Abstract

When (4n +2) pi-electrons are located in single planar ring, it conventionally qualifies as aromatic. According Huckel's rule, systems possessing ten pi-electrons should be aromatic. Herein we report a series of D-5h Li6E5Li6 sandwich structures, representing the first global minima featuring ten pi-electrons E5(10-) ring (E=Si-Pb). However, these pi-electrons localize as five pi-lone-pairs rather than delocalized orbitals. The high symmetry structure achieved is a direct consequence of sigma-aromaticity, particularly favored in elements from Si to Pb, resulting in a pronounced diatropic ring current flow that contributes to the enhanced stability of these systems.