Syntheses, structure, and magnetic properties of hexanuclear Mn2IIIM4III (M = Y, Gd, Tb, Dy) complexes

The synthesis and characterizations of a family of isomorphous [(Mn2M4L2)-M-III-L-III(mu(4)-O)(2)(N-3)(2)(CH3O)(2)(CH3OH)(4)(NO3)(2)]center dot 2H(2)O (M = Y(1), Gd(2), Tb(3), Dy(4)) are reported, where H4L = N,N'-dihydroxyethyl-N,N'-(2-hydroxy-4,5-dimethylbenzyl)ethylenediamine. They were obtained from the reactions of H4L with M(NO3)(3)center dot 6H(2)O, Mn(ClO4)(2)center dot 6H(2)O, NaN3 and NEt3 in a 1 : 1 : 1 : 2 : 2 molar ratio. The core structure consists of a Mn2M4 unit. The four M-III ions that are held together by two mu(4)-bridging oxygen atoms form a butterfly M-4 moiety. The M-4 core is further connected to the two five-coordinate trigonal-bipyramidal Mn-III ions via one mu(4)-O2-, two alkyloxo and one methoxo triple bridges. Magnetic susceptibility measurements indicate the presence of intramolecular antiferromagnetic interactions in complex 2, and overall intramolecular ferromagnetic interactions in complexes 3 and 4. The alternating current (AC) magnetic susceptibility studies revealed that complexes 3 and 4 showed frequency-dependent out-of-phase signals, which indicates that they exhibit slow relaxation of the magnetization.