Double aromaticity in the triplet ground state of Be₂©Be₆H₆: A 4π Baird and 6σ Hückel electron system.

This article focuses on the structural and bonding properties of the Be₂©Be₆H₆ complex, a star-like inorganic cluster featuring a beryllium dimer (Be₂) oriented orthogonally to a planar hexagonal Be₆H₆ ring. Characterized by D₆h symmetry and a triplet ground state, this system exhibits an ultra-short Be–Be bond length of 1.874 Å and demonstrates rare dual aromaticity: six delocalized σ electrons following the Hückel 4n + 2 rule and four delocalized π electrons adhering to the Baird 4n rule. The stability of Be₂©Be₆H₆ arises from covalent dative interactions between the s/p orbitals of the Be₂ dimer and the delocalized electrons of the Be₆H₆ ring, supported by extensive computational analyses including energy decomposition, molecular orbital, and magnetically induced current density studies. This work expands the understanding of aromaticity by illustrating its manifestation through combined σ-Hückel and π-Baird aromaticity in an all-metal inorganic cluster.