I only looked at this paper because the image with Saturn and the pineapple was so intriguing, but the story behind these molecules turned out to be quite interesting too.
For fullerenes (vulgo: buckyballs), there are rules governing the distribution of pentagons within the shape otherwise made of hexagons. There must be exactly 12 pentagons, to make sure the shell closes properly (and in the case of closed nanotubes, there can be any number of hexagons!), and the pentagons should be flanked by hexagons, i.e. no two pentagons should share an edge.
In chemistry, such rules are an open invitation for clever synthetic chemists to try and break them. The saturn- and pineapple shaped molecules are in fact two successful breakers of the pentagon rule, where the chlorine atoms sticking out from the roundish shape help to compensate for the instability produced by the "wrong" geometry.
The relevant paper by Xiao Han et al. is in Angewandte Chemie Int. Ed.
Published Online: Jun 11 2008