π systems are important building blocks in supramolecular assembly because of their versatile noncovalent interactions with various functional groups. A notable example of applying π–π interactions in supramolecular assembly is the synthesis of catenane. The major challenge for the synthesis of catenane is to interlock molecules in a controlled fashion. Stoddart and co-workers developed a series of systems utilizing the strong π–π interactions between electron-rich benzene derivatives and electron-poor pyridinium rings.
Ashton PR, Goodnow TT, Kaifer AE, Reddington MV, Slawin AM, Spencer N, et al. (1989). “A [2] Catenane Made to Order”. J. Angew. Chem. Int. Ed. 28 (10): 1396–1399. doi:10.1002/anie.198913961.
Figure 2. The Stoddart synthesis of [2] catenane…
[2]Catanene was synthesized by reacting bis(pyridinium) (A), bisparaphenylene-34-crown-10 (B), and 1, 4-bis(bromomethyl)benzene (C) (Fig. 2). The π–π interaction between A and B directed the formation of an interlocked template intermediate that was further cyclized by substitution reaction with compound C to generate the [2]catenane product.
