Structural, bonding, and superhalogen properties of Au4X4-/0 (X = F, Cl, Br, and I) clusters

The structural, bonding, and superhalogen properties of Au4X4-/0 (X = F, Cl, Br, and I) clusters were investigated by density functional theory calculations. Our results found that Au4F4-, Au4Cl4-, and Au4Br4- have similar cyclic arrangements, spectral, and superhalogen features, and Au4I4- has a D4h symmetric planar ring-like structure, while Au4X4 neutrals all adopt a D-2d symmetric quasi-planar eight-membered ring. Bond lengths, Wiberg bond orders, molecular orbital, ELF, and PDOS analyses suggest that the Au-I and Au-Au bonding in Au4X4-/0 are weak involving both covalent and ionic contributions. The nucleus-independent chemical shift, aromatic stabilization energy, and multicenter bond index calculations suggest that Au4I4- has significant aromaticity.