Oligorotaxanes

Since the inclusion complex between 4,4/-bipyridinium salt and bis-p-phenylene crown ether is stable, oligorotaxane can be prepared from oli-go(4,4 -bipyridinium salt) quantitatively. Stoddart et al. reported that olig-orotaxanes were prepared when oligo(4,4/-bipyridinium salt) bearing the pyridine groups at the termini were alkylated by bulky alkylation agent in the presence of bis-p-phenylene crown ether [49-51]. 

Acylation of hydroxy groups of axle components is one of the most effective end-capping methods of rotaxane synthesis. While acylation of alcohol is usually carried out in the presence of tertiary amines such as triethyl-amine, the use of amine significantly decreased the yield of the rotaxane. Takata et al. have demonstrated that the use of the combination of trib-utylphosphine as a catalyst and acid anhydride as an acylation reagent is an excellent solution to this problem [60]. The acid-catalyzed acylation is also effective [61]. The oligorotaxanes were easily prepared in more than... 

Slipping approach is effective for the preparation of oligorotaxane based on crown ether and secondary ammonium salt because the inclusion complex is fairly stable. When dibenzo-30-crown-10 (DB30C10) was used as the wheel component, 3,5-di-ferf-butylphenyl group is the complementary end-cap to the crown ether. DB30C10 slips over the 3,5-di-ferf-butylphenyl group... 

In this type of rotaxane, the intramolecular hydrogen-bonding interaction between ammonium salt and crown ether is too strong to neutralize the ammonium part with usual bases. In fact, Takata et al. found that the rate of proton-exchange between [2]rotaxane and water was far slower than that between pyrrole and water, suggesting the extremely lowered acidity of the ammonium moiety [74]. However, the ammonium group can be quantitatively acylated by the excess amount of electrophile in the presence of excess triethylamine. Some oligorotaxanes can be prepared by this process (Scheme 12). 

Sauvage et al. have synthesized a variety of oligorotaxanes utilizing 1,10-phenanthroline-copper(I) complex [179]. Stable bis(l,10-phenanthroline) copper(I) complex has a tetrahedral coordination structure, and two... 

Cyclophanes are the class of synthetic receptors that have a hydrophobic cavity. Water-soluble cyclophane can make organic compounds soluble in water via the formation of inclusion complex. Anderson et al. synthesized rod-like organic compounds in water in the presence of water-soluble cyclophanes, and obtained corresponding rotaxanes. When oxidative coupling of an acetylenic derivative in the presence of a cyclophane, an oligorotaxane having an axle with a conjugated structure was dominantly obtained rather than non-complexed diacetylene.[187,188] (Scheme 31). This rotaxane is a prototype of insulated molecular wire that is expected as an electric wire in a molecular device. 

Franco I, Schatz GC, Ratner MA (2009) Single-molecule pulling and the folding of donor-acceptor oligorotaxanes phtaiomenology and interpretation. J Chem Phys 131 124902... 

Whang D, Park K-M, Heo J, Ashton P, Kim K. Molecular necklace quantitative self-assembly of a cyclic oligorotaxane from nine molecules. J Am Chem Soc 1998 120 ... 

Oligorotaxanes of the order Mn 9000 Daltons (nine repeat units) have been prepared by reacting a polyether chains, symmetrically substituted with hydroquinol rings with methylene bis(4-phenyl-isocyanate). The solubility of the system in typical solvents imposed limitations on characterisation. The intense orange colours did indicate that we had accomplished the objective of self-assembling pseudo-oligorotaxanes. 

Table 2 Distribution of oligorotaxane products isolated after kinetically stoppering pseudorotaxanes formed between DNP oligomers and CBPQT ... 

Fig. 8 The three families of oligorotaxanes, exemplified by compounds derived from a heptameric DNP thread. The rotaxanes moods depend on their adherence to a selection rule forbidding CBPOT " to occupy adjacent DNP sites. Whereas Confiased rotaxanes can adopt multiple stable translational isomers and Frustrated rotaxanes cannot obey the rule at all, Happy rotaxanes express a single rule-compliant isomer...

Fig. 10 Stacked plot of the partial H NMR spectra (CD3CN, 600 MHz, 233 K) of the Happy oligorotaxanes, showing the migration of the BIPY a- and p-protons to lower hequencies as the oligomers grow longer. Resonances in darker shades correspond to protons located closer to the center of the oligomers...

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