Formation of Dianions in Helium Nanodroplets

The formation of dianions in helium nanodroplets is reported for the first time. The fullerene cluster dianions (C-60)(n)(2-) and (C-70)(n)(2-) were observed by mass spectrometry for n5 when helium droplets containing the appropriate fullerene were subjected to electron impact at approximately 22eV. A new mechanism for dianion formation is described, which involves a two-electron transfer from the metastable He- ion. As well as the prospect of studying other dianions at low temperature using helium nanodroplets, this work opens up the possibility of a wider investigation of the chemistry of He-, a new electron-donating reagent.