Theoretical Evidence of Aromaticity in X3− (X = B, Al, Ga) Species

We investigated the electronic structure and chemical bonding of the B3−, Al3−, and Ga3− anions, and the gas phase NaB3, NaAl3, and NaGa3 molecules. We found that the ground state of the neutral gas phase salts contains an equilateral triangular anion interacting with a Na+ cation. The B3−, Al3−, and Ga3− anions possess two delocalized π electrons and are found to be aromatic. The triangular anions have been shown to be related to recently synthesized organometallic compound containing an aromatic -Ga32− unit, but they are differ from them by four valence electrons. The reason for earlier appearance of the π-orbital in the B3−, Al3−, and Ga3− anions is discussed.

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