Two New Extended Frameworks Constructed from the Sandwiching Polytungstoantimonate Clusters

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

For the first time, the Krebs-POM archetype was used as a non-lacunary precursor expanding the rarely reported hexagon sandwich-POM family.

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.

Synthesis, crystal structure and properties of sandwich type compounds based on {AsW9} and a hexa-nuclear unit with three supporting TM–triazole complexes

Tree {AsW₉}-based sandwich compounds exhibit good electrocatalytic activity, antiferromagnetic interactions, and inhibitory effect on proliferation of HeLa cells.

Functionalization of Krebs-type polyoxometalates with N,O-chelating ligands: a systematic study

The first organic derivatives of 3d-metal-disubstituted Krebs-type polyoxometalates have been synthesized under mild bench conditions via straightforward replacement of labile aqua ligands with N,O-chelating planar anions on either preformed or in situ-generated precursors. Nine hybrid clusters containing carboxylate derivatives of five- or six-membered aromatic N-heterocycles as antenna ligands have been obtained as pure crystalline phases and characterized by elemental and thermal analyses, infrared spectroscopy, and single-crystal X-ray diffraction. They all show the general formula [{M(II)L(H2O)}2(WO2)2(B-β-XW9O33)2](n-) and can be classified as follows: 1-SbM, where L = 1H-imidazole-4-carboxylate (imc), X = Sb(III), n = 12, and M(II) = Mn, Co, Ni, Zn; 1-TeM, where L = imc, X = Te(IV), n = 10, and M(II) = Mn, Co; 2-SbNi, where L = 1H-pyrazole-3-carboxylate (pzc), X = Sb(III), n = 12, and M(II) = Ni; and 3-SbM, where L = pyrazine-2-carboxylate (pyzc), X =Sb(III), n = 12, and M(II) = Co, Zn. The 3d-metal-disubstituted tungstotellurate(IV) skeleton of compounds 1-TeM is unprecedented in polyoxometalate chemistry. The stability of these hybrid Krebs-type species in aqueous solution has been confirmed by (1)H NMR spectroscopy performed on the diamagnetic 1-SbZn and 3-SbZn derivatives. Our systematic study of the reactivity of disubtituted Krebs-type polyoxotungstates toward diazole-, pyridine-, and diazinecarboxylates demonstrates that organic derivatization is strongly dependent on the nature of the ligand, as follows: imc displays a "universal ligand" character, as functionalization takes place regardless of the external 3d metal and heteroatom; pzc and pyzc show selectivity toward specific 3d metals; pyridazine-3-carboxylate and pyrimidine-4-carboxylate promote partial decomposition of specific precursors, leading to [M(II)L2(H2O)2] complexes; and picolinate is inert under all conditions tested.