LAUSR

Abstract The equilibrium geometries, harmonic vibrational frequencies, stabilities, and chemical bonding of the low-lying states for all-metal Hg3Al3+/−, Hg3Al3Li, and Hg3Al3Be+ clusters are investigated using 2nd order Moller–Plesset perturbation theory. The extensive search for the global minimum structures of Hg3Al3+/− at the MP2 level of theory with 6-311++G∗ basis set for Al and CEP-121 G basis set for Hg reveals that the ground states of the Hg3Al3+ and Hg3Al3− clusters are all singlet state 1A′ with Cs symmetry. A detailed molecular orbital (MO) analysis reveals that the Hg3Al3+ (Cs, 1A′) cation and Hg3Al3− (Cs, 1A′) anion possess double aromaticity (simultaneous presence of σ- and π-aromaticity). The hexagonal pyramidal-type Hg3Al3Li and Hg3Al3Be+ complexes containing the Hg3Al3− ligand reveal that the Hg3Al3− structural units are preserved in the Hg3Al3Li and Hg3Al3Be+ complexes, which also possess corresponding aromatic characters.