Hydrogen-bonded amide template, catenane

In the early 1990s Hunter [49] and Vogtle [50,51] discovered independently the possibility of using hydrogen bonding interactions displayed by amide groups to template the formation of [2 ] catenanes. While studying the reaction between the... 

This conformation resembles that determined by X-ray single-crystal structure analysis. Apart from a close interaction of the -system of the amide groups with the para-substituted aryl moieties, no further n-n interactions are observed. The template-assisted catenane formation is on this account mainly driven by hydrogen-bonding, and n-n interactions are of minor importance only. 

The nonionic template strategy based on hydrogen bonds and to a certain extent on n-n interactions has made catenanes and rotaxanes readily available. The molecular recognition and self-organization process which is responsible for the formation of intertwined and interlocked structures is founded upon the same weak interactions that govern many biological processes. Amide-based catenanes and rotaxanes can thus serve as valuable models for complex molecular recognition patterns in nature. 

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. 

Figure 4. Hydrogen bond templated threading of a tetraamide ring in synthesis of amide-based catenanes and...

Scheme 5.4 Synthesis of a [2]catenane by self-organization of amides around a chloride anion as the template. The pseu-dorotaxane formed between the linear and the cyclic amides is held together additionally by various hydrogen bonds and n-n interactions.

Figure 6 Bemylic amide [2]catenane formation in one step from isophthaloyl dichloride and xylylene diamine. The smallest. self-replicating system known the first-formed macrocycle templates the formation of an identical second one through it by hydrogen bonding...

The knotted structure was patent in the crystal structure (Figure 12), which showed a pattern of hydrogen bonds between amide groups. A similar pattern is also found in the structure of [2]catenanes and rotaxanes synthesized using the same basic template. ... 

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