Hybrid density functionals and ab initio studies of 2-pyridone–H2O and 2-pyridone–(H2O)2

Theoretical calculations have been carried out on the interaction between water and the carbonyl base 2-pyridone. The calculations have been performed with two hybrid density functionals (B3-PW91 and B3-LYP). The comparison with experimental gas phase data as well as with results from the ab initio methods RHF and MP2 shows good performance of these functionals, especially for B3-LYP. Two stable structures were found for the 2-pyridone–H2O complex: the first one is a closed complex with two hydrogen bonds, CO⋯H–O⋯H–N, while the second structure is an open complex, CO⋯H–OH. The theoretical results indicate that the closed complex is the most stable one due to a cooperative effect between the two H-bonds. The structure of the 2-pyridone–(H2O)2 heterotrimer is also closed with three hydrogen bonds, CO⋯H–O⋯H–O⋯H–N.