Molecular aromaticity: a quantum phenomenon

Abstract To celebrate the International Year of Quantum Science and Technology (IYQ), we discuss how the concept of aromaticity emerges from the postulates of quantum mechanics. Based on this discussion, we analyze the case of cyclo [18]carbon, a molecule that was characterized for the first time in 2019 in a scanning tunneling microscope. From the very beginning, this molecule was classified as an aromatic molecule. In the present work, we challenge this classification and provide arguments to classify this molecule as a non-aromatic species.