Density　functional　theory　(DFT)　and　coupled　cluster　theory　(CCSD(T))　calculations　are　carried　out　to　investigate　the　electronic　and　structural　properties　of　a　series　of　bimetallic　oxide　clusters　MW2O9-/0　(M　=　V,　Nb,　Ta).　Generalized　Koopmans＇　theorem　is　applied　to　predict　the　vertical　detachment　energies　(VDEs)　and　simulate　the　photoelectron　spectra　(PES).　Theoretical　calculations　at　the　B3LYP　level　yield　singlet　and　doublet　ground　states　for　the　bimetallic　anionic　and　neutral　clusters,　respectively.　All　the　clusters　present　the　six-membered　ring　structures　with　different　symmetries,　except　that　the　TaW2O9-　cluster　shows　a　chained　style　with　a　penta-coordinated　tantalum　atom.　Spin　density　analyses　reveal　oxygen　radical　species　in　all　neutral　clusters,　consistent　with　their　structural　characteristics.　Moreover,　additional　calculations　are　performed　to　study　the　oxidation　reaction　of　CO　molecule　with　the　W3O9+　cation　and　the　isoelectronic　VW2O9　cluster,　and　results　indicate　that　the　introduction　of　vanadium　at　tungsten　site　can　efficiently　improve　the　oxidation　reactivity.　(C)　2013　Elsevier　B.V.　All　rights　reserved.