Room-temperature reactions of N,N,N ',N '-tetrakis(2-hydroxyethyl)-ethylenediamine with manganese(II) salts yield a novel family of Mn-12 clusters incorporating the same Mn12O4 core and tunable oxidation states of (MnxMn12-xII)-Mn-III (x = 8, 10, and 12). Magnetic susceptibility data indicate that the spin of the ground state increases as the number of Mn-III ions is increased, leading to increases in the magnitude of the out-of-phase ac susceptibility signal as the number of Mn-III ions is increased.