Unrestricted density functional calculations have revealed spin-polarized electronic structures of a charged gold-thiolate cluster [Au-25(SCH3)(18)](n) with a core-in-cage structure [Au-7-(AuSCH3)(18)]. The charged states vary from 3- to 3+. The optimized structures in the different charged states show only minor geometrical changes. For n = 2-, three parallel spins are found to be localized at the Au-7 core cluster, and hence high magnetic anisotropy is expected because the core cluster has a nearly planar geometry. These features are ascribed to a unique structure of the present gold-thiolate cluster, Au-25(SCH3)(18), that the Au-7 core cluster is protected by the robust (AuSCH3)(18) cage. (c) 2007 Elsevier B.V. All rights reserved.