Syntheses, structures and magnetic properties of a family of heterometallic [MnII2MnIII2LnIII2] clusters

A new family of isostructural Mn-Ln heterometallic clusters, [Mn(2)(II)Mn(2)(III)Ln(2)(III)(Piv)(8)(thme)(2)(H(2)tea)(2)] (H(3)thme = 1,1,1-tris(hydroxymethyl)ethane, Hpiv = pivalic acid, H(3)tea = triethanolamine, and Ln = Pr, Nd, Sm, Eu, Gd, Tb, and Dy) have been prepared by reaction of the hexanuclear manganese precursor, [Mn6O2(Piv)(10)(4-Me-Py)(2.5)(Hpiv)(1.5)], with H(3)thme, H(3)tea, and Ln(NO3)(3)center dot 6H(2)O under the solvothermal conditions. Complexes 1Pr-7Dy were characterized by single-crystal X-ray diffraction and their core [Mn-2(III)-Mn(2)(II)Ln(2)(III)(mu(3)-OR)(4)(mu(2)-OR)(6)](6+) composed of four face-sharing defected cubane units. Antiferromagnetic (AF) exchange interactions were suggested for all of the complexes by solid-state dc magnetic susceptibility measurements. Complexes 6Tb and 7Dy, show frequency-dependent ac susceptibility signals suggestive of slow magnetic relaxation.