A mono-potassium cation-encapsulated Preyssler-type phosphotungstate, [P 5 W 30 O 110 K] 14– ( 1 ), was prepared as a potassium salt, K 14 [P 5 W 30 O 110 K] ( 1a ), by heating mono-bismuth- or mono-calcium-encapsulated Preyssler-type phosphotungstates (K 12 [P 5 W 30 O 110 Bi(H 2 O)] or K 13 [P 5 W 30 O 110 Ca(H 2 O)]) in acetate buffer. Characterization of the potassium salt 1a by single-crystal X-ray structure analysis, 31 P and 183 W nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared spectroscopy, high-resolution electrospray ionization mass spectroscopy, and elemental analysis revealed that one potassium cation is encapsulated in the central cavity of the Preyssler-type phosphotungstate molecule with a formal D 5 h symmetry. Density functional theory calculations have confirmed that the potassium cation prefers the central position of the cavity over a side position, in which no water molecules are coordinated to the encapsulated potassium cation. 31 P NMR and cyclic voltammetry analyses revealed the rapid protonation–deprotonation of the oxygens in the cavity compared to that of other Preyssler-type compounds. Heating of 1a in the solid state afforded a di-K + -encapsulated compound, K 13 [P 5 W 30 O 110 K 2 ] ( 2a ), indicating that a potassium counter-cation is introduced in one of the side cavities, concomitantly displacing the internal potassium ion from the center to a second side cavity, thus providing a new method to encapsulate an additional cation in Preyssler compounds.

Thermal migration of the sodium cation in the cavity of Preyssler-type phosphotungstate is reported here. Heating of a Preyssler-type compound-[P5W30O110Na(side)(H2O)] 14--in which a sodium cation occupies one of the two side cavities, at 300°C forms a new compound-[P5W30O110Na(center)] 14--in which the sodium cation is encapsulated in the central cavity. Characterization by single crystal X-ray structure analysis, NMR technique, elemental analysis, IR, and ESI-MS confirmed the structure of the compound. The thermal displacement ellipsoid of the central sodium, estimated by the crystallographic study, is elongated along the direction perpendicular to the equatorial plane of the Preyssler molecule. These results confirmed prediction using DFT calculation by López and Poblet (ref. 21, J. Am. Chem. Soc. 2007, 129, 12244.) that the most stable site for sodium is the central cavity with a slight shift from the center of the molecule.

The heat‐driven solid‐state transformations of K salts of the Na‐encapsulated Preyssler‐type phosphotungstates, K14[P5W30O110Na(side)(H2O)] and K14[P5W30O110Na(center)], are reported herein. K14[P5W30O110Na(side)(H2O)] contains one Na+ in one of the side cavities and a coordinating H2O molecule while K14[P5W30O110Na(center)] contains one Na+ in the central cavity. The heating of K14[P5W30O110Na(side)(H2O)] produces [P5W30O110Na(center)]14–, [P5W30O110K(center)]14–, and [P5W30O110K(side)2]13–. [P5W30O110K(center)]14– and [P5W30O110K(side)2]13– contain mono‐K+ in the central cavity and di‐K+ in both side cavities, respectively. The heating of potassium salt of [P5W30O110Na(center)]14– produces [P5W30O110K(center)]14– and [P5W30O110K(side)2]13–. These results indicate that heating, at 200–500 °C, causes the migrations of Na+ and K+, without the collapse of the molecule. K14[P5W30O110Na(side)(H2O)] was successfully converted to K12Na[P5W30O110K(side)2] by repeated solid‐state heating, which was periodically interrupted by dissolution, in H2O, and drying.

We report the first Peacock-Weakley type complexes composed of mono-lacunary Keggin-type phosphotungstate, [α-PW 11 O 39 ] 7-, and Bi 3+ . The self-assembly reaction between the Keggin-type phosphotungstate and Bi 3+ in aqueous solution produced Peacock-Weakley type 2:1 ([(PW 11 O 39 ) 2 Bi] 11-, 1) and 1:1 ([PW 11 O 39 Bi] 4-, 2) complexes depending on the mixing ratio of [α-PW 11 O 39 ] 7and Bi 3+ . Studies of both complexes in solution IntroductionPolyoxometalates (POMs) are anionic clusters of W, Mo, V, and Nb with attractive properties, such as photochemical, magnetic, acidic and redox activities, that find many applications in catalysis and functionalised materials. [1] Among the wide variety of reported POMs, lacunary Keggin-type compounds have extensively been investigated owing to their capability as multidentate ligands to create new polynuclear metal oxo clusters. Since the first report by Peacock and Weakley, [2] it is well known that mono-lacunary Keggin-type and Dawson-type polyoxometalates generate 2:1 and 1:1 complexes with lanthanide and actinoid cations. In these complexes, the lacunary polyoxometalates act as tetradentate ligands. However, only a few reports exist on Bi 3+ -containing 2:1 complexes, e.g. the sandwich complexes of Bi 3+ with mono-lacunary Lindqvist-type polyoxometalates, [Bi(M 4 O 13 (OCH 3 ) 4 Mo(NX)) 2 ] 3-(M =W or Mo, X = O or [a]

A graphene oxide-based α-K6P2W18O62 (Dawson-type polyoxometalate) nanocomposite was formed by using two types of graphene oxide (GO) samples with different C/O compositions. Herein, based on the interaction of GO, polyoxometalates (POMs), and their nanocomposites with the Cs cation, quantitative data have been provided to explicate the morphology and Cs adsorption character. The morphology of the GO-POM nanocomposites was characterized by using TEM and SEM imaging. These results show that the POM particle successfully interacted above the surface of GO. The imaging also captured many small black spots on the surface of the nanocomposite after Cs adsorption. Furthermore, ICP-AES, the PXRD pattern, IR spectra, and Raman spectra all emphasized that the Cs adsorption occurred. The adsorption occurred by an aggregation process. Furthermore, the difference in the C/O ratio in each GO sample indicated that the ratio has significantly influenced the character of the GO-POM nanocomposite for the Cs adsorption. It was shown that the oxidized zone (sp2/sp3 hybrid carbon) of each nanocomposite sample was enlarged by forming the nanocomposite compared to the corresponding original GO sample. The Cs adsorption performance was also influenced after forming a composite. The present study also exhibited the fact that the sharp and intense diffractions in the PXRD were significantly reduced after the Cs adsorption. The result highlights that the interlayer distance was changed after Cs adsorption in all nanocomposite samples. This has a good correlation with the Raman spectra in which the second-order peaks changed after Cs adsorption.