Electron density properties and metallophilic interactions of coinage metal halides M2X2 (M = Cu, Ag and Au, X = F-I): Ab initio calculation

Systematic theoretical investigations have been performed to understand the periodicity, structures, and interactions of the coinage metal halide series, M2X2 (M = Cu, Ag and Au, X = F-I). Mechanisms of M-X and M-M interactions were investigated by natural bond orbital analyses, natural resonance theory, electron localization function, electron density deformation, and atoms in molecules theory, and visualized by reduced density gradient analyses. Periodic trends are found in the bond length, stability, and covalent nature of the M-X and M-M interactions. As expected, Au-Au and Au-X interactions contain enhanced and increased covalence when halogens become heavier.