Synthesis and characterization of a new Hervé-type tungstoantimonite based on α-[SbW9O33]9− unit

A sandwich-type polyoxotungstate, {[Na(H2O)2]H8[KNa2(H2O)6][Cu(H2O)]3(SbW9-O33)2}n⋅4nH2O⋅4n(tn) (1) (tn = 1,3-Propanediamine) has been synthesized and characterized by IR, UV-DRS, single-crystal X-ray diffraction analysis, TGA, XPS, magnetic-dependent 2D-IR correlation spectroscopy (2D-COS IR). The Hervé-type polyanion {[KNa2(H2O)6][Cu(H2O)]3(SbW9O33)2}9− of compound 1 consists of two trivacant Keggin moieties [SbW9O33]9− which are linked by three Cu2+ ions, and the space between the three Cu2+ ions is occupied by two sodium ions and one potassium ion forming a six-membered ring, and resulting in the polyanion with C2v symmetry. Compound 1 exhibits a 1D ribbon-like structure in which the adjacent polyanions were connected by the K+ in the central belt and Na+, which is rarely reported for Hervé-type polyanion. The magnetic-dependent 2D-IR correlation spectroscopy display obvious magnetic response signal of the groups which Cu2+ ions attached to.