Hydrogen Bonding, π-Stacking, and Aurophilic Interactions in Two Dicyanoaurate(I)-Based Manganese(II) Complexes with Auxiliary Bis-Pyridine Ligands.

The relevance of hydrogen-bonding, π-π stacking and aurophilic interactions in the solid-state of two new heterobimetallic (Au I -Mn II ) complexes is analyzed in this manuscript. They are discrete complexes of formulae [Mn(bipy) 2 (H 2 O){Au(CN) 2 }][Au(CN) 2 ] and [Mn(dmbipy) 2 {Au(CN) 2 }] ⋅ H 2 O, (bipy=2,2'-bipyridine and dmbipy=5,5'-dimethyl-2,2'-bipyridine), which are based on dicyanidoaurate(I) groups and 2,2'-bipyridyl-like co-ligands. They have been synthesized in good yields and X-ray characterized. In both compounds, aurophilic, OH⋅⋅⋅N hydrogen bonding and π-π interactions governed the supramolecular assemblies in the solid state. These contacts with special emphasis on the aurophilic interactions have been studied using density functional theory calculations and characterized using the quantum theory of atoms-in-molecules and the noncovalent interaction plot. The aurophilic contacts have been also rationalized from an orbital point of view using the natural bond orbital methodology, evidencing stabilization energies up to 5.7 kcal/mol. Moreover, the interaction energies have been decomposed using the Kitaura-Morokuma energy decomposition analysis, confirming the importance of electrostatic and orbital effects.