Synthesis of the first Zn(6)-hexagon sandwich-tungstoantimonate via rearrangement of a non-lacunary Krebs-type polyoxotungstate

A novel synthetic pathway to obtain the first Zn(6) hexagon tungstoantimonate [(Zn(H(2)O))(6)(B-α-SbW(9)O(33))(2)](6–) ([Zn(6)-α-SbW(9)] (1)) via rearrangement of a non-lacunary Krebs-POM precursor (C(12)N(4)H(11))(4)K(4)[(Mn(H(2)O)(3))(2)((Mn(0.5)W(0.5))O(2))(2)(B-β-SbW(9)O(33))(2)] ([Mn-β-SbW(9)]) has been developed. Addition of ortho-phenylenediamine (opda) in order to optimize the synthesis of [Mn-β-SbW(9)] led to the crystallization of a novel Krebs-type Zn-POM (C(12)N(4)H(11))(4)Na(5)[((Zn(0).(8)W(0.2))(H(2)O)(3))(2)((Zn(0.2)W(0.8))O(2))(2)(B-β-SbW(9)O(33))(2)] ([(Zn/W)(2)-β-SbW(9)] (2)) comprising four disordered Zn-centers after replacement of MnCl(2) with ZnCl(2). 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 Zn(6) hexagon tungstoantimonate have been investigated towards their interactions with Human Serum Albumin (HSA) as a model protein using SDS-PAGE and trypthophan fluorescence quenching.