The partial oxidation reaction of ethylene on neutral and anionic Ag-7 clusters has been studied using the BPW91 hybrid DFT method with the Stuttgart RSC97 relativistic pseudopotential for the 28-electron ionic core of Ag. The atomic oxygen reaction mechanism is mainly addressed. Results show that the reaction occurs via a stable oxametallacycle intermediate (Ag7OC,H-4(P), p = 0 or -1), but it involves small reaction barriers along the reaction path. The ZPE-corrected barrier heights are obtained as 0.7-6.5 kcal/mole. In addition, the structure and anionic effects of Ag-7 clusters are also discussed. (c) 2006 Elsevier B.V. All rights reserved.