Quantum Tunnelling Drives Aromaticity Flip-Flop
Researchers in Israel have discovered molecules that can switch between aromatic and antiaromatic structures rapidly, or even adopt both at once.
Aromatic and antiaromatic structures are two distinct personas in cyclic chemistry, with aromatics like benzene being stable and serene, and antiaromatics like pentalene being fractious and flighty.
The discovery was made while studying quantum tunnelling, a phenomenon where particles can pass through a barrier they lack the energy to surmount, which appears in many automerisation reactions.
The augmented pentalene structure could be a molecular Schrödinger's cat, aromatic and antiaromatic at the same time.
The researchers at Ben-Gurion University of the Negev and Technion-Israel Institute of Technology identified this unique behavior, which challenges the traditional understanding of cyclic chemistry.
Author's summary: Quantum tunnelling enables aromaticity flip-flop in molecules.