Induced Currents and Electron Counting in Aromatic Boron Wheels:  B₈^2- and B₉^-

Abstract

The newly discovered atom-centered polygonal wheels B8(2-) and B9- are predicted to show ring currents characteristic of aromatic systems. Ipsocentric mapping of induced current density for both molecules attributes a pi diatropic current to the four electrons of the doubly degenerate pi HOMO and a sigma diatropic current to the four electrons of the doubly degenerate sigma HOMO, each orbital pair having an available transition to corresponding LUMO orbitals in which the angular node count increases by one. Thus, on the magnetic criterion, B8(2-) and B9- are each both pi- and sigma-aromatic as a consequence of the nodal properties of the frontier orbitals of the pi- and sigma-stacks.

Experimental and computational evidence of octa- and nona-coordinated planar iron-doped boron clusters: Fe©B8− and Fe©B9−

“…The doubly aromatic character and the multi-center electron delocalization were confirmed by ring current calculations [18] and Adaptive Natural Density Partitioning (AdNDP) [19,20] analyses. Pure all-boron clusters have been proposed as novel building blocks of solid materials [21], and recently a remarkable Ti 7 Rh 4 Ir 2 B 8 compound containing planar B 6 ring has been synthesized [22,23].…”

Calculations of magnetically induced current densities: theory and applications

“…After the prediction of the boron centered B 8 2− and B 9 − rings by Schleyer et al and first experimental evidence for the existence of the boron centered planar boron ring anions was reported . Fowler and Gray analyzed the magnetic response properties in terms of MO contributions to the magnetically induced current densities . Strong diamagnetic responses were found for the σ and π orbitals involving mainly four electrons.…”

B19−: An Aromatic Wankel Motor

“…, B 9 À , B 10 , B 11 À , B 12 , and B 13 + boron clusters can be considered as all-boron analogues of benzene. [3][4][5][6][7] However, B 19 À is different, even when concentric p systems have been reported in organic chemistry before, none has exactly this electronic configuration.…”