Photoelectron Spectroscopic and Theoretical Study of B-16(-) and B-16(2-): An All-Boron Naphthalene

Although boron clusters were experimentally studied shortly after the discovery of the fullerenes, their structural characterization was only possible fairly recently when we combined photoelectron spectroscopy (PES) and theoretical calculations to investigate the structures and bonding of boron clusters. Early theoretical studies indicated that small boron clusters do not assume cage-like structures, which are common in bulk boron and compounds; instead, planar or quasi-planar structures were suggested. The combined PES and theoretical studies show indeed boron clusters with up to 15 atom are planar, and only at B20 does a three-dimensional (3D) structure (double ring) become energetically competitive, whereas B20- still remains planar. A recent ion mobility and theoretical study showed that for Bn + the doublering 3D structure becomes competitive at B16 +7.