All-Metal Antiaromatic Molecule: Rectangular Al 4 4- in the Li 3 Al 4 - Anion

Abstract

We report the experimental and theoretical characterization of antiaromaticity in an all-metal system, Li 3 Al 4 – , which we produced by laser vaporization and studied with the use of photoelectron spectroscopy and ab initio calculations. The most stable structure of Li 3 Al 4 – found theoretically contained a rectangular Al 4 4– tetraanion stabilized by the three Li + ions in a capped octahedral arrangement. Molecular orbital analyses reveal that the rectangular Al 4 4– tetraanion has four π electrons, consistent with the 4 n Hückel rule for antiaromaticity.