Dodenuclear [Mn8IIILn4III] clusters with 2-(hydroxymethyl)pyridine: syntheses, structures, and magnetic properties

A new family of isostructural Mn/Ln dodenuclear clusters: [Mn(8)Ln(4)(O)(8)(hmp)(4)(O2CPh)(2()NO3)(4)(PhCO2H)-(C2H5OH)] [Ln = La (1), Pr (2), Nd (3), Gd (4), Dy(5), hmpH = 2-(hydroxymethyl) pyridine] have been synthesized by the reaction of Mn(NO3)(2) and Ln(NO3)(3)center dot 6H(2)O with hmpH and benzoic acid as co-ligands. Compounds 1-5 possess a spindle-shaped core of [Mn(8)(III)Ln(4)(III)(mu(4)-O)(4)(mu(3)-O)(4)(mu(3)-OR)(2)(mu(2)-OR)(8)](10+), which is composed of six face-sharing defected cubane units and two square-pyramidal units. The compounds represent the highest nuclearity Mn/Ln clusters with the use of hmpH to date. That the ferromagnetic interactions dominated within complexes 1-4 were suggested by solid-state dc magnetic susceptibility analyses. Compound 4 displays a magnetic-caloric effect (MCE) with 13.94 J kg(-1) K-1 as the entropy change at 6 K for Delta H = 8 T. Compounds 1 and 5 exhibit an out-of-phase chi ''(M) peak maximum above 2.0 K. Fitting of the ac susceptibility data to an Arrhenius law gives an energy barrier U-eff = 6.88/7.44 K for compounds 1 and 5 respectively.