Mobius strips

For a review of chirality in Mobius-strip molecules catenanes, and knots, see Walba, D.M. Tetrahedron, 1985, 41, 3161. 

FIGURE 15.7 A Mobius strip. Such a strip is easily constructed by twisting a thin strip of paper 180° and fastening the ends together. 

Further elaborate molecules of the present category continue to be synthesized. For example, the Mobius strip crowns (210) and (211) were obtained using the procedure outlined by [4.6] (Walba, Richards Haltiwanger, 1982). 

Wires or strips at the nanometre scale are surprisingly flexible (surprising if we insist on thinking in terms of our macroworld ) and can even be twisted in order to form Mobius strips, as recently achieved with NbSea single crystals (Tanda et al, 2002). 

Just as on the Mobius strip, strange things would happen if we lived on the surface of a small hypersphere. By analogy, consider a Flatlander living in a universe thar is rhe surface of a small sphere. If the Fladander travels along the... 

Figure 5.8 A 2-D human on a Mobius strip universe. If the human travels around the strip, his internal organs will be reversed.

The main molecular chain in compound 26 has the form of a Mobius strip (see Figure 15.8).65 This molecule has no chiral carbons, nor does it have a rigid shape, but it too has... 

Mechanism of the Rapid Interconversion Mobius Strip Mechanism... 

For catenane formation from two separate rings, the most reasonable explanation involves dissociation of a ring, threading another ring on the thread, and reconnection of the ends of the thread (Scheme 2 a). However, careful mechanistic consideration of the rapid interconversion suggested a Mobius strip mechanism which involves molecular topology reminiscent of the well-known Mobius strip. 

This distinction between statistical, directed and Mobius strip strategies is also applied to the synthesis of knots. 

Figure 6. The Mobius strip approach (three half-twists) to a trefoil knot.

In contrast, the Mobius strip approach, depicted in Figure 6, also suggested by Frisch and Wasserman in 1961 [36], seemed much more realistic. 

A directed knot synthesis relying upon the Mobius strip principle was conceived by Schill and coworkers [41-50] who synthesized the doubly bridged tetraamino-p-benzoquinone 9. Connection of three such molecules by long chains should give the molecular ladder 10, precursor of the three half-twist-containing Mobius strip 11 (Figure 8). 

As seen above, the randomness of the Mobius strip approach and numerous difficult steps in Schill s directed approach were highly limiting factors in a trefoil knot synthesis. Both these major obstacles might be circumvented by the use of an unambiguous templated synthesis procedure. 

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