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A synthesis of five reduced polyoxomolybdate anions is presented. The use of IR spectroscopy, hydrothermal reactions and redox titrations is described.

Polyoxothiometalate ions (ThioPOM) are active hydrogen‐evolution reaction (HER) catalysts based on modular assembly built from electrophilic clusters {MoSx} and vacant polyoxotungstates. Herein, the dumbbell‐like anion [{(PW11O39)Mo3S4(H2O)3(OH)}2]8− exhibits very high light‐driven HER activity, while the active cores {Mo3S4} do not contain any exposed disulfido ligands, which were suspected to be the origin of the HER activity. Moreover, in the catalyst architecture, the two central {Mo3S4} cores are sandwiched by two {PW11O39}7− subunits that act as oxidant‐resistant protecting groups and behave as electron‐collecting units. A detailed photophysical study was carried out confirming the reductive quenching mechanism of the photosensitizer [Ir(ppy)2(dtbbpy)]+ by the sacrificial donor triethanolamine (TEOA) and highlighting the very high rate constant of the electron transfer from the reduced photosensitizer to the ThioPOM catalyst. Such results provide new insights into the field of molecular catalytic systems able to promote high HER activity. [ABSTRACT FROM AUTHOR]

The redox parameters of the Keggin anions alpha-(SiMo3-xVxW9O40)(4+x)- and alpha-(PMo3-xVxW9O40)(3+x)-, with X = 1, 2, or 3, are presented. The one-electron-reduced species were prepared by electrolysis and characterized by ESR spectroscopy both in solution and solid state. The results showed that the ESO spectra of the V4+ ion is dependent on the surrounding atoms, Mo(V)I, W(VI) and V(V). The electron hopping and delocalization characteristics of di and trivanadium compounds were also determined.

Alpha-(SiMo2W10O40)4-, alpha-(SiMo3W9O40)4- and alpha-(SiMo2VW9O40)5- were yielded from the anion alpha-(SiW9O34)10- by a synthetic route through the monovacant anion alpha-(SiMo2W9O39)8-. The NMR study of the Keggin heteropolytungstates showed homonuclear 2J(sub W-O-W) coupling constants in the range 21-22 Hz for corner coupling and 5-7 Hz for edge coupling. The compounds with metallic vacancies revealed a wider distribution of coupling constant values.

We report on the synthesis, structure, and physicochemical characterization of the first three examples of neutral palladium‐oxo clusters (POCs). The 16‐palladium(II)‐oxo cluster [Pd16O24(OH)8((CH3)2As)8] (Pd16) comprises a cyclic palladium‐oxo unit capped by eight dimethylarsinate groups. The chloro‐derivative [Pd16Na2O26(OH)3 Cl3 ((CH3)2 As)8] (Pd16Cl) was also prepared, which forms a highly stable 3D supramolecular lattice via strong intermolecular interactions. The 24‐palladium(II)‐oxo cluster [Pd24O44(OH)8((CH3)2As)16] (Pd24) can be considered as a bicapped derivative of Pd16 with a tetra‐palladium‐oxo unit grafted on either side. The three compounds were fully characterized 1) in the solid state by single‐crystal and powder XRD, IR, TGA, and solid‐state 1H and 13C NMR spectroscopy, 2) in solution by 1H, 13C NMR and 1H DOSY spectroscopic methods, and 3) in the gas phase by electrospray ionization mass spectrometry (ESI‐MS). [ABSTRACT FROM AUTHOR]

We report on the synthesis, structure, and physicochemical characterization of the first three examples of neutral palladium‐oxo clusters (POCs). The 16‐palladium(II)‐oxo cluster [Pd16O24(OH)8((CH3)2As)8] (Pd16) comprises a cyclic palladium‐oxo unit capped by eight dimethylarsinate groups. The chloro‐derivative [Pd16Na2O26(OH)3 Cl3 ((CH3)2 As)8] (Pd16Cl) was also prepared, which forms a highly stable 3D supramolecular lattice via strong intermolecular interactions. The 24‐palladium(II)‐oxo cluster [Pd24O44(OH)8((CH3)2As)16] (Pd24) can be considered as a bicapped derivative of Pd16 with a tetra‐palladium‐oxo unit grafted on either side. The three compounds were fully characterized 1) in the solid state by single‐crystal and powder XRD, IR, TGA, and solid‐state 1H and 13C NMR spectroscopy, 2) in solution by 1H, 13C NMR and 1H DOSY spectroscopic methods, and 3) in the gas phase by electrospray ionization mass spectrometry (ESI‐MS). [ABSTRACT FROM AUTHOR]

Herein, we report the synthesis of N-tert-butoxycarbonyl (BOC) protected [V6O13{(OCH2)3C–NH2}2]2− built from the Lindqvist-type hexavanadate. The reaction of di-tert-butyl dicarbonate (BOC2O) with tris(hydroxymethyl)aminomethane (Tris) led to the organic derivative [(OCH2)3C–NH(BOC)] that reacts with the decavanadate in dimethylacetamide (DMA) to form the [V6O13{(OCH2)3 C–NH(BOC)}2]2− anion. The tetrabutylammonium (TBA+) salt of this hybrid polyoxovanadate, TBA2[V6O13{(OCH2)3C–NH(BOC)}2]· 2DMA, has been characterized in the solid-state by single-crystal X-ray diffraction and infrared spectroscopy, and in solution by multinuclear (1H, 13C, 15N and 51V) and DOSY NMR, and UV–visible spectroscopy. [ABSTRACT FROM AUTHOR]

Specific molecular recognition of γ‐cyclodextrin (γ‐CD) by the cationic hexanuclear niobium [Nb6Cl12(H2O)6]2+ cluster complex in aqueous solutions results in a 1:1 supramolecular assembly {[Nb6Cl12(H2O)6]@γ‐CD}2+. NMR spectroscopy, isothermal titration calorimetry (ITC), and ESI‐MS were used to study the interaction between the inorganic cluster and the organic macrocycle. Such molecular association affects the biological activity of [Nb6Cl12(H2O)6]2+, decreasing its cytotoxicity despite enhanced cellular uptake. The 1:1 stoichiometry is maintained in solution over a large window of the reagents' ratio, but crystallization by slow evaporation produces a 1:2 host–guest complex [Nb6Cl12(H2O)6@(γ‐CD)2]Cl2⋅20 H2O featuring the cluster encapsulated between two molecules of γ‐CD. The 1:2 complex was characterized by XRD, elemental analysis, IR spectroscopy, and thermogravimetric analysis (TGA). Quantum chemical calculations were performed to model host–guest interaction. [ABSTRACT FROM AUTHOR]

X-ray diffraction analysis has shown the presence of the targeted molecular compound, which has the {[Mo.sub.18][O.sub.18][S.sub.18][(OH).sub.18]} host templated by the [[[Mo.sub.3][S.sub.4][(Hnta).sub.3]].sup.sup 2-] guest, and the structure has shown an additional molecular moiety corresponding to a dinuclear unit {[Mo.sub.2][O.sub.2][S.sub.2]}. The dinuclear individual species in solution has given rise to cis-trans equilibrium, while in the presence of the oxothiomolybdenum ring the dinuclear unit is maintained as a frozen cis complex.

The Stokes-Einstein expression of the diffusion coefficient as a function of the hydrodynamic radius of the diffusing object has not carried the mass dependency of the object, but the translational self-diffusion coefficients D are correlated with the molecular weight M for an ensemble of cyclic or hollow clusters. The correlation has shown that the mass of a cluster is deduced from its diffusion coefficient.

The synthesis and structural characterization of the two polyanions, [[([alpha]-[Ti.sub.3]P[W.sub.9][O.sub.38]).sub.3](P[O.sub.4])](18-) and [[([alpha]-[Ti.sub.3]Si[W.sub.9][O.sub.37]OH).sub.3](Ti[O.sub.3][([OH.sub.2]).sub.3])](17-) as the first examples of trimeric Ti-containing polytungstates are reported. Both the complexes are composed of three ([Ti.sub.3]X[W.sub.9][O.sub.37]) units (X = P or Si) linked via three Ti-O-Ti bridges and a capping group, which is either tetrahedral P[O.sub.4] or octahedral Ti[O.sub.6].

The transition of the ionic properties of the oxothiomolybdate ring from an anionic to cationic receptor is explained. The transition is shown to be result of the ionization of the internal aquo ligands.

Research has been conducted on [(PW (sub)11 O (sub)39) (sub)2 (H (sub)4 Mo (sub)4 S (sub)4 O (sub)6)] (super)10- anions. The authors demonstrate that these anions have been produced via stereospecific addition of the oxothiocation to the monovacant anion.

This paper deals with the electrochemical studies performed in DMF on three iso-electronic compounds of general formula γ-[SiW10O36(M2O2E2)]6−, which differ either with respect to the nature of their metallic centers (M = Mo(v) or W(v)) or the nature of the bridges between the Mo(v) atoms (E = O2− or S2−). Interestingly, cyclic voltammetry experiments performed in dry DMF revealed electrochemical processes both in oxidation and reduction modes. The nature of these processes is studied and elucidated by various electrochemical techniques such as coulometry, rotating disk voltammetry, spectro-electrochemistry (IR and UV-Vis), and NMR and DFT calculations. [ABSTRACT FROM AUTHOR]