioxynaphthalene ring system, in order to investigate the influence of steric and electronic factors on the positon of the equilibrium between two translational isomers. It was expected that, if this crown ether could be incorporated into a [2]catenane, then the difference in both the size and the tc-donating ability (naphtho > benzo) of the two units would strongly influence the relative populations of the translational isomers in solution. 

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