Reactions of lanthanide perchlorates and manganese acetate with Schiff-base ligand (H(4)L = 2-(((2-hydroxy-3-methoxyphenyl)methylene)amino)-2-(hydroxymethyl)-1,3-propanediol) in methanol in the presence of triethylamine yielded two hexanuclear heterometallic clusters of general formula [Mn(4)(ΙΙΙ)Ln(2)(ΙΙΙ)(H(2)L)(2)(HL)(2)(CH(3)COO)(4)(CH(3)O)(2)(CH(3)OH)(4)](ClO(4))(2)·6CH(3)OH [Ln = La(ΙΙΙ) (1), Nd(ΙΙΙ) (2)]. 1 and 2 are isostructural, with the metal centres consisting of a nonplanar [Mn(4)(ΙΙΙ)Ln(2)(ΙΙΙ)(μ(2)-O)(8)(μ(3)-OR)(2)](8+) core. Variable-temperature solid state magnetic susceptibilities measurements of 1 and 2 in the temperature 2-300 K were performed, indicating dominant antiferromagnetic exchange interactions between the metal centres in both compounds. Alternating current (ac) susceptibility data for 2 displays out-of-phase signal suggesting slow relaxation of magnetization whereas no out-of-phase signal is observed in 1, highlighting the incorporation of lighter lanthanide leads to SMM property.