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Supramolecular polymers built from stimuli‐responsive host‐guest interactions represent an attractive way of tailoring smart materials. Herein, we exploit the chaotropic effect of polyoxometalates and related host‐guest properties to design unconventional polymer systems with reversible redox and thermo‐responsive sol‐gel transition. These supramolecular networks result from the association of cyclodextrin‐based oligomers and Keggin‐type POMs acting as electro‐active crosslinking agents. The structure and the dynamics of such self‐assembly systems have been investigated using a multiscale approach involving MALDI‐TOF, viscosity measurements, cyclic voltammetry, 1H‐NMR (1D and DOSY), and Small‐Angle X‐ray Scattering. Our results reveal that the chaotropic effect corresponds to a powerful and efficient force that can be used to induce responsiveness in hybrid supramolecular oligomeric systems. [ABSTRACT FROM AUTHOR]

Super‐reduction of polyoxometalates (POMs) in solution is of fundamental interest for designing innovative energy storage systems. In this article, we show that the "Dawson‐like" POM can undergo a disproportionation process during its massive electron uptake, leading to species containing three metal‐metal bonds as evidenced by X‐ray diffraction, multi‐nuclear magnetic resonance spectroscopy (1H and 183W NMR), extended X‐ray absorption fine structure (EXAFS), UV/Vis, and voltammetry techniques. This result indicates that electron storing within metal‐metal bonds is not a unique property of Keggin‐type POM as postulated since the 70s. Besides, we demonstrate that the presence of an electron‐rich triad in the "Dawson‐like" POM allows its post‐functionalization with additional tungstate ions, generating a chiral molecule that is also the largest WIV‐containing POMs known to date. [ABSTRACT FROM AUTHOR]

Super‐reduction of polyoxometalates (POMs) in solution is of fundamental interest for designing innovative energy storage systems. In this article, we show that the "Dawson‐like" POM can undergo a disproportionation process during its massive electron uptake, leading to species containing three metal‐metal bonds as evidenced by X‐ray diffraction, multi‐nuclear magnetic resonance spectroscopy (1H and 183W NMR), extended X‐ray absorption fine structure (EXAFS), UV/Vis, and voltammetry techniques. This result indicates that electron storing within metal‐metal bonds is not a unique property of Keggin‐type POM as postulated since the 70s. Besides, we demonstrate that the presence of an electron‐rich triad in the "Dawson‐like" POM allows its post‐functionalization with additional tungstate ions, generating a chiral molecule that is also the largest WIV‐containing POMs known to date. [ABSTRACT FROM AUTHOR]

Natural cyclodextrin (CD) macrocycles are known to form diverse inclusion complexes with a wide variety of organic molecules, but recent work has revealed that inorganic clusters also form multicomponent supramolecular complexes and edifices. Such molecular assemblies exhibit a high degree of organization in solution governed by various chemical processes including molecular recognition, host-guest attraction, hydrophobic repulsion, or chaotropic effect. Nuclear magnetic resonance (NMR) spectroscopy is one of the most efficient and practical analytical techniques to characterize the nature, the strength and the mechanism of these interactions in solution. This review provides a brief overview on recent examples of the contribution of NMR to the characterization of hybrid systems in solution based on CD with polynuclear clusters, including polyoxometalates (POMs), metallic clusters and hydroborate clusters. The focus will be first on using ¹H (and 13C) NMR of the host, i.e., CD, to identify the nature of the interactions and measure their strength. Then, 2D NMR methods will be illustrated by DOSY as a means of highlighting the clustering phenomena, and by NOESY/ROESY to evidence the spatial proximity and contact within the supramolecular assemblies. Finally, other NMR nuclei will be selected to probe the inorganic part as a guest molecule. Attention will be paid to classical host-guest complexes Cluster@CD, but also to hierarchical multi-scale, multi-component assemblies such as Cluster@CD@Cluster. [ABSTRACT FROM AUTHOR]

Evidence for photoinduced intermolecular electron transfer from the excited state of the [Mo6I8Cl6]2− electron-rich cluster to polyoxometalates (POMs) is reported. We demonstrate that the global charge density of POMs affects the efficiency of electron transfer. This work paves the way for the rational design of photocatalytic systems using cluster-based complexes as robust noble-metal-free photosensitizers. [ABSTRACT FROM AUTHOR]

Host–guest assemblies open up opportunities for developing novel functional CLUSPOM multicomponent systems based on transition metal clusters (CLUS), polyoxometalates (POMs) and macrocyclic organic ligands. In water–ethanol solution γ-cyclodextrin (γ-CD) interacts with halide metal clusters [M6Cl14]2– (M = Mo, W) to form sandwich-type structures. The supramolecular association between the clusters and CDs, however, remains weak in solution, and the interactions are not strong enough to prevent the hydrolysis of the inorganic guest. Although analysis of the resulting crystal structures reveals inclusion complexation, 1H NMR experiments in solution show no specific affinity between the two components. The luminescent properties of the host–guest compounds in comparison with the initial cluster complexes are also studied to evaluate the influence of CD. [ABSTRACT FROM AUTHOR]

Noncovalent ionic interactions between nanosized Keplerate-type capsules {Mo132} and tetra-cationic porphyrins have been investigated in aqueous solution using small-angle X-ray scattering, 1H NMR and photophysical methods. These complementary multiscale methods reveal the formation of large hybrid oligomers built from a short-range organization in which the cationic porphyrin is glued onto the large POM surface. The local structuring appears to be strongly dependent on the dye : {Mo132} ratio changing the morphology of the oligomers from linear to dense aggregates. [ABSTRACT FROM AUTHOR]

Herein we report the synthesis of a new class of compounds associating Keggin and Dawson-type Polyoxometalates (POMs) with a derivative of the anionic decahydro-closo-decaborate cluster [B10H10]2− through aminopropylsilyl ligand (APTES) acting as both a linker and a spacer between the two negatively charged species. Three new adducts were isolated and fully characterized by various NMR techniques and MALDI-TOF mass spectrometry, notably revealing the isolation of an unprecedented monofunctionalized SiW10 derivative stabilized through intramolecular H-H dihydrogen contacts. DFT as well as electrochemical studies allowed studying the electronic effect of grafting the decaborate cluster on the POM moiety and its consequences on the hydrogen evolution reaction (HER) properties. [ABSTRACT FROM AUTHOR]

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]

Host‐guest complexes between native cyclodextrins (α‐, β‐ and γ‐CD) and hybrid Lindqvist‐type polyoxovanadates (POVs) [V6O13((OCH2)3C−R)2]2– with R = CH2CH3, NO2, CH2OH and NH(BOC) (BOC = N‐tert‐butoxycarbonyl) were studied in aqueous solution. Six crystal structures determined by single‐crystal X‐ray diffraction analysis revealed the nature of the functional R group strongly influences the host–guest conformation and also the crystal packing. In all systems isolated in the solid‐state, the organic groups R are embedded within the cyclodextrin cavities, involving only a few weak supramolecular contacts. The interaction between hybrid POVs and the macrocyclic organic hosts have been deeply studied in solution using ITC, cyclic voltammetry and NMR methods (1D 1H NMR, and 2D DOSY, and ROESY). This set of complementary techniques provides clear insights about the strength of interactions and the binding host‐guest modes occurring in aqueous solution, highlighting a dramatic influence of the functional group R on the supramolecular properties of the hexavanadate polyoxoanions (association constant K1:1 vary from 0 to 2 000 M−1) while isolated functional organic groups exhibit only very weak intrinsic affinity with CDs. Electrochemical and calorimetric investigations suggest that the driving force of the host‐guest association involving larger CDs (β‐ and γ‐CD) is mainly related to the chaotropic effect. In contrast, the hydrophobic effect supported by weak attractive forces appears as the main contributor for the formation of α‐CD‐containing host‐guest complexes. In any cases, the origin of driving forces is clearly related to the ability of the macrocyclic host to desolvate the exposed moieties of the hybrid POVs. [ABSTRACT FROM AUTHOR]

Herein, we show how the chaotropic effect arising from reduced molybdate ions in acidified aqueous solution is able to amplify drastically weak supramolecular interactions. Time‐resolved Small Angle X‐ray Scattering (SAXS) analysis suggests that molybdenum‐blue oligomeric species form huge aggregates in the presence of γ‐cyclodextrin (γ‐CD) which results in the fast formation of nanoscopic {Mo154}‐based host‐guest species, while X‐ray diffraction analysis reveals that the ending‐point of the scenario results in an unprecedented three‐component well‐ordered core–shell‐like motif. A similar arrangement was found by using preformed hexarhenium chalcogenide‐type cluster [Re6Te8(CN)6]4− as exogenous guest. This seminal work brings better understanding of the self‐assembly processes in general and gives new opportunities for practical applications in the design of complex multicomponent materials via the simplicity of the non‐covalent chemistry. [ABSTRACT FROM AUTHOR]

Herein, we show how the chaotropic effect arising from reduced molybdate ions in acidified aqueous solution is able to amplify drastically weak supramolecular interactions. Time‐resolved Small Angle X‐ray Scattering (SAXS) analysis suggests that molybdenum‐blue oligomeric species form huge aggregates in the presence of γ‐cyclodextrin (γ‐CD) which results in the fast formation of nanoscopic {Mo154}‐based host‐guest species, while X‐ray diffraction analysis reveals that the ending‐point of the scenario results in an unprecedented three‐component well‐ordered core–shell‐like motif. A similar arrangement was found by using preformed hexarhenium chalcogenide‐type cluster [Re6Te8(CN)6]4− as exogenous guest. This seminal work brings better understanding of the self‐assembly processes in general and gives new opportunities for practical applications in the design of complex multicomponent materials via the simplicity of the non‐covalent chemistry. [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]

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]

A novel decahydrodecaborate-functionalized Anderson type polyoxometalate has been synthesized and characterized in solution by ESI-MS, various NMR techniques and electrochemical methods. DFT studies provide strong support to understand the properties of this hybrid system. [ABSTRACT FROM AUTHOR]

We report how only one electron transfer from the hydrophilic reduced cluster [{Re6Se8}(CN)6]4− induces both a dramatic increase of the host–guest affinity with γ-cyclodextrin and a drastic alteration of the supramolecular dynamics. This striking behaviour, underlined by its thermochemical fingerprint, indicates that the self-assembly process is driven by a chaotropic effect. [ABSTRACT FROM AUTHOR]

This paper deals with the formation of host‐guest systems between cyclodextrins and the closo‐decahydrodecaborate cluster. The inclusion processes, although involving weak interaction, were evidenced in solution by ESI‐MS and various NMR techniques. ITC measurements provided thermodynamic parameters, and DFT calculations gave some elements that help in understanding these processes. [ABSTRACT FROM AUTHOR]

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]

Abstract: Water‐soluble salts of anionic [Re6Q8(CN)6]4− (Q=S, Se, Te) chalcogenide octahedral rhenium clusters react with γ‐cyclodextrin (γ‐CD) producing a new type of inclusion compounds. Crystal structures determined through single‐crystal X‐ray diffraction analysis revealed supramolecular host–guest assemblies resulting from close encapsulations of the octahedral cluster within two γ‐CDs. Interestingly, nature of the inner Q ligands influences strongly the host–guest conformation. The cluster [Re6S8(CN)6]4− interacts preferentially with the primary faces of the γ‐CD while the bulkier clusters [Re6Se8(CN)6]4− and [Re6Te8(CN)6]4− exhibit specific interactions with the secondary faces of the cyclic host. Furthermore, analysis of the crystal packing reveals additional supramolecular interactions that lead to 2D infinite arrangements with [Re6S8(CN)6]4− or to 1D “bamboo‐like” columns with [Re6Se8(CN)6]4− and [Re6Te8(CN)6]4− species. Solution studies, using multinuclear NMR methods, ESI‐MS and Isothermal titration calorimetry (ITC) corroborates nicely the solid‐state investigations showing that supramolecular pre‐organization is retained in aqueous solution even in diluted conditions. Furthermore, ITC analysis showed that host–guest stability increases significantly ongoing from S to Te. At last, we report herein that deep inclusion alters significantly the intrinsic physical‐chemical properties of the octahedral clusters, allowing redox tuning and near IR luminescence enhancement. [ABSTRACT FROM AUTHOR]

Slow evaporation of water solution of [{ReS}(HO)] generated in situ from [{ReS}(OH)] in presence of γ-cyclodextrin (CD) leads to crystallization of {[{ReS}(HO)] ⊂ [γ-CD]}(NO)·12HO ( 1·12HO) supramolecular complex, which was characterized by single-crystal X-ray diffraction crystallography, IR-spectroscopy, thermogravimetric and elemental analyses. X-ray analysis confirms the formation of 1:1 {[{ReS}(HO)] ⊂ [γ-CD]} inclusion compound in the solid state. However, no adduct formation was detected between [{ReS}(HO)] and γ-cyclodextrin in solution, according to H NMR spectroscopy. In the case of in situ generated [{ReSe}(HO)] the reaction solution with γ-cyclodextrin is unstable and during the crystallization only amorphous precipitate has been obtained. [ABSTRACT FROM AUTHOR]

The potential of high-field NMR to measure solid-state 95Mo and 183W NMR in polyoxometalates (POMs) is explored using some archetypical structures like Lindqvist, Keggin and Dawson as model compounds that are well characterized in solution. NMR spectra in static and under magic angle spinning (MAS) were obtained, and their analysis allowed extraction of the NMR parameters, including chemical shift anisotropy and quadrupolar coupling parameters. Despite the inherent difficulties of measurement in solid state of these low-gamma NMR nuclei, due mainly to the low spectral resolution and poor signal-to-noise ratio, the observed global trends compare well with the solution-state NMR data. This would open an avenue for application of solid-state NMR to POMs, especially when liquid-state NMR is not possible, e.g., for poorly soluble or unstable compounds in solution, and for giant molecules with slow tumbling motion. This is the case of Keplerate where we provide here the first NMR characterization of this class of POMs in the solid state. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A semi-empirical approach based on the partial charge formalism has been used to calculate 183W NMR chemical shifts in polyoxotungstates (POTs). Good consistency between calculations and experimental measurements allowed determining the main effective parameters for modeling the electronic state of the {WVIO6} centers. As the three 183W NMR chemical shifts of the {P8W48O184} macrocycle exhibit strong pH dependence, partial charge model calculations have been carried out for the investigation of the protonation of the metal–oxo framework. Furthermore, these calculations highlight the effect of the potassium ions embedded within the internal cavity. In this work, NMR parameters were computed using the PACHA software, distinguishing and assigning 183W NMR resonances. [ABSTRACT FROM AUTHOR]

Five new tartrate-containing Keplerate compounds have been synthesized and characterized in the solid state and in solution. These characterizations evidenced the total replacement of inner sulfate ligands by L- or D-tartrate ligands in aqueous medium under heating during several days. To our knowledge these compounds correspond to the first Keplerate molecules incorporating chiral ligands. The H NMR studies supported by X-ray crystallographic analysis are consistent with the coordination of 24-30 tartrates within the Mo capsule which are located in close vicinity. The NMR signals of the encapsulated ligands appear particularly broad which precludes the use of advanced NMR methodologies but the solid state NMR provided further characterization of ligand substitution within the capsule by carboxylates. To our knowledge it is the first time that a solid state NMR study of a Keplerate is reported in the literature. [ABSTRACT FROM AUTHOR]

This paper summarizes preparations of mixed phosphoniobotungstates [PNbxW12−xO40](3+x)− (x = 1–3) in two different ways: (i) incorporation of Nb into pre-existing lacunary phosphotungstates and (ii) self-assembly reactions. A niobium oxalate complex as the source of niobium is used. The reaction products were monitored by 31P and 183W NMR in solution as well as by 31P MAS NMR techniques for precipitated samples. Single-substituted species [PNbW11O40]4− forms rapidly and selectively from lacunary [PW11O39]7− with one equivalent of [NbO(C2O4)2(H2O)2]−. With the increasing amount of the niobium oxalate the highest number of Nb atoms was found to be three per Keggin anion, but the disubstituted [PNb2W10O40]5− was always the preferable product whatever the tungsten reagent was. The reaction products with x = 2 and 3 are present as mixtures of all possible isomers, but the ratio between the individual isomers depends on the synthetic pathway. [ABSTRACT FROM AUTHOR]

The internal functionalization of the Keplerate-type capsule Mo132 has been carried out by ligand exchange leading to the formation of glutarate and succinate containing species isolated as ammonium or dimethylammonium salts. Solution NMR analysis is consistent with asymmetric inner dicarboxylate ions containing one carboxylato group grafted onto the inner side of the spheroidal inorganic shell while the second hangs toward the center of the cavity. Such a disposition has been confirmed by the single-crystal X-ray diffraction analysis of the glutarate containing {Mo132} species. A detailed NMR solution study of the ligand-exchange process allowed determining the binding constant KL of acetate (AcO−), succinate (HSucc−) or glutarate (HGlu−) ligands at the 30 inner coordinating sites, which vary such as K [ABSTRACT FROM AUTHOR]

Two dimethyldioctadecylammonium (DODA+) salts of a new keplerate with the general formula [Mo132O312S60(SO4)x(H2O)132–2x](12 + 2x)−and abbreviatedDODAn−Mo132S60(n= 44, 56) were synthesised and characterised. Both clusters were fully characterised by the combination of Polarised Optical Microscopy, Differential Scanning Calorimetry and Small-angle X-Ray Diffraction showing self-organisation in lamellar (L) liquid crystalline phases. We demonstrated that the lamellar periodicityhof the mesophases can be controlled with the number of DODA+associated to the clusters. Finally, these new results were compared to those gained from a previously published analogue, the fully oxo keplerate noted DODA36−Mo132that also self-organise with temperature, but in a slightly more structured lamellar liquid crystalline phase. [ABSTRACT FROM AUTHOR]

Bionanocomposite films on glassy carbon electrodes (GCEs) have been prepared by a very straightforward and reliable method based on a layer-by-layer deposition of polyoxometalate (POM) (i.e. [BW12O40]5-) and gelatin solutions. The strong immobilisation of [BW12O40]5- on the surface of the GCE results from electrostatic interactions between gelatin and POM, as evidenced in a hybrid hydrogel prepared by a coacervation process. The GCE has also been modified by imidazolium based ionic liquids in order to increase the charge transfer rate. Two modified electrodes with one or two POM layers have been prepared by this strategy. When compared to other POM-based modified electrodes, the novel electrodes with two POM layers exhibit excellent electrocatalytic performance for nitrite detection at pH 3 in terms of sensitivity (868 mA M-1 cm-2) and linear range of nitrite concentrations (50-600 μM). [ABSTRACT FROM AUTHOR]

The complexes [MoOS(OH)(abtc)(HO)] ( 1) and [MoOS(OH)(abtc)(HO)] ( 2) (abtc = 3,5-dicarboxyl-(3′,5′-dicarboxyazophenyl)benzene) have been obtained from the condensation of the [MoOS] cluster in the presence of abtc ligand. Compounds 1 and 2 were characterized structurally, revealing host-guest architectures containing one or two encapsulated abtc ligands. In 1, the guest abtc moieties appears firmly coordinated to the ring by the four carboxylato groups, giving a nearly planar conformation which fall in the plane of the sixteen Mo atoms of the inorganic macrocycle. Conversely, the two equivalent abtc ligands in 2 exhibit an asymmetric mode of coordination, where two carboxylato groups are coordinated to the {Mo} ring and the two remaining hang outer the open cavity. Anions 1 and 2 have been characterized by H NMR in solution, revealing for 1 an enhancement of the symmetry likely due to some molecular dynamic, while the compound 2 easily converts into 1 with a consecutive release of one abtc ion. Furthermore, a solution study showed that the formal linkage of the two isophatlate moieties through an azo {N=N} unit brings a drastic stability increase of the host-guest assembly compared to the bis-isophtalate containing {Mo} ring. Synthesis, elemental analysis, and infrared spectra are also supplied. [ABSTRACT FROM AUTHOR]

Two nanosized polyoxothiometalates were synthesized based on linking oxomolybdate building blocks with {Mo2O2S2}2+ groups. Remarkably, both compounds are formed selectively primarily upon changing the related concentrations in a logical way; they exhibit common structural features based on the same {Mo9O6S3}-type pores, which result in connections between {Mo6O21} pentagons and {Mo2O2S2}2+ linkers. Whereas the much larger spherical Mo132-type Keplerate contains twenty pores, the smaller Mo63-type cluster remarkably contains only two. The two compounds and a similar Keplerate exhibit interesting supramolecular properties related to interactions with the unusual predominantly apolar NMe4+ cations. Structural characterization of the Mo63-type compound reveals in the solid state a clathrate-like species that contains four NMe4+ cations embedded in two types of structurally well-adapted pockets. Related NMR spectroscopic investigations in solution using NMe4+ as the NMR spectroscopic probe are in agreement with the solid-state description. 1H NMR spectroscopic experiments (1D variable-temperature, 2D total correlation spectroscopy (TOCSY), exchange spectroscopy (EXSY), and diffusion-ordered spectroscopy (DOSY)) feature firmly immobilized and mobile NMe4+ ions in relationship with the type of host-guest arrangements. The use of the 1H NMR DOSY spectroscopic methodology has been successfully applied to track the interactions of the NMe4+ cations with the {Mo9O6S3} pores of a sulfurated Keplerate, thereby allowing the first quantitative analysis of this type of plugging process. The stability constant K=(210±20) mol−1 L is discussed related to the character of the process. [ABSTRACT FROM AUTHOR]

The connection of flexible protodendritic wedges to the bis-tridentate rigid polyaromatic ligand L1 provides amphiphilic receptors L5 and L6; their reduced affinities for complexing trivalent lanthanides (Ln = La, Y, Lu) in organic solvent (by fifteen orders of magnitude!) prevent the formation of the expected dinuclear triple-stranded helicates [Ln2( L k)3]6+. This limitation could be turned into an advantage because L1 or L6 can be treated with [Ln(hfac)3] (Hhfac = 1,1,1,5,5,5-hexafluoro-2,4-pentanedione) to give neutral single-stranded [Ln2( L k)(hfac)6] complexes with no trace of higher-order helicates. Whereas ligands L1 and L5 are not liquid crystals, L6 can be melted above room temperature (41 °C) to give a nematic mesophase, and its associated dinuclear helical complex [Y2( L6)(hfac)6] self-organises at the same temperature into a fluidic smectic mesophase. [ABSTRACT FROM AUTHOR]

The reaction of {SbW9O33}9- with {Mo2O2S2}2+ has been studied. The {SbW9O33}{Mo2O2S2} products are labile in solution and very sensitive to experimental conditions. Two new hybrids, {Mo2O2S2}-containing tungstoantimonate anions, namely [(SbW9O33)2(Mo2O2S2)3]12- and [K(SbW9O33)2(Mo2O2S2)WO(H2O)]11-, have been fully characterized in the solid state and in solution by 183W NMR spectroscopy. [ABSTRACT FROM AUTHOR]

The polymetallic cation [Mo3S4(H2O)9]4+ was used as an inorganic precursor to generate new hybrid organic-inorganic chalcogenide clusters. Three organic compounds with flexible and hanging arms were synthesized and investigated as ligands for coordination complexes with the rigid and electroactive inorganic {Mo3S4} unit. Interestingly, the {Mo3S4} core formed hybrid structures with the flexible H3NDABu [ N-(3-carboxypropyl)iminodiacetic acid] and H3NDAPr [ N-(2-carboxyethyl)iminodiacetic acid] ligands, which were characterized by X-ray crystallography. Surprisingly, no crystals were isolated, when the more rigid H3NDABn [ N-(4-methoxycarbonylbenzyl)iminodiacetic acid] ligand was used. The two coordination complexes [Mo3S4(NDABu)(HNDABu)2]3- and [Mo3S4(HNDAPr)3]2- were characterized by X-ray diffraction (XRD), IR spectroscopy, thermal gravimetric analysis (TGA), 1H NMR spectroscopy, elemental analysis, and electrochemistry. The organic ligands H3NDABu, H3NDAPr, and H3NDABn were characterized by XRD, IR, HR mass, and 13C and 1H NMR spectroscopy. [Mo3S4(NDABu)(HNDABu)2]3- and [Mo3S4(HNDAPr)3]2- constitute promising preformed building blocks to generate new organic-inorganic hybrid molecular or extended materials. [ABSTRACT FROM AUTHOR]

Thermal studies of a DODA+ salt of the nanoscopic hollow sphere [Mo132O372(H2O)72(CH3CO2)30]42− revealed ionic liquid crystalline properties, which were evidenced by Polarised Optical Microscopy, DSC and SA-XRD. [ABSTRACT FROM AUTHOR]

The last decade has see the development of sulfur-containing polyoxometalates (POTMs) as a subclass of the polyoxometalate family. The structural and physico-chemical properties of this emerging class of compounds is dominating by the striking coordination properties of the [MoOS(OH)] oxothio cation, used as a building block. The cyclic topology of this arrangement corresponds to the main feature of the {MoOS}-based compounds, able to develop cycle-based chemistry. The control of the linear oligomerization of the {MoOS} core is achieved by the presence of the anionic component, which acts as a template. Here, we report on recent examples which illustrate how the use of various template ions such as halide, sulfate, polyphosphate, and polycarboxylate anions allows to tune the nuclearity of the inorganic host from {Mo} to {Mo}. A special focus on behavior in solution is given, highlighting the dynamic and fluxional character of these host-guest systems. The Diffusion Ordered Spectroscopy (DOSY) H NMR, carried out on a large series of cycle-based and capsule-like compounds, demonstrates that such a method can be applied for the speciation of POM anions in solution. Finally, electrocatalytic behavior of the {MoOS}-based compounds is presented. Preliminary results show that the electrocatalytic reduction of protons into hydrogen (HER) could constitute one of the most relevant applications for this class of molecular compounds. [ABSTRACT FROM AUTHOR]

The novel polyoxothioanion [Mo4S4O4(OH)2(OH2)3pba]2− where pba4− ligand is the 1,3-propylenebis(oxamate), was prepared by reacting Mo12S12O12(OH)12(OH2)6 ring with [Cu-pba]2− in aqueous medium. NaK[Mo4O4(μ-S)4(μ-OH)2(μ-H2O)(H2O)2(pba)] ·7H2O was isolated in the solid state and fully characterized by X-ray diffraction study (tetragonal, P4(2)/m [ a=20.4962(4) Å; b=20.4962(4) Å; c=14.7013(5) Å). The molecular structure consists of an arc cycle shape tetranuclear enchainment {Mo4S4O4(OH)2 (OH2)3} closed by a pba4− ligand. The 3-D packing, resulting from the connection between K+ and Na+ and the coordination complex {Mo4-pba]2− is described. The 1H-NMR characterization of the complex in aqueous solution is given. The 1H-NMR spectrum exhibits four signals assigned to four enantiotopic protons of the alkyl chain of the pba4− ligand and is in agreement with crystal structure of the complex [Mo4-pba]2−. The compound was also characterized by infrared spectroscopy. [ABSTRACT FROM AUTHOR]

Discusses the synthesis, structure and properties of the cyclic mixed valence oxothiotungstate. Preparation of the novel polyoxothioanion by acido-basic condensation of four thiofragments in the presence of tungstate ion; Presence of an octametric wheel in the molecular structure; Encapsulation of a central octahedron.