Syntheses, structures and magnetic properties of a family of heterometallic [MnII_2MnIII_2LnIII_2] clusters

摘要

A new family of isostructural Mn-Ln heterometallic clusters, [Mn~(II)_2Mn~(III)_2Ln~(III)_2(Piv)_8(thme)_2(H_2tea)_2] (H_3thme = 1,1,1-tris(hydroxymethyl)ethane, Hpiv = pivalic acid, H_3tea = triethanolamine, and Ln = Pr, Nd, Sm, Eu, Gd, Tb, and Dy) have been prepared by reaction of the hexanuclear manganese precursor, [Mn 6O_2(Piv)10(4-Me-Py)_(2.5)(Hpiv)_(1.5)], with H_3thme, H_3tea, and Ln(NO 3)_3·6H_2O 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)(μ3-OR)_4(μ2-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.