Topological isomers knots

Dobrowolski JCz (2003) On the classification of topological isomers Knots, Links, Rotax-anes, etc. Croat Chem Acta 76 145-152. 

Dobrowolski, J.C. (2003) Classification of topological isomers knots, links, rotaxanes, etc. Croatica ChemicaActa, 76,145-152. 

Liu, L., Depew, R.E., Wang, J.C., 1976. Knotted single-stranded DNA rings a novel topological isomer of circular single-stranded DNA formed by treatment with Escherichia coli w protein. J. Mol. Biol. 106 439-452. 

Figure 3.45 (a) A trefoil knot and (b) its topological enantiomer are topological isomers of (c) a macrocycle. 

Quantitative demetallation of the various copper(I) complexes by KCN leads to the corresponding free ligands represented in Figure 13. Demetallation of 25 + affords the free trefoil knot 26 as a glass. Very small amounts ( 0.5%) of 27, the unraveled topological isomer of 26 could also be isolated. 

Figure 21. The equilibrium between the helical interlaced system precursor of the trefoil knot and its face-to-face analogous complex leading to the face-to-face complexes. Interconversion between the two isomeric cyclic products is, of course, not possible. For the cyclic compounds, the total number of atoms x connecting two phenolic oxygen atoms is 16 if n=4 (pentakis(ethyleneoxy) fragment) or 19 if n = 5 (hexakis(ethyleneoxy) linker). Each knot is represented by the letter k accompanied by the overall number of atoms included in the cycle. The face-to-face complexes contain two monocycles (letter m), the number of atoms in each ring also being indicated. It can be noted that each knot has a face-to-face counterpart. For instance [Cu2(k-90)]2+ and [Cu2(m-45)2]2+ are constitutional isomers. They are by no means topological stereoisomers [34, 35].

The evolving domain of radial, as well as linear, addition of modules to form an expanding moiety, in a manner akin to the development of polymers, referred to as "dendrimers", is examined and nomenclated The direct inclusion of topology in the description of isomers, once a very insignificant part of chemical nomenclature, is now a factor to be reckoned with, not only for the small class traditionally referred to as "topological" (including catenanes, rotaxanes, and knots), but also as new compositions of matter, such as the endothelial fullerenes, are formulated. 

A comparison between the two isomers 86 and 87 produced strong evidence for the knotted topology of 86. Both compounds have identical mass spectra (FAB) molecular peaks appear at the same value. In addition, the general pattern... 

Liquid extraction was used to make diastereomers, exploiting the high solubility of potassium triflate in water compared with the binaphthylphosphate salts. The two diastereomers have different solubilities and the (+) isomers of knot and anion crystallise together [49, 50], while the laevorotatory knot remains soluble. Counterion exchange with hexafluorophosphate gave the pure topological enantiomers. The optical rotatory power of the copper knots is very high At the sodium D-line (589 nm), the optical rotatory power was 7.000 mol 1 L dm They are beautiful molecules with a remarkable property ... 

How are these stereoisomers different from conventional diastereomers The circle and the knot can be infinitely deformed— bent, twisted, stretched, and compressed— but they will never be interconverted (as long as we don t cross any bonds). Conventional isomers can be interconverted by deformation, as in the case of 2-butanol in Figure 6.9. Conventional stereoisomerism depends on the precise location of the atoms in space, leading to the terms geometric or Euclidian isomerism. With topological stereoisomers, we can move the atoms all around, and retain our isomerism. 

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