Rotaxanes pseudopolyrotaxanes

Stoddart and co-workers reported the attempt to construct a supramolecu-lar poly[2]rotaxane (pseudopolyrotaxane) in 1998 [211]. They synthesized a self-complementary (plerotopic) monomer consisting of a 24-crown-8-ether moiety and a secondary ammonium salt group (Scheme 41). Upon recrystal-... 

This review has been focused on the literature relevant to pseudorotaxanes, pseudopolyrotaxanes, polyrotaxanes and rotaxanes that may potentially be used for a variety of drug delivery and medical imaging applications. 

Gibson et al. reported that the copolymerization of poly(THF) and a diol-pseudorotaxane consisting of 4,4/-bipyridinium salt and bis-p-phenylene crown ether with diisocyanate afforded the corresponding polyurethane with the interlocked structure [48] (Scheme 6). Although this polyurethane has a pseudopolyrotaxane structure, the interlocked structure is stable because the interaction between 4,4/-bipyridinium salt and bis-p-phenylene crown ether is strong enough to keep the inclusion complex. In this elastic polyurethane, the rotaxane unit acted as a hard segment. 

Pseudo)polyrotaxanes containing CB[6J threaded on organic polymers were also reported. Such (pseudo)poly-rotaxanes were synthesized by interfacial polymerization of CB[6]/polyamine pseudorotaxane with diacid chlorides such as 1,6-hexanedioyl chloride (adipoyl chloride). "" Steinke and coworkers recently reported a novel way to produce polyrotaxanes utilizing 1,3-dipolar cycloaddition between azide and alkyne inside the cavity of They also synthesized pseudopolyrotaxanes... 

The pseudopolyrotaxane schematized in Fig. 3 has a supramolecular main-chain bond based on the dimerization of carboxyl groups. Philp and Stoddart had earlier suggested [27] that a molecular chain with appropriately spaced TT-rich rings could thread its way through several macrocycles containing n-acceptors (Fig. 9A) and subsequently be capped with large stoppers to form a permanent rotaxane polymer. The structure may be viewed as a molecular abacus with rotaxane units noncovalently linked to the molecular chain. Newer polyro-taxane polymers are described in this volume in Chapter 8. 

Harada et al. [18] reported the synthesis of a [2]rotaxane capped by j6-CD and a trinitrophenyl group. The /i-CD at the end binds the trinitrophenyl group stopper of another [2]rotaxanes gives a rotaxane aggregate, as shown in Fig. 2. Liu et al. [19] also developed a simple strategy to prepare polyrotaxane-like supramolecules. An inclusion compound had been synthesized by the complexation of 4,4 -di-pyridine and j6-CD in water the subsequent coordination of the complex with nickel ions in aqueous solution gave the corresponding pseudopolyrotaxane. 

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