Geometry and bonding of small binary boron-aluminum clusters BnAln (n = 1–7): Electron donation and interlocking aromaticity

Abstract

Binary BnAln clusters (n = 1–7) were investigated using both DFT/TPSSh and G4 calculations. B and Al atoms do not mix together but prefer to be assembled in two separated but interacting Bn and Aln components. Large electron donation from Al to B atoms induces a donor-acceptor stabilization. Planar B3Al3 is a σ aromatic compound. B4Al4 exhibits two aromatic electron flows that are interlocking in two perpendicular planes and circulate independently. The B7Al7 cluster appears as a double layer structure and this suggests formation of Bn and Aln layers in larger clusters connected by electrostatic interactions.