Pseudohalogens as Building Blocks of Hyperhalogens: A Case Study with Au(CN)$_{x}$ Complexes

Electron affinity (EA) is one of the major factors that govern reactivity. Halogen atoms possess the highest electron affinities among the elements in the periodic table since it takes only one electron to close their shell. Pseudohalogens also require one electron to close their shell and thus mimic the properties of halogens. A typical example is the CN moiety whose electron affinity (3.8 eV) is slightly larger than that of Cl. Using calculations based on density functional theory we show that when a Au atom is surrounded by CN moieties, the electron affinity of Au(CN)$_{x}$ complexes rise above that of CN for x$\ge $2 and reach a value as high as 8.4 eV, thus forming hyperhalogens. Electron affinities also show odd even alternation with the clusters with even x having higher EA values. Equilibrium geometries, electronic structure and spectroscopic properties of these complexes will be presented and results will be compared with available experimental data.