Linkers rotaxane

A self-threaded rotaxane was also observed as a (by) product, when two homooxacalix[3]arenes were covalently connected to a molecular capsule via three p-xylylenediamide linkers Zhong, Z., Ikeda, A. and Shinkai, S. (1999)... 

Undoubtedly, the most important stereochemical feature is chirality. The [2]-rotaxane depicted schematically in Figure 2.12a is made with a macrocycle and a dumbbell that are not themselves chiral but oriented by appropriate substitution patterns on these components. Vogtle and co-workers described cycloenantiomeric rotaxanes that are based on the amide templating functionality (Figure 2.13).36 Racemic [2]-rotaxane 34 was synthesized in 20% yield by reaction of unsymmetrical acid dichloride 32 with trityl aniline 33 in the presence of macrocycle 31. The object and its mirror image are created by different sequences of the amide and sulfonamide linkers in both the dumbbell and the macrocyclic component. If the order of the atoms within the dumbbell is examined, in one enantiomer the sulfonamide nitrogen atom is... 

Lewis and his co-workers have continued their investigations into DNA hairpins with a variety of stilbene diether linkages. In the present report they have examined systems based on the linkers (3) and (4). The rotaxane formed between the stilbene derivative (5) and a-cyclodextrin (CD) does not undergo ,Z-isomerization. Contrary to this the complex of (6) with the p-CD isomerizes slowly on irradiation. The behaviour of the stilbene (6) is different and irradiation in a-CD brings about isomerization with a quantum yield of 0.06 for the E,Z process. The quantum yield for the reverse isomerization is 0.71. These values are to be compared with 0.17 and 0.79 for the isomerization in solution. The authors suggest that the irradiation of (6) in the CD brings about a movement... 

Fig. 3 Elements of molecular templates (a) a crossover reacts with a linker to give (i) a catenane and (ii) a rotaxane (b) a fused turn closed with a fused linker gives a macrobicycle (c) two anchors and two pairs of inverted ditopic turns template a trefoil knot (d) composite knots require two two-anchor templates and (e) oligocatenanes can be formed with multicrossover templates on a single anchor.

Coordination polymers containing rotaxane linkers 12CSR5896. Design and synthesis of cross-Hnked poly(benzoxazine)- and polybenzimidazole-based copolymer membranes and their application to an electrolyte membrane for a high-temperature PEM fuel cell 13P77. 

Figure 21 A schematic of the rotaxanes made by Fort et al., with the blue ovals representing lactose nnits, the red trnncated cones representing a-cyclodextrin, and the yellow pentagons representing the triazole linkers.

While the PRFs developed by Kim and coworkers were some of the first examples of one-, two- and three-periodic frameworks with rotaxane linkers, very httle material analysis (e.g., VT-PXRD) was reported to indicate the stabihty of these materials. However, recently... 

Figures (a) [2]Pseudorotaxane linker [6cTPDB24C8] + used to form PRF-11 (b) coordination environment of Cd° center in PRF-11 (c) X-ray structure of the square grid, two-periodic framework of PRF-11 containing rotaxane linkers [6cTPDB24C8p as well as naked 6 linkers...

Figure 9 (a) [2]Pseudorotaxane linker [7cDB24C8] + used to form PRF-12, PRF-13, and PRF-14 (b) coordination environment of Cd center in PRF-12 (c) X-ray structure of the distorted square grid, two-periodic framework of PRF-12 containing rotaxane linkers [7cDB24C8]2+ as well as naked 7 + linkers (d) coordination environment of center in PRF-13 (e) X-ray structure of the square and triangular forms which comprise layers in the three-periodic framework of PRF-13 (f) coordination environment of Sm center in PRF-14 (g) X-ray structure of the primitive cubic, three-periodic framework of PRF-14 (DB24C8 macrocycles only shown in one direction of the primitive cube for clarity)... 

All the examples of PRFs described to this point have taken advantage of the complexation of a linear, coordinating axle, and a macrocycle to form a [2]pseudorotax-ane linker. While this strategy has led to numerous PRFs, it is not, however, the only option. Loeb and coworkers used a permanently interlocked [2]rotaxane with the ligand donors appended to the macrocyclic component rather than the axle to form a different style of PRF. 

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