Interactions in coinage-metal/ligand complexes, CM–L, and their cations (CM = Cu, Ag, Au; L = CO, N₂ and H₂)

The CM–L and CM⁺–L complexes for the three coinage metals, CM = Cu, Ag and Au interacting with three key ligands, L = CO, N₂ and H₂, are investigated. Calculations are undertaken using various quantum chemical methods to ascertain the equilibrium geometries and interaction energies; the latter are calculated at the coupled-cluster level of theory, and extrapolated to the basis set limit. Some of the neutral species are found to be particularly challenging, and significant disparity is found in some cases for the geometry and/or harmonic vibrational wavenumbers. In addition, molecular orbital diagrams, atomic charges, and orbital contour plots are presented, in order to gain insight into the interactions occurring in these complexes.