The p-electrons in benzene, the quintessential aromatic molecule, were previously shown to be distortive, i.e., they prefer localized double bonds alternating with single bonds. It is the s-electrons that force the double bonds to delocalize, leading to a regular, D 6h geometry. Herein, we computationally investigate the double-bond localizing or delocalizing propensities of sand p-electrons in the archetypal all-metal aromatic cluster Al 4 2À and its second-and fourth-period analogs B 4 2À and

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... Ga 4 2À , using Kohn-Sham molecular orbital (MO) theory at BP86/TZ2P in combination with quantitative bond energy decomposition analyses (EDA). We compare the three all-metal aromatic clusters with the structurally related organic species C 4 H 4 2+ , C 4 H 4 , and C 4 H 4 2À . Our analyses reveal that the p-electrons in the group-13 M 4 2À molecules have a weak preference for localizing the double bonds. Instead, the s-electrons enforce the regular D 4h equilibrium geometry with delocalized double bonds.