Isovalent electronic systems B+13 and BeB: structural interchange of GM and TS.

Fluxional Wankel motor molecules have received considerable attention in recent years in both chemistry and nanoscience. Based on extensive first-principles theory calculations, we present herein the smallest neutral quasi-planar alkaline-earth metal-doped Wankel motor complex BeB (BeB@B), which is isovalent with B+13 (B@B). The global minimum (GM) BeB (1) and transition state (TS) BeB (2) correspond to the TS (4) and GM (3) of B+13, respectively. Molecular dynamics simulations show that, with ten equivalent GMs and ten equivalent TSs intervals, the B outer ring in BeB (1/2) overcomes the rotational energy barrier to rotate almost freely around the BeB triangular core above 800 K in a rotation angle of 36° in each step. Detailed bonding analyses indicate that, in addition to the ten localized periphery B-B bonds, both BeB (1) and BeB (2) possess three delocalized bonding systems over the molecular framework satisfying the (4+2) Hückel rule, making the neutral complex 2σ + π triply aromatic in nature and highly stable in thermodynamics.