A family of novel Mn3Ln4 clusters displaying single-molecule magnet behavior

Using 3-methyloxysalicylaldoxime (mosaoH(2)) and N-methyl diethanolamine (N-mdeaH(2)) as coligands, a family of heptanuclear Mn/Ln heterometallic compounds [Mn(II)Mn(2)(III)Ln(4)(III)(mosao)(2)(mosaoH)(4)(piv)(4)(N-mdea)(4)]center dot xMeCN [Ln = Dy(1), Tb(2) and Y(3), pivH = pivalic acid] have been prepared. The crystal structures of 1-3 were obtained, and their core consists of two Mn(III)Ln(2)(mu(3)-OR)(2) (RO2- = N-mdea(2-)) triangles linked to a central Mn-II atom. A dc magnetic susceptibility study reveals that single-ion effects of the Ln ions are dominant in compounds 1 and 2. As for compound 3, which contains diamagnetic Y ions, the magnetic interactions between Mn ions via oximate NO bridges are revealed to be ferromagnetic. Fitting of the chi T-m vs. T data gives g = 1.96 and J = 1.12 cm(-1), affording a S = 13/2 ground state. All of the three compounds exhibit frequency-dependent out-of-phase ac susceptibility signals indicative of slow magnetization relaxation and potential SMM behavior. Among them, 1 and 3 display the out-of-phase chi ''(m) peak maximum above 2.0 K. Fitting of the ac susceptibility data to the Arrhenius law gives an energy barrier U-eff = 9.27/13.83 K for 1 and 3, respectively.