Bis--catenanes

In order to extend their studies to more complex systems, the Stoddart group directed their efforts towards the synthesis of the bis-[2]-catenane 16. The approach 

Ballardini, V. Balzani, A. Credi, M.T. Gandolfi, L. Prodi, M. Venturi, L. Perez-Garcia and J.F. Stoddart, Gazz- Chim. Ital, 1995, 125, 353. 

The above successful incorporation of the tetra-substituted benzene ring to produce the fused tetracationic cyclophane units, relies on being able to react the former in a para/para fashion rather than in an ortho/ortho or meta/meta one. The present product represents the successful interlinking of three major components. If one considers that a one-step synthetic procedure was employed, then it is a total of five molecular species that are, in fact, involved in the self-assembly process. 

Other expanded catenanes, 19 and 20, each incorporating a bis-macrocyclic 

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Corresponding symmetrical, bis-porphyrin derivatives, as well as larger entities incorporating bis-porphyrin and bis-catenane groups - see 12 - have also been investigated. ... 

Limitations on the application of hydrogen bonded capsular assemblies come from the poor stability of these assemblies in polar media compared to those held by covalent bonds. In an attempt to overcome these Umitations, Bohmer described the synthesis of a mechanically locked chiral bis-catenane based on calixarene capsules [55]. Inspired by this pioneering work, our group produced a mechanically locked hybrid tetraurea calix[4]arene-calix[4]pyrrole capsule 30 (Fig. 32.14) [56]. This catenated capsule displayed reversible encapsulation (i.e. reversible assembly of the urea belt). The two hemispheres of the capsule never dissociate completely due to the bis-catenated topology. 

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See also in sourсe #XX -- [ ]

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