Planar graphs, topological chirality

In short, the absence of rigidly achiral presentations, planar or otherwise, is a necessary condition for the topological chirality of a molecular graph. Yet, as we shall later see, it is still not a sufficient one. 

Another topologically chiral K5 molecule is the chiral ferrocenophane ketone derivative 51 (Fig. 8), which is an intermediate in the synthesis of tetrabridged ferrocenophanes [79]. It is important to notice that in order to obtain a non-planar molecular graph, at least four of the ten Fe —C bonds must be taken into account. The K5 subgraph (52) also contains an oriented edge ( —CH2CH2CH2CO-fragment) and a coloured vertex (Fe atom). 

At the time they were synthesized, these molecules were not recognized as having a non-planar graph, and actually the first topologically chiral K5 molecule recognized as such, is the centered polyquinane derivative 53, independently synthesized by H. E. Simmons and J. E. Maggio [80] on the one hand, and by L. A. Paquette and M. Vazeux [81] on the other hand (Fig. 9). That it is topologi-... 

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