The first tetranuclear metallacage and mononuclear cocrystalline Dy-III-radical complex was synthesized and characterized. The metallacage in [Dy-4(hfac)(8)(IMPhThio)(2)(OH)(4)][Dy-(hfac)(3)(NITPhThio)(2)] consists of Dy(hfac)(2)(+) groups bridged by OH- and the IMPhThio radical. Field-induced single-molecule-magnet behavior was observed in the nitronyl nitroxide radical-bridged polynuclear complex.