The tridecanuclear heterovalent mixed-metal (Mn11Gd2) complex [(Mn9Mn2Gd2III)-Mn-III-Gd-II(O)(8)(OH)(2)(O2CR)(17)(NO3)(2)(H2O)] has been obtained from the reaction of the hexanuclear compound [Mn6O2(Piv)(10)(4-Me-py)(2.5)(PivH)(1.5)] with Gd(NO3)(3)center dot 6H(2)O in CH3CN. The complex presents an unusual "bell"-shaped core with a high-spin ground state and is a new member of the high-nuclearity 3d-4f single-molecule magnets family.