Synthesis of the first Zn6-hexagon sandwich-tungstoantimonate via rearrangement of a non-lacunary Krebs-type polyoxotungstate

Abstract

A novel synthetic pathway to obtain the first Zn₆ hexagon tungstoantimonate [(Zn(H₂O))₆(B-α-SbW₉O₃₃)₂]⁶⁻ ([Zn₆-α-SbW₉] (1)) via rearrangement of a non-lacunary Krebs-POM precursor (C₁₂N₄H₁₁)₄K₄[(Mn(H₂O)₃)₂((Mn_0.5W_0.5)O₂)₂(B-β-SbW₉O₃₃)₂] ([Mn-β-SbW₉]) has been developed. Addition of ortho-phenylenediamine (opda) in order to optimize the synthesis of [Mn-β-SbW₉] led to the crystallization of a novel Krebs-type Zn-POM (C₁₂N₄H₁₁)₄Na₅[((Zn₀.₈W_0.2)(H₂O)₃)₂((Zn_0.2W_0.8)O₂)₂(B-β-SbW₉O₃₃)₂] ([(Zn/W)₂-β-SbW₉] (2)) comprising four disordered Zn-centers after replacement of MnCl₂ with ZnCl₂. The compounds were characterized in the solid state by single-crystal and powder X-ray diffraction (XRD), IR spectroscopy, thermogravimetric analysis (TGA) and elemental analysis and in solution by UV-vis spectroscopy and ESI-mass spectrometry. The Krebs-POM archetype and the Zn₆ hexagon tungstoantimonate have been investigated towards their interactions with Human Serum Albumin (HSA) as a model protein using SDS-PAGE and trypthophan fluorescence quenching.