Publications by authors named "Emmanuel Cadot"

54 Publications

Redox-Responsive Host-Guest Association between γ-Cyclodextrin and Mixed-Metal Keggin-Type Polyoxometalates.

Inorg Chem 2021 Apr 29. Epub 2021 Apr 29.

Institut Lavoisier de Versailles, UMR 8180 CNRS, UVSQ, Université Paris-Saclay, Versailles 78035, France.

The complexation of Keggin-type polyoxometalates (POMs) with γ-cyclodextrin (γ-CD) leads to supramolecular inclusion assemblies in aqueous solution driven by a chaotropic effect. The strength of the interaction between γ-CD and oxidized or one-electron reduced POMs in a series of molybdenum and vanadium monosubstituted phospho- and silico-tungstates, [XWMO] Keggin-type anions where X = P or Si and M = Mo or V, has been evaluated by isothermal titration calorimetry (ITC), NMR spectroscopy, and cyclic voltammetry. Such a study reveals that the host-guest binding constant increases strongly with the decrease of the global ionic charge of the POM unit. There is an almost one magnitude order of variation in per charge unit, where falls down from about 10 M to values close to zero as ionic charge varies from 3- to 6-. Such POMs with molybdenum and vanadium addenda offer the possibility of tuning the host-guest association strength by the simple addition/removal of one electron to POMs, opening a new avenue for the design of smart materials through redox stimuli.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.inorgchem.1c00724DOI Listing
April 2021

"Host in Host" Supramolecular Core-Shell Type Systems Based on Giant Ring-Shaped Polyoxometalates.

Angew Chem Int Ed Engl 2021 Mar 16. Epub 2021 Mar 16.

Institut Lavoisier de Versailles, CNRS, UVSQ, Université Paris-Saclay, Versailles, France.

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 {Mo }-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 [Re Te (CN) ] 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.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/anie.202102507DOI Listing
March 2021

Discovery and Supramolecular Interactions of Neutral Palladium-Oxo Clusters Pd and Pd.

Angew Chem Int Ed Engl 2021 Feb 15;60(7):3632-3639. Epub 2020 Dec 15.

Department of Life Sciences and Chemistry, Jacobs University, Campus Ring 1, 28759, Bremen, Germany.

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 [Pd O (OH) ((CH ) As) ] (Pd ) comprises a cyclic palladium-oxo unit capped by eight dimethylarsinate groups. The chloro-derivative [Pd Na O (OH)  Cl  ((CH )  As) ] (Pd Cl) was also prepared, which forms a highly stable 3D supramolecular lattice via strong intermolecular interactions. The 24-palladium(II)-oxo cluster [Pd O (OH) ((CH ) As) ] (Pd ) can be considered as a bicapped derivative of Pd 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 H and C NMR spectroscopy, 2) in solution by H, C NMR and H DOSY spectroscopic methods, and 3) in the gas phase by electrospray ionization mass spectrometry (ESI-MS).
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/anie.202010690DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7898824PMC
February 2021

Cyclodextrin-Assisted Hierarchical Aggregation of Dawson-type Polyoxometalate in the Presence of {ReSe} Based Clusters.

Inorg Chem 2020 Aug 24;59(16):11396-11406. Epub 2020 Jul 24.

Institut Lavoisier de Versailles, UMR 8180 CNRS, UVSQ, Université Paris-Saclay, Versailles, France.

The association of metallic clusters (CLUS) and polyoxometalates (POM) into hierarchical architectures is achieved using γ-cyclodextrin (γ-CD) as a supramolecular connector. The new self-assembled systems, so-called CLUSPOM, are formed from Dawson-type polyoxometalate [PWO] and electron-rich rhenium clusters. It is worth noting that a cluster-based cation [{ReSe}(HO)] on one hand and a cluster-based anion on the other hand [{ReSe}(CN)] can be associated with the anionic POM. In the absence of the supramolecular connector, a "CLUSPOM salt" was obtained from aqueous solution of the cationic cluster and the polyoxometalate. In this solid, the arrangement between the polymetallic building blocks is mainly governed by long-range Coulombic interactions. In the presence of γ-CD, the Dawson anion and the cationic cluster are assembled differently, forming a hierarchical supramolecular solid, K[{ReSe}(HO)]{[PWO]@2γ-CD}·42HO, where the organic macrocycle acts as a ditopic linker between the inorganic building blocks. In such an edifice, the short-range molecular recognition dominates the long-range Coulombic interactions leading to a specific three-dimensional organization. Interestingly, the assembling of anionic POM [PWO] with the anionic rhenium cluster [{ReSe}(CN)] is also achieved with γ-CD despite the repulsive forces between the nanosized anions. The resulting solid, K{[{ReSe}(CN)]@2γ-CD}[PWO]·33HO, is built from 1:2 inclusion complexes {[{ReSe}(CN)]@2γ-CD} linked by a POM unit interacting with the exterior wall of the organic macrocycle. Multinuclear NMR and small-angle X-ray scattering investigations support supramolecular preorganization in aqueous solution prior to crystallization.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.inorgchem.0c01160DOI Listing
August 2020

Unprecedented coupling reaction between two anionic species of a closo-decahydrodecaborate cluster and an Anderson-type polyoxometalate.

Dalton Trans 2020 Apr 25;49(15):4685-4689. Epub 2020 Mar 25.

Institut Lavoisier de Versailles, CNRS, UVSQ, Université Paris-Saclay, 45 av. des Etats-Unis, 78035, Versailles, France.

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.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c9dt04676cDOI Listing
April 2020

From Specific γ-CD/[Nb Cl (H O) ] Recognition to Biological Activity Tuning.

Chemistry 2020 Jun 19;26(33):7479-7485. Epub 2020 May 19.

Nikolaev Institute of Inorganic Chemistry SB RAS, 3 acad. Lavrentiev ave., 630090, Novosibirsk, Russia.

Specific molecular recognition of γ-cyclodextrin (γ-CD) by the cationic hexanuclear niobium [Nb Cl (H O) ] cluster complex in aqueous solutions results in a 1:1 supramolecular assembly {[Nb Cl (H O) ]@γ-CD} . 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 [Nb Cl (H O) ] , 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 [Nb Cl (H O) @(γ-CD) ]Cl ⋅20 H O 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.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/chem.202000739DOI Listing
June 2020

Size-Exclusion Mechanism Driving Host-Guest Interactions between Octahedral Rhenium Clusters and Cyclodextrins.

Inorg Chem 2019 Oct 25;58(19):13184-13194. Epub 2019 Sep 25.

Institut Lavoisier de Versailles , UMR 8180 CNRS, UVSQ, Université Paris-Saclay , Versailles , France.

In aqueous solution, cyclodextrins (CDs) are able to bind strongly either hydrophobic species or also hydrophilic molecules such as octahedral hexametallic cluster. Systematic investigation of the reactivity between native CDs (α- or β-CD) and water-soluble rhenium clusters [ReQ(CN)] with Q = S, Se, and Te were performed, leading to six new crystal structures revealing different types of supramolecular arrangements. Encapsulation of [ReQ(CN)] (Q = S, Se, or Te) within two β-CDs is observed regardless of the cluster size. Interestingly, different assembling scenarios are pointed out depending on the host-guest matching featured by no, partial, or deep inclusion complexes that involved either primary or secondary rim of the CD tori. In the specific case of α-CD, only the smaller cluster [ReS(CN)] is able to form inclusion complex with the tori host. Solution investigations, using a set of complementary techniques including isothermal titration calorimetry, multinuclear NMR methods, cyclic voltammetry, and electrospray ionization mass spectrometry, corroborate nicely conclusions of the solid-state studies. It appears clearly that size-matching supported by solvent effects play key roles in the stability of the host-guest complexes. At last, circular dichroism studies underline that the chirality induction from cyclodextrins to the rhenium cluster depends strongly on the strength of host-guest interactions.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.inorgchem.9b02048DOI Listing
October 2019

Polyoxothiometalate-Derivatized Silicon Photocathodes for Sunlight-Driven Hydrogen Evolution Reaction.

ACS Omega 2018 Oct 22;3(10):13837-13849. Epub 2018 Oct 22.

Institut Lavoisier de Versailles (UMR-CNRS 8180), UVSQ, Université Paris-Saclay, 45 Avenue de Etats-Unis, 78000 Versailles, France.

Silicon photocathodes coated with drop-casted {MoS}-based polyoxothiometalate assemblies are demonstrated to be effective for sunlight-driven hydrogen evolution reaction (HER) in acid conditions. These photocathodes are catalytically more efficient than that coated with the parent thiomolybdate incorporating an organic ligand, as supported by a higher onset potential and a lower overvoltage at 10 mA cm. At pH 7.3, the trend is inversed and the beneficial effect of the polyoxometalate for the HER is not observed. Moreover, the polyoxothiometalate-modified photocathode is found to be also more stable under acid conditions and can be operated at the light-limited catalytic current for more than 40 h. Furthermore, X-ray photoelectron spectroscopy and atomic force microscopy measurements indicate that the cathodic polarization of both photocathodes leads to the release of a large amount of the deposited material into the electrolyte solution concomitantly with the formation of mixed valence species {Mo(IV) Mo(III) O S } resulting from the replacement of S sulfido ligands in the cluster by oxo O groups; these combined effects are shown to be beneficial for the photoelectrocatalysis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acsomega.8b01734DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6645094PMC
October 2018

Tuning the chaotropic effect as an assembly motif through one-electron transfer in a rhenium cluster.

Chem Commun (Camb) 2019 Aug 30;55(67):9951-9954. Epub 2019 Jul 30.

Institut Lavoisier de Versailles, CNRS, UVSQ, Université Paris-Saclay, Versailles, France.

We report how only one electron transfer from the hydrophilic reduced cluster [{ReSe}(CN)] 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.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c9cc05136hDOI Listing
August 2019

Molecular and Material Engineering of Photocathodes Derivatized with Polyoxometalate-Supported {MoS} HER Catalysts.

J Am Chem Soc 2019 Jul 10;141(30):11954-11962. Epub 2019 Jul 10.

Université Reims Champagne Ardenne , Institut de Chimie Moléculaire de Reims (ICMR), UMR7312 CNRS-URCA, Moulin de la Housse, BP 1039, 51687 Reims Cedex 2 , France.

Molecular engineering of efficient HER catalysts is an attractive approach for controlling the spatial environment of specific building units selected for their intrinsic functionality required within the multistep HER process. As the {MoS} core derived as various coordination complexes has been identified as one as the most promising MoS-based HER electrocatalysts, we demonstrate that the covalent association between the {MoS} core and the redox-active macrocyclic {PW} polyoxometalate (POM) produces a striking synergistic effect featured by high HER performance. Various experiments carried out in homogeneous conditions showed that this synergistic effect arises from the direct connection between the {MoS} cluster and the toroidal {PW} units featured by a stoichiometry that can be tuned from two to four {MoS} cores per {PW} unit. In addition, we report that this effect is preserved within heterogeneous photoelectrochemical devices where the {MoS}-{PW} (thio-POM) assembly was used as cocatalyst () onto a microstructured p-type silicon. Using a drop-casting procedure to immobilize onto the silicon interface led to high initial HER performance under simulated sunlight, achieving a photocurrent density of 10 mA cm at +0.13 V vs RHE. Furthermore, electrostatic incorporation of the thio-POM anion into a poly(3,4-ethylenedioxythiophene) (PEDOT) film is demonstrated to be efficient and straightforward to durably retain the at the interface of a micropyramidal silicon () photocathode. The thio-POM/PEDOT-modified photocathode is able to produce H under 1 Sun illumination at a rate of ca. 100 μmol cm h at 0 V vs RHE, highlighting the excellent performance of this photoelectrochemical system.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/jacs.9b03950DOI Listing
July 2019

A Series of Octahedral First-Row Transition-Metal Ion Complexes Templated by Wells-Dawson Polyoxometalates: Synthesis, Crystal Structure, Spectroscopic, and Thermal Characterizations, and Electrochemical Properties.

Inorg Chem 2018 Oct 10;57(19):11909-11919. Epub 2018 Sep 10.

Institut Lavoisier de Versailles , University of Versailles Saint-Quentin-en-Yvelines, UMR 8180 , 45 avenue des Etats-Unis , 78035 Versailles Cedex , France.

Three Wells-Dawson polyoxotungstates-based hybrid compounds of general formula [M(CHNO)][{M(CHNO)}(μ-PWO)]· nCHNO· n'HO [with M = Mn (1), Fe (2), Co (3) ; n = 2, 2, 3 and n' = 0, 0, 1, respectively] were synthesized at room temperature by a facile method and characterized by IR and H and P NMR spectroscopy studies, thermogravimetric analysis-differential scanning calorimetry thermal analyses, UV-vis, X-ray diffraction (XRD) powder and single-crystal XRD analyses, and cyclic voltammetry studies. From the X-ray study, it was established that the metal (M = Mn, Fe, Co) is located on an inversion center, being octahedrally coordinated to six dimethylformamide (DMF) molecules to form the complex cation [M(dmf)]. Also, in the dinuclear complex anion [{M(dmf)}(μ-PWO)], the M atoms are coordinated to five DMF molecules through the oxygen atoms, while the sixth coordination site is occupied by a terminal oxygen atom of the Wells-Dawson anion [PWO] that plays the role of a bridging ligand. The crystal components are connected through numerous weak C-H···O hydrogen bonds to construct a three-dimensional network. The UV-vis shows the two characteristic absorption bands for the three compounds at 266-268 and 297 nm. These two strong bands are attributed to the charge-transfer absorption band of Ot-W and Ob/c-W, respectively. Cyclic voltammetry study of compounds (1), (2), and (3) reveals at least two reduction reversible peaks ascribed to a Wells-Dawson cluster.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.inorgchem.8b01207DOI Listing
October 2018

Probing Dynamic Library of Metal-Oxo Building Blocks with γ-Cyclodextrin.

J Am Chem Soc 2018 09 4;140(36):11198-11201. Epub 2018 Sep 4.

Institut Lavoisier de Versailles, UVSQ, CNRS, Université Paris-Saclay , Versailles 78000 , France.

Formation of one of the most representative polyoxometalate (POM) archetypes, namely the Lindqvist anion MO with M = Mo or W, was considered as elusive in aqueous solution. Herein, we report on the host-guest stabilization of the MO species with M = Mo or W from aqueous solution using γ-cyclodextrin as trapping agent. The adduct {MO@γ-CD} reveals remarkable hydrolytic stability that offers new opportunities for exploring potentialities of molybdates or tungstates in the field of biology and medicine, when combined to CDs as efficient drug carrier/delivery agents.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/jacs.8b07525DOI Listing
September 2018

Host-Guest Binding Hierarchy within Redox- and Luminescence-Responsive Supramolecular Self-Assembly Based on Chalcogenide Clusters and γ-Cyclodextrin.

Chemistry 2018 Sep 30;24(51):13467-13478. Epub 2018 Jul 30.

Institut Lavoisier de Versailles, CNRS, UVSQ, Université Paris-Saclay, 45 avenue des Etats-Unis, 78035, Versailles, France.

Water-soluble salts of anionic [Re Q (CN) ] (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 [Re S (CN) ] interacts preferentially with the primary faces of the γ-CD while the bulkier clusters [Re Se (CN) ] and [Re Te (CN) ] 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 [Re S (CN) ] or to 1D "bamboo-like" columns with [Re Se (CN) ] and [Re Te (CN) ] 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.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/chem.201802102DOI Listing
September 2018

pH-Controlled One Pot Syntheses of Giant MoOS-Containing Seleno-Tungstate Architectures.

Inorg Chem 2018 Jan 15;57(1):56-63. Epub 2017 Dec 15.

Institut Lavoisier de Versailles, UMR CNRS 8180, UVSQ, University Paris-Saclay , 45 avenue des Etats-Unis, 78035 Versailles, France.

Self-assembly reactions of NaWO, SeO/SeO, and [MoO(μ-S)(HO)] give, depending on the pH value, two new large polyoxometalate complexes: i.e., [(γ-SeWO)(MoO(μ-S)(HO))] (1) isolated at pH 3.5 and [(γ-SeWO)(WO(HO))(WO)(WO)(MoO(μ-S)(HO))(MoO(μ-S)(SeO))] (2) isolated at pH 2. Both compounds were characterized in the solid state by single-crystal X-ray diffraction, EDX, elemental analysis, TGA, and FT-IR and in solution by ESI-MS and NMR.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.inorgchem.7b01644DOI Listing
January 2018

Nonconventional Three-Component Hierarchical Host-Guest Assembly Based on Mo-Blue Ring-Shaped Giant Anion, γ-Cyclodextrin, and Dawson-type Polyoxometalate.

J Am Chem Soc 2017 10 5;139(41):14376-14379. Epub 2017 Oct 5.

Institut Lavoisier de Versailles UMR 8180, UVSQ, Université Paris-Saclay , 78035 Versailles, France.

In this communication, we report on a noteworthy hybrid supramolecular assembly built from three functional components hierarchically organized through noncovalent interactions. The one-pot synthesis procedure leads to the formation of large Mo-blue ring-shaped anion {Mo}, which contains the supramolecular adduct based on the symmetric encapsulation of the Dawson-type [PWO] anion by two γ-cyclodextrin units. Such a nanoscopic onion-like structure, noted [PWO]@2γ-CD@{Mo} has been characterized by single-crystal X-ray diffraction, thus demonstrating the capability of the giant inorganic torus to develop relevant supramolecular chemistry, probing the strong affinity of the inner and outer faces of the γ-CD for the polyoxometalate surfaces. Furthermore, interactions and behavior in solution have been studied by multinuclear NMR spectroscopy, which supports specific interactions between γ-CD and POM units. Finally, the formation of this three-component hybrid assembly from one-pot procedure, in water and using nearly stoichiometric conditions, is discussed in terms of the driving forces orchestrating this highly efficient multilevel recognition process.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/jacs.7b08058DOI Listing
October 2017

Polyoxometalate, Cationic Cluster, and γ-Cyclodextrin: From Primary Interactions to Supramolecular Hybrid Materials.

J Am Chem Soc 2017 09 1;139(36):12793-12803. Epub 2017 Sep 1.

Institut Lavoisier de Versailles, UMR 8180, UVSQ, Université Paris-Saclay , 78035 Versailles, France.

Herein, we report on a three-component supramolecular hybrid system built from specific recognition processes involving a Dawson-type polyoxometalate (POM), [PWO], a cationic electron-rich cluster [TaBr(HO)], and γ-cyclodextrin (γ-CD). Such materials have been investigated using a bottom-up approach by studying the specific interactions between γ-CD and both types of inorganic units. Their ability to interact has been investigated in the solid state by single-crystal X-ray diffraction (XRD) and in solution using multinuclear NMR methods (including DOSY, EXSY, and COSY), electrospray ionization mass and UV-vis spectroscopies, electrochemistry, and isothermal titration calorimetry experiments. Single-crystal XRD analysis reveals that POM:γ-CD constitutes a highly versatile system which gives aggregates with 1:1, 1:2, and 1:3 stoichiometry. Surprisingly, these arrangements exhibit a common feature wherein the γ-CD moiety interacts with the Dawson-type POMs through its primary face. We present also the first structural model involving an octahedral-type metallic cluster with γ-CD. XRD study reveals that the cationic [TaBr(HO)] ion is closely embedded within two γ-CD units to give a supramolecular ditopic cation, suitable to be used as a linker within extended structure. Solution study demonstrates clearly that pre-associations exist in solution, for which binding constants and thermodynamic parameters have been determined, giving preliminary arguments about the chaotropic nature of the inorganic ions. Finally, both building blocks, i.e., the ditopic supramolecular cation {[TaBr(HO)]@2CD} and the Dawson-type anion, react together to give a three-component, well-ordered hybrid material derived either as a supramolecular hydrogel or single crystals. The solid-state structure shows an unprecedented helicoidal tubular chain resulting from the periodic alternation of POM and supramolecular cation, featuring short hydrogen-bonding contacts between the electron-poor POM and electron-rich cluster. The 1D tubular ionic polymer observed in the single crystals should make it possible to understand the long-range ordering observed within the hydrogel hybrid material. The supramolecular chemical complementarities between the γ-CD-based ditopic cation and POM open a wide scope for the design of hybrid materials that accumulate synergistic functionalities.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/jacs.7b07317DOI Listing
September 2017

High-field Mo and W static and MAS NMR study of polyoxometalates.

Magn Reson Chem 2017 Oct 11;55(10):902-908. Epub 2017 May 11.

ILV, UMR CNRS 8180, UVSQ, Versailles, 78035, Cedex, France.

The potential of high-field NMR to measure solid-state Mo and W 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.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/mrc.4601DOI Listing
October 2017

Two Compartmentalized Inner Receptors for the Tetramethylammonium Guest within a Keplerate-Type Capsule.

Inorg Chem 2016 Sep 6;55(18):9368-76. Epub 2016 Sep 6.

Institut Lavoisier de Versailles, UMR CNRS 8180, University of Versailles Saint Quentin en Yvelines, University Paris-Saclay , 45 avenue des Etats-Unis, 78035 Versailles, France.

The host-guest interactions between the spherical porous Keplerate anion, [Mo132O372(CH3CO2)30(H2O)72](42-) (abbreviated {Mo132}) and the tetramethylammonium cation have been investigated extensively by one- and two-dimensional (EXSY, ROESY, and DOSY) and variable-temperature NMR. Evidence of two inner receptor sites specific for a NMe4(+) guest appears consistent with a quite striking compartmentalization phenomenon. ROESY NMR analyses showed that both sites exhibit a close spatial proximity with the hanging inner acetate groups, while a quantitative EXSY study revealed that these two sites are differentiated by their exchange rates. These NMR data support the hypothesis that these two inner sites could be delimited by the hanging inner acetate groups forming triangular (S1) or pentagonal (S2) hydrophobic pockets on the inner side of the capsule wall. Furthermore, the stability constants associated with the trapping process of the NMe4(+) guest on both the S1 and S2 sites have been determined, showing that the stability constant of the S1 sites decreases significantly as the concentration of the capsule increases gradually, while that of the S2 sites remains nearly unaffected. Such an observation has been interpreted as a result of the plugging process of the {Mo9O9} pores by the counterions NH4(+), which causes unfavorable electrostatic interactions for the NMe4(+) coordination on the proximal S1 site. Finally, the thermodynamic parameters of the NMe4(+) transfer from the solvated situation to the interior of the capsule were estimated from variable-temperature NMR experiments that provide the split of the global process into two successive events corresponding to the plugging and transfer across the inorganic shell.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.inorgchem.6b01516DOI Listing
September 2016

Tunable Keplerate Type-Cluster "Mo132 " Cavity with Dicarboxylate Anions.

Chemistry 2015 Sep 29;21(38):13311-20. Epub 2015 Jul 29.

Institut Lavoisier de Versailles, UMR 8180, University of Versailles, 45 avenue des Etats-Unis, 78035 Versailles (France).

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 AcO -
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/chem.201406648DOI Listing
September 2015

Hydrophobic effect as a driving force for host-guest chemistry of a multi-receptor Keplerate-type capsule.

J Am Chem Soc 2015 May 23;137(17):5845-51. Epub 2015 Apr 23.

†Institut Lavoisier de Versailles UMR 8180, Université de Versailles Saint-Quentin, 78035 Versailles, France.

The effectiveness of the interactions between various alkylammonium cations and the well-defined spherical Keplerate-type {Mo132} capsule has been tracked by (1)H DOSY NMR methodology, revealing a strong dependence on the self-diffusion coefficient of the cationic guests balanced between the solvated and the plugging situations. Analysis of the data is fully consistent with a two-site exchange regime involving the 20 independent {Mo9O9} receptors of the capsule. Furthermore, quantitative analysis allowed us to determine the stability constants associated with the plugging process of the pores. Surprisingly, the affinity of the capsule for a series of cationic guests increases continuously with its apolar character, as shown by the significant change of the stability constant from 370 to 6500 for NH4(+) and NEt4(+), respectively. Such observations, supported by the thermodynamic parameters, evidence that the major factor dictating selectivity in the trapping process is the so-called "hydrophobic effect". Computational studies, using molecular dynamics simulations, have been carried out in conjunction with the experiments. Analysis of the radial distribution functions g(r) reveals that NH4(+) and NMe4(+) ions behave differently in the vicinity of the capsule. The NH4(+) ions do not exhibit well-defined distributions when in close vicinity. In contrast, the NMe4(+) ions displayed sharp distributions related to different scenarios, such as firmly trapped or labile guest facing the {Mo9O9} pores. Together, these experimental and theoretical insights should aid in the exploitation of these giant polyoxometalates in solution for various applications.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/jacs.5b01526DOI Listing
May 2015

Synthesis, characterization, and tuning of the liquid crystal properties of ionic materials based on the cyclic polyoxothiometalate [{Mo4O4S4(H2O)3(OH)2}2(P8W48O184)](36-).

Soft Matter 2015 Feb;11(6):1087-99

Institut Lavoisier de Versailles, UMR 8180, University of Versailles, 45 Avenue des Etats-Unis, 78035 Versailles, France.

A series of compounds resulting from the ionic association of a nanoscopic inorganic cluster of formula [K2NaxLiy{Mo4O4S4(OH)2(H2O)3}2(HzP8W48O184)]((34-x-y-z)-), 1, with several organic cations such as dimethyldioctadecylammonium DODA(+), trimethylhexadecylammonium TMAC16(+), alkylmethylimidazoliums mimCn(+) (n = 12-20) and alkyl-dimethylimidazoliums dmimCn(+) (n = 12 and 16) was prepared and characterized in the solid state by FT-IR, EDX, Elemental analysis, TGA and solid state NMR. The solid state NMR experiments performed on (1)H, (13)C and (31)P nuclei evidenced the interactions between the cations and 1 as well as the organization of the alkyl chains of the cations within the solid. Polarized optical microscopy, DSC and SA-XRD experiments implicated mesomorphic phases for DODA(+) and mimCn(+) salts of 1. The crystallographic parameters were determined and demonstrated that the inter-lamellar spacing could be controlled upon changing the length of the alkyl chain, a very interesting result if we consider the huge size of the inorganic cluster 1 and the simple nature of the cations.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c4sm02551bDOI Listing
February 2015

Tracking "apolar" NMe4+ ions within two polyoxothiomolybdates that have the same pores: smaller clathrate and larger highly porous clusters in action.

Chemistry 2014 Mar 12;20(11):3097-105. Epub 2014 Feb 12.

Nikolaev Institute of Inorganic Chemistry, Siberian Branch of the Russian Academy of Sciences, Novosibirsk 630090 (Russia).

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. (1)H 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 (1)H 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.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/chem.201303719DOI Listing
March 2014

Tuning the electrocatalytic hydrogen evolution reaction promoted by [Mo2O2S2]-based molybdenum cycles in aqueous medium.

Dalton Trans 2013 Apr;42(14):4848-58

Institut Lavoisier de Versailles, UMR 8180, Université de Versailles Saint-Quentin en Yvelines, 45 avenue des Etats-Unis, 78035 Versailles Cedex, France.

We report the syntheses and characterizations, in the solid state and in solution, of three new cyclic polyoxothiomolybdates self-assembled around 2,5-dimethylterephthalate (DMT) and 2,5-bis(trifluoromethyl)terephthalate (DFMT) ligands, namely [Mo12DMT](2-), [Mo12DFMT](2-) and [Mo16DFMT](2-). A series of these two Mo12-compounds completed by the two Mo12-compounds obtained with 2,3,5,6-tetramethylterephthalate and trimesate ligands offer the opportunity to compare their electro-catalytic properties for reduction of protons into hydrogen. The ability of these compounds to promote the reduction of protons into hydrogen in aqueous medium is evidenced and the influence of the embedded ligand is highlighted, thus allowing proposal of a mechanism for the hydrogen evolution reaction catalyzed by these clusters.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c2dt32447dDOI Listing
April 2013

A further step towards tuning the properties of metal-chalcogenide nanocapsules by replacing skeletal oxide by sulphide ligands.

Dalton Trans 2013 Jan 12;42(2):330-3. Epub 2012 Nov 12.

Fakultät für Chemie, Universität Bielefeld, Postfach 100131, 33501 Bielefeld, Germany.

Addition of [Mo(2)(V)O(2)(μ-O)(μ-S)(aq)](2+) linker-type units to a solution/dynamic library containing tungstates results via the formation of the complementary pentagonal {(W)W(5)} units logically in the self-assembly of a mixed oxide/sulphide {W(VI)(72)Mo(V)(60)}-type Keplerate, thereby demonstrating the ability to tune the capsule's skeletal softness (the (μ-O)(2) and (μ-S)(2) scenarios are known) and providing options to influence differently important capsule-substrate interactions.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c2dt32247aDOI Listing
January 2013

Cubic box versus spheroidal capsule built from defect and intact pentagonal units.

J Am Chem Soc 2012 Nov 14;134(47):19342-5. Epub 2012 Nov 14.

Institut Lavoisier de Versailles UMR 8180, Université de Versailles Saint-Quentin, 78035 Versailles, France.

The high-nuclearity polyoxothiomolybdate [H(8)Mo(84)S(48)O(188)(H(2)O)(12)(CH(3)COO)(24)](32-) has been prepared and characterized by single-crystal X-ray crystallography and (1)H NMR, IR, Raman, and UV-vis spectroscopy. The solid-state structure reveals an unprecedented and intriguing arrangement consisting of a nanoscaled anionic cube. The surprisingly open structure of this {Mo(84)}-type cubic box features a large inner void that is accessible via its six open square faces with diameters of ca. 9 Å. Importantly, this molecular system appears to be highly functionalizable because of the presence of 24 exposed exchangeable acetate ligands.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/ja309302yDOI Listing
November 2012

A building block strategy to access sulfur-functionalized polyoxometalate based systems using {Mo2S2O2} and {Mo3S4} as constitutional units, linkers or templates.

Chem Soc Rev 2012 Nov 20;41(22):7335-53. Epub 2012 Aug 20.

Institut Lavoisier de Versailles, UMR 8180, Université de Versailles Saint Quentin, 45 Avenue des Etats-Unis, 78035 Versailles, France.

The present tutorial review reports on the synthetic approaches for the formation of "polyoxothiometalate" compounds with special emphasis on the unique reactivity of the preformed sulfur-containing cationic building blocks {Mo(2)O(2)S(2)}(2+) and {Mo(3)S(4)}(4+) toward polyoxometalate building blocks. Such simple chemical systems, based on chemical and structural complementarities between ionic reactive moieties have led to the synthesis of a series of relevant clusters with unrivalled large nuclearity structural arrangements, such as loops, triangles, squares and boxes. Specific reaction parameters and considerations will be pointed out showing that a deliberate pure inorganic supramolecular chemistry based on weak interactions, flexibility and dynamic is possible with polyoxometalates.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c2cs35145eDOI Listing
November 2012

Syntheses, characterizations and properties of [Mo2O2S2]-based oxothiomolybdenum wheels incorporating bisphosphonate ligands.

Dalton Trans 2012 Sep 7;41(33):9955-63. Epub 2012 Jun 7.

Institut Lavoisier de Versailles, UMR 8180, Université de Versailles Saint-Quentin en Yvelines, 45 avenue des Etats-Unis, 78035 Versailles Cedex, France.

We report the syntheses and characterizations of the first polyoxothiometalate complexes isolated from the reaction of the oxothiocationic [Mo(V)(2)O(2)S(2)](2+) precursor and bisphosphonate ligands H(2)O(3)PCR(OH)PO(3)H(2) (R = C(4)H(5)N(2), zoledronic acid; R = C(3)H(6)NH(2), alendronic acid). [(Mo(2)O(2)S(2)(H(2)O))(4)(O(3)PC(O)(C(4)H(6)N(2))PO(3))(4)](8-) (Mo(8)S(8)(Zol)(4)) and [(Mo(2)O(2)S(2)(H(2)O))(4)(O(3)PC(O)(C(3)H(6)NH(3))PO(3))(4)](8-) (Mo(8)S(8)(Ale)(4)) contain four Mo(V) dimers connected via bisphosphonate ligands. These compounds offer a unique opportunity to compare the structures and properties of cyclic compounds obtained with [Mo(2)O(2)S(2)](2+) and with [Mo(2)O(4)](2+). The oxothio compounds appear less stable in solution than the oxo analogue, confirming the higher lability and versatility of [Mo(2)O(2)S(2)]-based compounds compared to [Mo(2)O(4)]-based POMs. Multinuclear and multidimensional solid-state NMR studies were carried out to complement X-ray diffraction analysis. Information on short-range interactions, dynamic behaviors, and local disorder within the crystalline materials are therefore reported. Furthermore, the electrocatalytic properties of Mo(8)S(8)(Ale)(4) and of the analogous [(Mo(2)O(4)(H(2)O))(4)(O(3)PC(O)(C(3)H(6)NH(3))PO(3))(4)](8-) (Mo(8)O(8)(Ale)(4)) immobilized onto the surface of a glassy carbon electrode were studied, thus evidencing the ability of [Mo(2)O(2)S(2)]-based cycles to promote the reduction of protons into hydrogen, whereas the oxo analogue appeared inactive.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c2dt30534hDOI Listing
September 2012

{AsW9O33}-{Mo3S4} based polyoxometalates including a metal-metal bond with Pd or Ni. Synthesis, structure and studies in solution.

Dalton Trans 2012 Mar 30;41(11):3174-84. Epub 2012 Jan 30.

University of Versailles Saint Quentin, Institute Lavoisier of Versailles, ILV, UMR CNRS 8180, Versailles, France.

Heterometallic cuboidal clusters [Mo(3)S(4)M(H(2)O)(9)Cl](3+) M = Pd or Ni react with the trivacant [AsW(9)O(33)](9-) anion to give tetramodular complexes [(H(2)AsW(9)O(33))(4){Mo(3)S(4)M(H(2)O)(5)}(2)](20-) (M = Pd for anion 2 and M = Ni for anion 3) in good yield. Both anions crystallized as single crystals of potassium salts to give K-2 and K-3 salts which have been characterized structurally by X-ray diffraction. Both compounds are isomorphous and the anions 2 and 3 are described as two dimeric moeties, associated by internal hydrogen bonds, electrostatic interactions involving four outer potassium ion and coordination bonds within a central {M(2)S(2)} unit containing a M-M metallic bond. Studies in solution reveal that the dimeric association is maintained in solution in the 2 × 10(-4)-2 × 10(-3) mol L(-1) range. Conversely, in the presence of exogeneous ligands, such as iodide or pyridine the UV-vis data are consistent with the dissociation of the anion 2 into monomer through a Pd-L coordination bond (L = I(-) or Py). Furthermore, (183)W NMR spectrum of 2 shows that molecular structure of 2 is retained in solution. Elemental analysis and IR are also supplied. Electrochemical behavior of 2 and 3 are given and compared with the Pd or Ni free parent anion. The CVs are dominated mainly by irreversible reduction or oxidation processes, where the peak potentials appear dependent upon the ionic charge of the complex. However, the CV of the Pd-containing anion (2) is consistent with the deposition of Pd metal at the electrode, which gives rise to an oxidation process into palladium oxide.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c2dt11420hDOI Listing
March 2012

Oxothiomolybdenum derivatives of the superlacunary crown heteropolyanion {P8W48}: structure of [K4{Mo4O4S4(H2O)3(OH)2}2(WO2)(P8W48O184)]30– and studies in solution.

Inorg Chem 2012 Feb 23;51(4):2349-58. Epub 2012 Jan 23.

Institut Lavoisier de Versailles, UMR 8180, University of Versailles, 45 avenue des Etats-Unis, 78035 Versailles, France.

Reaction of the cyclic lacunary [H(7)P(8)W(48)O(184)](33-) anion (noted P(8)W(48)) with the [Mo(2)S(2)O(2)(H(2)O)(6)](2+) oxothiocation led to two compounds, namely, [K(4){Mo(4)O(4)S(4)(H(2)O)(3)(OH)(2)}(2)(WO(2))(P(8)W(48)O(184))](30-) (denoted 1) and [{Mo(4)O(4)S(4)(H(2)O)(3)(OH)(2)}(2)(P(8)W(48)O(184))](36-) (denoted 2), which were characterized in the solid state and solution. In the solid state, the structure of [K(4){Mo(4)O(4)S(4)(H(2)O)(3)(OH)(2)}(2)(WO(2))(P(8)W(48)O(184))](30-) reveals the presence of two disordered {Mo(4)O(4)S(4)(H(2)O)(3)(OH)(2)}(2+) "handles" connected on both sides of the P(8)W(48) ring. Such a disorder is consistent with the presence of two geometrical isomers where the relative disposition of the two {Mo(4)O(4)S(4)(H(2)O)(3)(OH)(2)}(2+) handles are arranged in a perpendicular or parallel mode. Such an interpretation is fully supported by (31)P and (183)W NMR solution studies. The relative stability of both geometrical isomers appears to be dependent upon the nature of the internal alkali cations, i.e., Na(+) vs K(+), and increased lability of the two {Mo(4)O(4)S(4)(H(2)O)(3)(OH)(2)}(2+) handles, compared to the oxo analogous, was clearly identified by significant broadening of the (31)P and (183)W NMR lines. Solution studies carried out by UV-vis spectroscopy showed that formation of the adduct [{Mo(4)O(4)S(4)(H(2)O)(3)(OH)(2)}(2)(P(8)W(48)O(184))](36-) occurs in the 1.5-4.7 pH range and corresponds to a fast and quantitative condensation process. Furthermore, (31)P NMR titrations in solution reveal formation of the "monohandle" derivative [{Mo(4)O(4)S(4)(H(2)O)(3)(OH)(2)}(P(8)W(48)O(184))](38-) as an intermediate prior to formation of the "bishandle" derivatives. Furthermore, the electrochemical behavior of [{Mo(4)O(4)S(4)(H(2)O)(3)(OH)(2)}(2)(P(8)W(48)O(184))](36-) was studied in aqueous medium and compared with the parent anion P(8)W(48).
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/ic202346rDOI Listing
February 2012

Polyoxometalates paneling through {Mo2O2S2} coordination: cation-directed conformations and chemistry of a supramolecular hexameric scaffold.

J Am Chem Soc 2012 Jan 17;134(3):1724-37. Epub 2012 Jan 17.

Institut Lavoisier de Versailles, UMR 8180, Université de Versailles Saint Quentin, 45 Avenue des Etats-Unis, 78035 Versailles, France.

The chemical system based on the [Mo(2)O(2)S(2)(OH(2))(6)](2+) aqua cation (noted L) and the trivacant [AsW(9)O(33)](9-) polyoxometalate (noted POM) has been investigated. Depending upon the ionic strength and the nature of the alkali cations, these complementary components assemble to yield three different architectures derived as hexamer (1), tetramer (2), and dimer (3). This series of clusters displays the same stoichiometry {POM(6)L(9)}(36-), {POM(4)L(6)}(24-), and {POM(2)L(3)}(12-) for 1, 2, and 3, respectively, and their conditions of formation differ mainly by the nature and the concentration of the alkali cation (from Li to Cs). Structural characterizations of 1 reveal a large hexameric supramolecular scaffold (about 25 Å in diameter), which encloses a large internal hole (about 200 Å(3)) filled by water molecules and alkali cations (Na(+) or K(+)). The hexameric scaffold 1 exhibits a rare flexibility property evidenced in the solid state by two distinct conformations, either eclipsed (1a) or staggered-off (1b). Both conformations appear clearly separated by a large twist angle (~40°) and depend mainly on the composition of the internal hole. Structure of anion 2 shows a tetrahedral arrangement where the four POM units and the six connecting {Mo(2)O(2)S(2)} linkers are located at the corners and at the edges, respectively. The structure of anion 3 corresponds to the simplest arrangement, described as a dimeric association of two POM units linked by three {Mo(2)S(2)O(2)} pillars. Stability of the hexameric scaffold has been investigated in solution by (183)W and (39)K NMR and by UV-vis, showing that stability of 1 depends strongly on the proportion of potassium ions, which interfere through host-guest exchange. Density functional methodology (DFT) has been applied to compute the geometries and energies of dimer (3), tetramer (2) and hexamer (1) based on {AsW(9)O(33)} (POM) and {Mo(2)O(2)S(2)} (L) units. Calculations tend to show that internal cations act as "glue" to maintain the POM units connected through the conformationally inward-directed {Mo(2)O(2)S(2)} linkers.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/ja2090383DOI Listing
January 2012