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 H(2)O-AuCH(2)CH(3), H(2)O-AuCHCH(2), and H(2)O-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 H(2)O 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 T2 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···Au hydrogen bond is suggested in T1 trimer.