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

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.