Influence of Hybridization and Cooperativity on the Properties of Au-Bonding Interaction: Comparison with Hydrogen Bonds

Quantum chemical calculations have been performed to study the hybridization effect in H2O-AuCH2CH3, H2O-AuCHCH2, and H2O-AuCCH dimers, and the cooperativity between the hydrogen bond and Au bonding in three trimers (T1, T2, and T3) composed of one AuCCH and two H2O molecules. With regard to the organic Au compounds, sp-hybridized AuCCH forms the strongest Au bonding, followed by sp(2) and then sp(3). The C-Au bond is elongated, and its elongation becomes larger with the increase of the s character in hybrid orbitals, whereas the corresponding stretch vibration displays a small blue shift. The positive cooperativity is present for the hydrogen bond and Au bonding in T1 and T trimers, whereas the negative cooperativity is found in T3 trimer. The results show that the hybridization effect and cooperative interaction in Au bonding are similar to those in hydrogen bonds. Additionally, an OH center dot center dot center dot Au hydrogen bond is suggested in T1 trimer.