Mobius topological chirality

After synthesizing the 3-rung Mobius ladder, Walba conjectured that its molecular bond graph was topologically chiral [16]. In contrast with his conjecture, he... 

Figure 16. Some topologically chiral molecular graphs, (a) The Simmons-Paquette molecule.74 (b) Walba s 3-rung Mobius ladder molecule.75 (c) [4](l,l )[4](3,3 )[3](4 4 )-Ferrocenophan-16-one.76 (d) Triple-layered naphthalenophane.78 Unlabeled vertices represent carbon atoms, and hydrogen atoms are suppressed for clarity. Only one enantiomer of each molecule is shown.

The first flexible, topologically chiral K3j3 molecule is the so-called three-rung Mobius ladder 63 (Fig. 15). It was synthesized by D. M. Walba et al. in 1982 [85] and is represented on Fig. 15, together with several presentations of its graph (64-66). It is important to notice that the rungs of the ladder are different from... 

Fig. 15. The topologically chiral three-rung Mobius ladder (63) and several presentations of its graph (64-66). 64 and 66 are presentations with the minimum number of crossings (1). Note that the edges (1,1 ), (2,2 ) and (3,3 ) are differently coloured than the others (i.e. (l, 2), (2,3 ), etc,. ..)...

Keywords Catenanes Copper complexes Interlaced design Knots Kuratowski s graphs Mobius strip Topological chirality Topology... 

Experimental data about the properties of Mobius strip-like structures as the ladder 129a or knots like 127 are rather scarce. However, a theoretical analysis of the peculiarities of these constructions (see refs. 18a-d, 21b, 21c and literature cited therein) led to some conclusions of general importance. Thus it was established that a new phenomenon of topological chirality should be observed for compounds having the shape of trefoil knots or Mobius strips. Normally, chemists deal with chiral objects which can be (in principle) transformed into their mirror image by a continuous deformation. For... 

Fig. 18. The topologically-relevant step in the synthesis of the chiral three-rung Mobius ladder 63, starting from the linear molecular ladder 69...

A potential example of Mobius n-conjugation is the cychc cation C9H/ (212). On the basis of computational evidence provided by Schleyer et al.," it is considered a chiral Mobius 4n-7i-electron aromatic species of a helical C2-symmetrical structure with eight delocalized electrons. Allan and Rzepa" have recently explored topological homoaromaticity by analyzing a series of... 

A new aliphatic helical topology was realized with the synthesis of the first molecular Mobius-band molecule 89, which was obtained in 57 % yield from 90. The chirality of 89 was proved by the NMR method using (+)-(2,2,2)-trifluoro-9-anthrylethanol as an optically active solvent... 

For further discussion of homoaromatic systems, see (a) McEwen, A. B., Schleyer, P. v. R. (1986). In-plane aromaticity and trishomoaromaticity a computational evaluation. Journal of Organic Chemistry, 51,4357-4368. (b) Allan, C. S. M., Rzepa, H. S. (2008). Chiral Aromaticities. A Topological Exploration of Mobius Homoaromaticity. Journal of Chemical Theory and Computation, 4, 1841-1848. (c) Allan, C. S. M., Rzepa, H. S. (2008). Chiral Aromaticities. AIM and ELF Critical Point and NICS Magnetic Analyses of Mobius-Type Aromaticity and Homoaromaticity in Lemniscular Annulenes and Hexaphyrins. Journal of Organic Chemistry, 73, 6615-6622. 

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