Quantum chemical calculations have been performed to study the interaction in H2O-AuCH3 complex. The results show that there is an Au-bonding interaction in the complex. The F substitution in the Au donor molecule enhances this interaction and the methyl group in the Au acceptor molecule also makes it enhance. The F atoms in the Au donor show a positive non-additivity, whereas the methyl groups in the Au acceptor exhibit a negative non-additivity. The Au-bonding is similar to H-bonding, but charge transfer has a greater contribution in this interaction and it exhibits partially covalent nature. (C) 2010 Elsevier B.V. All rights reserved.