pH-Controlled Assembly of Organophosphonate-Bridged Dysprosium(III) Single-Molecule Magnets Based on Polyoxometalates

Two structurally intriguing dysprosium(III)-substituted polyoxometalates, [Dy-6(ampH)(4)(H2O)(23)(ampH(2))(PW11O39)(2)] (1) and [Dy-9(CO3)(3)(ampH)(2)(H2O)(12)(PW10O37)(6)](35-)(2), are assembled by the same precursor under different pH conditions. The structure of 1 contains an octahedral {Dy-6(ampH)(4)} core, and a unique windmill-type {Dy-9(CO3)(3)(ampH)(2)} for 2. Single-molecule magnet behavior is observed for 2 with a thermally activated energy barrier of 56 K and no appreciable quantum tunneling of magnetization under zero field.