The B40 anion

14 July 2014 - Chemical Zoo

B40.PNGThe same people that brought you the B30 anion just a month ago, now report the B40 anion. This time the popular science press jumped on the news because this anion is not just flat with an hexagonal hole in it (as was the B30 anion) but a cage-like molecule very much like fullerene. The researchers used the same recipe: construct a great many B40 isomers on a computer, simulate their photoelectron spectra, then create a gas of boron clusters, separate by mass in a mass spectrometer, capture each fraction by photoelectron spectroscopy and wait patiently for B40 to fly by. Of course the claim hinges a lot on spectrum gazing and on first glance both spectra (one experimental and one computed) on the left do not even remotely resemble each other. It is more complicated than that, more than one isomer is at play and relative energies have to be taken into consideration. The anion is described as box-shaped (D2d symmetry) with one hexagonal hole and one heptagonal hole. It already has a dedicate Wikipedia page called borospherene.
Note to popular press readers: in contrast to neutral fullerene this molecule is charged, it has only been detected in tiny amounts in a gas and it is also not possible to order it by the bottle.