Synthesis, crystal structure and magnetic properties of an enneanuclear manganese cluster containing mixed chelating ligands

A new mixed-valence [Mn₉] cluster of formulae [Mn₉O(OH)₃Cl₄(N₃)₃(hmp)₆(dpkd)₃]·1.5CH₃CN·3H₂O (1·1.5CH₃CN·3H₂O, where hmp⁻ and dpkd²⁻ are the anion of 2-hydroxymethylpyridine and the dianion of the gem-diol form of the dpk, respectively) has been synthesized and characterized by single-crystal X-ray diffraction, IR spectra, elemental analysis and magnetic measurements. Single-crystal structural analysis shows that complex 1 contains a [Mn₉] core with a new structural topology in the Mn clusters, in which the centered six Mn^III atoms compose a trigonal antiprism and the peripheral residual three Mn^II atoms can be seen as the skirt hem of this antiprism. DC magnetic susceptibility studies indicate that the overall antiferromagnetic interactions between Mn ions are present in the cluster. Fitting the data of magnetization and extrapolation of the χ_M′T suggest the spin ground states of S = 3.5, and no out-of-phase (χ_M″) signals are present in the alternating current (AC) susceptibility.