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 IL-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 BS-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. (C) 2000 Elsevier Science B.V. All rights reserved.