Three-gold clusters form nonconventional hydrogen bonds O-H⋯Au and N-H⋯Au with formamide and formic acid

The complexes between triangle three-gold cluster and formamide and formic acid are studied within high-level density functional and MP2 approaches. The most stable ones are planar and cyclic, and formed via the Au-O anchor and N-H⋯Au or O-H⋯Au bonds for formamide and formic acid, respectively. These N-H⋯Au and O-H⋯Au bonds satisfy all the conditions required to identify conventional hydrogen bonds and can thus be treated as new, nonconventional H-bonds. Their formation is based on the cooperativity of the involved molecular interactions where the Au-O anchor bond plays a leading role. The corresponding H-bonds with Ag3 are found to be weaker.