Molecular Catenanes and Knots

A catenane is a molecule in which two or more rings are interlocked, in a manner resembling a daisy-chain. Chemists have speculated about the possibility of the synthesis of such motifs for a long time. The two arrangements of the interlinked cyclic molecules 

The two topological isomers A and B of interconnected rings (reproduced with permission from reference , copyright 1961, American Chemical Society). 

Strategies for the synthesis of interconnected rings using a metal template the groups f and g selectively bind to each other (from reference i] p 801) 

Formation of the metallated two inner-linked rings (catenate) 5,23. 

An example to illustrate the above strategy consists of treatment of [Cu(NCMe)4] with 2,9-diphenol-1,10-phenanthroline (20), to give the tetrahedral copper complex [Cu 

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Sauvage, J.-P. Dietrich-Buchecker, G. Molecular Catenanes and Rotaxanes and Knots-, Wiley-VCH Weinheim, 1999. 

A useful summary of the various and numerous types of rotaxanes, catenanes, and knots can be found in a review of template routes to interlocked molecular structures 468). Inorganic chemistry is centrally involved in the templating involved in self-assembly and in controlled synthesis of such species. 

The plectonemic nature of the DNA double-helix makes it a tractable molecule for experiments in molecular topology. This is a very rich vein for the exploration of the topological properties of matter. In this chapter, we have tried to illuminate some of the techniques by which the single-stranded topology of DNA can be directed in synthetic molecules. Catenanes and knots, periodic braids, and Borro-mean rings are available from simple protocols, and it is to be hoped that the physical properties associated with complex topologies (Moffatt 1990) will become available through the medium of DNA constructions. 

Jean-Pierre Sauvage is a CNRS director of research and is located at the Universite Louis Pasteur in Strasbourg, France. His current research interests include the development of models of the photosynthetic reaction centre using transition metals and porphyrins [5], topology (synthetic catenanes and knots) [6], and molecular machines [7]. 

A wide range of instrumental techniques are needed to characterise products fully - X-ray crystallography, mass spectrometry (especially FAB-MS and electrospray MS), H and NMR, UV-Vis spectroscopy, and electrochemistry - in the solid state and in solution. As much information as possible is needed in order to establish both the exact nature and long-range structural features (superstructure) of rotaxanes, catenanes and knots. As noted at appropriate points in the text, there is considerable interest in applications for these classes of compounds, particularly in respect to molecular switching devices. 

Sauvage, J.-P. Dietrich-Buchecker, C. O. Chambron, J.-C. Transition metals as assembling and templating species synthesis of catenanes and molecular knots. In Comprehensive Supramolecular Chemistry, Sauvage, J.-P. Hosseini, M.W., Ed., Publisher Elsevier, Oxford, UK 1996 Vol. 2, p 43. 

Fujita, M. Transition metal-incorporating catenanes. In Molecular Catenanes, Rotaxanes and Knots Sauvage, J.-P., Dietrich-Buchecker, C., Eds. Wiley-VCH Verlag Weinheim, Germany, 1999, pp 57-76. 

Some racemates (Figure 3.23) are more efficiently resolved on the bonded-type CSP than the coated-type CSP by using chloroform as a component of the eluent. On the bonded-type CSP of 24n, topologically interesting catenanes and molecular knots are successfully resolved using a hexane-chloroform-2-propanol mixture.185 The first direct HPLC resolution of the smallest chiral... 

Sauvage JP, Dietrich-Buchecker CO (1999) Molecular catenanes, rotaxanes and knots. VCH-Wiley, Weinheim... 

The functionalisation also allows extending the complexity of intertwined molecular assemblies involving molecular catenanes, rotaxanes and knots. Elaborate interlocked assemblies constructed by means of metal-templation techniques and ji-ji-stacking preorganisation were reviewed [3, 11], Our last survey was devoted to the hydrogen bond templated synthesis of amide-based catenanes and rotaxanes [32], Since then a considerable advancement in elucidation of mechanisms of templation and derivatisation of the amide-based interlocked structures has been reached. Moreover, in 2000 we reported a one pot synthesis of amide-based knots such as 8 [21], which is so far the easiest preparation of molecular knots. In the following, specific possibilities of functionalisation of amide-based catenanes, rotaxanes and knots will be discussed. 

In the introduction we mentioned extravagant interlocked structures of higher complexity such as doubly intertwined catenane and molecular composite knots of Sauvage et al. and multicatenanes made up of 4 to 7 interlocked rings obtained by Stoddart et al. In this section, we will discuss assemblies made up of amide-based catenanes, rotaxanes and knots. Here we use the term assembly to describe covalent or... 

Heim, C., Udelhofen, D., Vogtle, F. Amide-Based Catenanes, Rotaxanes and Pretzelanes in J.-P. Sauvage, C. Dietrich-Buchecker (eds.), Molecular Catenanes, Rotaxanes and Knots. A Journey Through the World of Molecular Topology, Wiley-VCH, 1999, pp. 177-222. 

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