A Heptacobalt(II/III) dicubane cluster with polyoxometalate and acetato ligands: synthesis, crystal structure, and magnetic properties

The new polyoxometalate [Co7(OH)6(H2O)2(CH3COO)4(PW9O34)2]13− (1) has been synthesized and characterized by IR, UV-Vis-NIR, TGA-TDA, X-ray single crystal analysis, and magnetic studies; 1 consists of two trilacunary heptadentate B-α-[PW9O34]9− ligands encapsulating a heptacobalt dicubane-like {CoII6CoIIIO8} core, in which the Co2+ ions are further coordinated by two water molecules and four acetate anions acting as monodentate ligands. The magnetic properties of 1 have been fitted according to an anisotropic exchange model in the low-temperature regime and discussed on the basis of ferromagnetic interactions between Co2+ ions with angles Co-L-Co (L = O, OH) close to orthogonality and weakly antiferromagnetic interactions between Co2+ ions connected through a central diamagnetic Co3+ ion.