Abstract

We investigated the electronic structure and chemical bonding of the B-3(-), Al-3(-), and Ga-3(-) 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 B-3(-), Al-3(-), and Ga-3(-) anions possess two delocalized pi electrons and are found to be aromatic. The triangular anions have been shown to be related to recently synthesized organometallic compound containing an aromatic -Ga-3(2)- unit, but they are differ from them by four valence electrons. The reason for earlier appearance of the pi-orbital in the B-3(-), Al-3(-), and Ga-3(-) anions is discussed.