A Strategy for the Analysis of Chiral Polyoxotungstates by Multinuclear (³¹P, ¹⁸³W) NMR Spectroscopy Applied to the Assignment of the ¹⁸³W NMR Spectra of α₁-[P₂W₁₇O₆₁]^10- and α₁-[YbP₂W₁₇O₆₁]^7-

This paper describes the complete assignment of the 183W NMR spectra of the chiral polyoxometalates α1-[P2W17O61]10- and α1-[YbP2W17O61]7- in aqueous solution. These spectra display each 17 lines of equal intensity with a relatively narrow chemical shift distribution. The identification of signals is based on selective 31P−183W decoupling and recognition of particular sets of coupling constants for tungsten atoms around the lacunary site. Further assignment is obtained by 183W 2D-COSY NMR experiments. We demonstrate herewith a new way for the unambiguous assignment of 183W NMR spectra of polyoxotungstates without any symmetry elements or tungsten atoms in special positions. This way relies on the correlation of the magnitude of 2JW-W coupling constants with the geometry of oxo-bridges in polyoxotungstates. These results open the way to monitor interaction sites of chiral polyoxotungstates with organic ligands

A General Strategy for Ligation of Organic and Biological Molecules to Dawson and Keggin Polyoxotungstates

The copper-catalyzed azide/alkyne cycloaddition (click chemistry) is used for the first time in polyoxometalate chemistry to graft any kind of organics (lipophilic, water-soluble, biologically relevant) to polyoxotungstates to generate hybrids. The method is not limited by solvent matching between the polyoxometallic platforms and the organic substrates

Water Dissociation on α₁-Hafnium and Ytterbium Substituted Dawson Polyoxotungstates: A Density Functional Theory Study

Density functional theory (DFT) calculations were devised to get insight into Lewis acidic catalysis by POMs, especially on the intriguing activation of complexed water molecules that was observed in some experimental cases. Computationally, it appears that deprotonation is feasible with [α1-Hf(H2O)P2W17O61]6-, but not with [α1-Yb(H2O)P2W17O61]7-. This reflects the difference of the electronic structures (diamagnetic for hafnium POM, paramagnetic for ytterbium POM). From a mechanistical point of view, indirect Brønsted catalysis cannot be excluded in the hafnium case, especially for Mannich reactions. But our calculations show that catalysis by [α1-Yb(H2O)P2W17O61]7- (and presumably all the lanthanide series) proceeds through direct complexation of the substrates to the POM

Precise Rate Control of Pseudorotaxane Dethreading by pH-Responsive Selectively Functionalized Cyclodextrins

A family of cyclodextrins functionalized with zero, one, two, or six amines was shown to control the rate of their threading and dethreading on a molecular axle depending on the pH and their substitution pattern. The originality of this system lies in the rate control of the switch by operating the stimulus directly on the macrocycle

Discrete Covalent Organic–Inorganic Hybrids: Terpyridine Functionalized Polyoxometalates Obtained by a Modular Strategy and Their Metal Complexation

The rational design and synthesis of organic–inorganic hybrids as functional molecular materials relies on both the careful conception of building-blocks and the strategy for their assembly. Three families of trialkoxo polyoxometalates (Lindqvist 2, Anderson 3, Dawson 4) grafted with remote terpyridine coordination sites have been synthesized to extend the available building-blocks. These new units can be combined with metal complexes that play a role as (i) chromophores toward charge-separated systems in light-harvesting devices and (ii) coordination motifs for metal-directed self-assembly toward multifunctional molecular hybrid materials. The X-ray crystal structures of polyoxometalate-terpyridine hybrids indicate distances of 21 Å and 19 Å between the two terpyridyl coordination sites in 2 and 3, respectively, with angles between the coordination vectors of 180° and 177.4°, respectively. Lindqvist 2 displays a reduction at −0.52 V vs SCE while Anderson 3 exhibits one reversible oxidation attributed to Mn(III)/Mn(IV) (+0.75 V vs SCE) and a broad wave at −1.28 V vs SCE assigned to the Mn(III)/Mn(II) reduction. Dawson 4 displays several processes on a wide range of potentials (+0.5 to −2.0 V vs SCE) centered on V(V), W(VI) and the organic ligand in order of decreasing potentials. The grafted terpyridine ligands in Anderson 3 and Dawson 4 were successfully coordinated to {PdCl}+ and {RuCl3} moieties, respectively. The polyoxometalates and transition metal complexes retain their intrinsic properties in the final assemblies

Discrete Covalent Organic–Inorganic Hybrids: Terpyridine Functionalized Polyoxometalates Obtained by a Modular Strategy and Their Metal Complexation

The rational design and synthesis of organic–inorganic hybrids as functional molecular materials relies on both the careful conception of building-blocks and the strategy for their assembly. Three families of trialkoxo polyoxometalates (Lindqvist 2, Anderson 3, Dawson 4) grafted with remote terpyridine coordination sites have been synthesized to extend the available building-blocks. These new units can be combined with metal complexes that play a role as (i) chromophores toward charge-separated systems in light-harvesting devices and (ii) coordination motifs for metal-directed self-assembly toward multifunctional molecular hybrid materials. The X-ray crystal structures of polyoxometalate-terpyridine hybrids indicate distances of 21 Å and 19 Å between the two terpyridyl coordination sites in 2 and 3, respectively, with angles between the coordination vectors of 180° and 177.4°, respectively. Lindqvist 2 displays a reduction at −0.52 V vs SCE while Anderson 3 exhibits one reversible oxidation attributed to Mn(III)/Mn(IV) (+0.75 V vs SCE) and a broad wave at −1.28 V vs SCE assigned to the Mn(III)/Mn(II) reduction. Dawson 4 displays several processes on a wide range of potentials (+0.5 to −2.0 V vs SCE) centered on V(V), W(VI) and the organic ligand in order of decreasing potentials. The grafted terpyridine ligands in Anderson 3 and Dawson 4 were successfully coordinated to {PdCl}+ and {RuCl3} moieties, respectively. The polyoxometalates and transition metal complexes retain their intrinsic properties in the final assemblies

Discrete Covalent Organic–Inorganic Hybrids: Terpyridine Functionalized Polyoxometalates Obtained by a Modular Strategy and Their Metal Complexation

The rational design and synthesis of organic–inorganic hybrids as functional molecular materials relies on both the careful conception of building-blocks and the strategy for their assembly. Three families of trialkoxo polyoxometalates (Lindqvist 2, Anderson 3, Dawson 4) grafted with remote terpyridine coordination sites have been synthesized to extend the available building-blocks. These new units can be combined with metal complexes that play a role as (i) chromophores toward charge-separated systems in light-harvesting devices and (ii) coordination motifs for metal-directed self-assembly toward multifunctional molecular hybrid materials. The X-ray crystal structures of polyoxometalate-terpyridine hybrids indicate distances of 21 Å and 19 Å between the two terpyridyl coordination sites in 2 and 3, respectively, with angles between the coordination vectors of 180° and 177.4°, respectively. Lindqvist 2 displays a reduction at −0.52 V vs SCE while Anderson 3 exhibits one reversible oxidation attributed to Mn(III)/Mn(IV) (+0.75 V vs SCE) and a broad wave at −1.28 V vs SCE assigned to the Mn(III)/Mn(II) reduction. Dawson 4 displays several processes on a wide range of potentials (+0.5 to −2.0 V vs SCE) centered on V(V), W(VI) and the organic ligand in order of decreasing potentials. The grafted terpyridine ligands in Anderson 3 and Dawson 4 were successfully coordinated to {PdCl}+ and {RuCl3} moieties, respectively. The polyoxometalates and transition metal complexes retain their intrinsic properties in the final assemblies

Spanning Pairs of Rh₂(acetate)₄ Units with Ru(II) Complexes

A synthetic route to linear pairs of Rh2 “paddlewheel” dimers bridged by Ru(II) complexes is presented. A bis(4′-(4-carboxyphenyl)-terpyridine)Ru(II) complex spans two Rh2 dimers and displays a 26 Å separation between the dimers. Increased electronic interaction is found for the dimer of dimers without the phenyl groups using bis(4′-(4-carboxy)-terpyridine)Ru(II) as the bridging complex

Carbonyl-Inserted Organo-Hybrids of a Dawson-Type Phosphovanadotungstate: Scope and Chemoselective Oxidation Catalysis

The Dawson-type polyoxometalate (POM) [P2V3W15O62]9– is a prototype for inclusion of carbonyls of amides, ureas, carbamates, and thiocarbamates into polyoxometallic structures. The carbonyl-inserted POMs catalyze the oxidation of sulfides. Chemoselectivity depends primarily on the proton content of the POM, but it is also influenced by the organic substituent

Pd-Containing Organo­polyoxo­metalates Derived from Dawson Polyoxo­metalate [P₂W₁₅V₃O₆₂]^9–: Lewis Acidity and Dual Site Catalysis

Grafting of a palladium complex to the Dawson vanado­tungstate polyanion [P₂W₁₅V₃O₆₂]^9– via an organic ligand generates a large family of pincer-type hybrid polyoxometalates. The palladium-POM derivatives have dual catalytic properties. Unlike their parent inorganic polyanions, they catalyze allylations while retaining their oxidant character, which leads to single-pot dual site catalysis. This opens a new route for multicatalytic reactions