2- -1,3-phenylene-16-crown

It should be mentioned here that very interesting constitutional and translational isomerism is observed in the series of catenanes and rotaxanes which contain phenol derivatives such as macrocycUc phenylene-crown components as well as phenolic polyether chains (see also Lehn s recently published book ). 

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. 

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]. 

Another family of calixarene-based ditopic receptors are the l,3-calix[4]arene-Z w(crown ethers), where the calixarene is locked into the 1,3-alternate conformation, and substrate binding normally occurs at the crown ether loops. These may form mononuclear or dinuclear complexes with alkali inetal cations, or may bind neutral guest molecules. The unsymmetrical 1.3-alternate calix[4]ar-ene-l,3-crown-6 2,4-(l,2-phenylene)-crown-6 forms a 1 1 complex with Cs. The crystal structure shows that the cation is bound only within the adapted phenylene-crown-6 loop, and a molecule of acetonitrile is bound within the unmodified crown-ether loop. ... 

In this case, the forces are induced by electron donor-acceptor interactions between a synthetic receptor molecule like bis(phenylene) crown ether (ring) and its substrate in the form of appropriate substituted paraquats (thread). 

In earlier works di(p-phenylene) crown such as di(p-phenylene)-34-crown-10 60 was principally employed as a host molecule for alkali metal, alkaline earth metal and ammonium [54] and pyridiniiun cations including paraquat and diquat dications [55,56]. In recent years, it has been exclusively used as donor components for rotaxanes or catenanes having secondary ammonium, bipyridinium rod or bipyridinium macrocycle [57-75]. 

Fig. 15. A branched [4]rotaxane from self-assembly of the triply-branched trisfbipyridini-um)derivative and bis-p-phenylene-34-crown-lO...

With the alkynyl functionality greater than two, starbust type complexes are obtained, as derived, for example, from 1,3,5-trialkynylbenzenes 85 or -triazines,86 1,1,2,2-tetraalkynylethenes,85 or bis(l,2-dialkynyl)phenylene-bridged crown ethers or calixarenes. ... 

Figure 27 illustrates a rotaxane of Stoddart et al. [93], in which the axle contains two stations interacting with the cyclobis(paraquat-p-phenylene) bead. Its NMR spectrum at room temperature indicated that the bead moves back and forth like a shuttle between the stations about 1800 times a second. Stoddart et al. [94,95] prepared a [2]rotaxane containing two bipyridinium units and a crown, as shown in Fig. 28. The shuttling speed of the bead estimated by...

Ort/io-phenylene diboranes constitute another important class of polydentate Lewis acids which have been considered for the complexation of anions.In this context, most efforts have centered on the study of the ligative behavior of 1,2-bis(bis(pentaliuorophenyl)boryl)tetraliuorobenzene (17). Similar to 22, compound 17 forms chelate fluoride ([17- r2-F] ) and hydroxide ([17- r2-OH] ) complexes when treated with KF/18-C-6 and KOH/18-C-6, respectively (18-C-6 = 18-crown-6) (Scheme 35). The crystal structure of these anionic complexes has not been... 

FIGURE 3. Example of an inverse crown containing a 1,4-phenylene dianion... 

The macrocyclic polyether bis-p-phenylene-34-crown-10 (4) has a cavity large enough to accommodate [11] (Figure 6) simultaneously two acyclic guests 2 PF6, affording the [3]pseudorotaxane [(2)2-4][PF6]2. In this instance, however, the equi-... 

The same concept was used in polycondensation systems for the preparation of branched and cross-linked polymers [121]. Copolyurethanes 73 were prepared from tetra(ethylene glycol), bis(5-hydroxymethyl-l,3-phenylene)-32-crown-10 (74)... 

Gibson and coworkers utilized the expected complexation between crown ethers and acrylonitrile for the preparation of poly(acrylonitrile-crown ether rotax-ane)s 94 [137]. Relative to that with the polystyrene backbone, the enhanced threading supported the intermediacy of the expected complex. The reaction intermediates, the cations 95 and 96 in the preparation of poly(phenylene vinylene) (PPV) also provided a source for interaction with crown ethers [70], The solution polymerization of precursor 95 in the presence of crown ethers followed by transformation of 96 produced polyrotaxanes 97. 

Over the last decade, noncovalent bonding interactions between appropriate Jt-elec-tron-deficient and Jt-electron-rich recognition sites have been exploited in our laboratories for the synthesis of catenanes and rotaxanes. 271 In the example illustrated in Figure 10, the bis(hexafluorophosphate) salt 11-2PF6 was treated 28 with trons-bis(pyridine)ethylene (12) in the presence of the previously formed macrocyclic polyether bis-p-phenylene-34-crown-10 (13). The resulting [2]catenane 14-4PF6 was isolated in 43 % yield after counterion exchange. 

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