New Mn12 single-molecule nanomagnets [Mn12O12(O2CCHCl2)(H2O)4]·2CH2Cl2·H2O and [Mn12O12(O2CCHCl2)(H2O)4]·2CH3C6H5·4H2O and novel Mn18 complexes [M18O14(O2CR)18(hmp)4(hmpH)2(H2O)2] (R=Me, Et) have been synthesized and characterized by single crystal X-ray crystallography and dc- and ac-magnetic susceptibility measurements. Mn12 complexes show characteristic SMM properties, such as temperature-dependent out-of-phase ac-susceptibility. Mn18 does not show relaxation behaviors down to 2.0 K, but reveals magnetic anisotropy in reduced magnetization experiment.