Herein we propose a general mechanism for the racemization of [n]helicenes up to n = 24. It is a concerted process for n = 4–7, but a multi-step mechanism is followed for n ≥ 8, involving 2n − 14 intermediates. The changes in the barriers are a delicate consequence of the steric hindrance and the π-interactions.

Would it be possible to eventually derive a simple methodology to predict the structure adopted by boron clusters based on its structural transformation induced by the doping with one or two metal atoms?

Among the list of planar tetracoordinate atoms, fluorine is missing. So far, there are no theoretical or experimental reports suggesting their existence. Herein, we introduce the first six combinations (FIn₄ ⁺, FTl₄ ⁺, FGaIn₃ ⁺, FIn₂Tl₂ ⁺, FIn₃Tl⁺, and FInTl₃ ⁺) whose global minima contain a planar tetracoordinate fluorine. The bonding analyses indicate that the interactions between the fluorine and the peripheral atoms are significantly electrostatic, which is also reflected in the electronic delocalization. As opposed to other planar tetracoordinate systems with carbon, nitrogen, or oxygen atoms, the fluorine in the ptFs does not act as a σ-acceptor, restraining any back-donation. On the other hand, σ-electrons show a diatropic response, which would characterize these clusters as σ-aromatic.

An unexpected tubular-shaped MgB ₁₈ cluster is identified for the first time in alkaline-earth metal-doped boron clusters.