Communications: Tin cluster anions (Snn-, n=18, 20, 23, and 25) comprise dimers of stable subunits

The gas phase structures of tin cluster anions Sn-n(-) have been studied by a combination of trapped ion electron diffraction and density functional theory calculations. In the size range of n=18-25 these clusters comprise dimers of stable subunits. In particular Sn-18(-) and Sn-20(-) are homodimers of Sn-9 and Sn-10 subunits, respectively. In Sn-23(-) two Sn-10 units are linked by three additional bridging atoms and Sn-25(-) is a heterodimer of Sn-10 and Sn-15 subunits. This rather unexpected growth mode is rationalized by the extraordinary stability of the building blocks Sn-9, Sn-10, and Sn-15. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3442411]