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

Two structurally intriguing dysprosium(III)-substituted polyoxometalates, [Dy6(ampH)4(H2O)23(ampH2)(PW11O39)2] (1) and [Dy9(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 {Dy6(ampH)4} core, and a unique windmill-type {Dy9(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.