Polyoxometalate Anions Research Articles

The interaction on HSA and the antibacterial activity from four polyoxometalate hybrids based on berberine

Four organic-polyoxometalate hybrids BR4[SiW12O40] (BR–SiW), BR3[PMo12O40] (BR–PMo), BR4K[EuSiW11O40]·2H2O (BR–EuSiW) and BR6Na3[EuW10O36] (BR–EuW) were fabricated by the polyoxometalates (POMs) anions and berberine cations (BR) noted for the alkaloids in traditional Chinese herbal medicine. These hybrids have been characterized and confirmed. The interaction between hybrids and human serum albumin (HSA) was investigated in a buffer solution (pH 7.4) using ultraviolet–visible light absorption and fluorescence techniques. The classical Stern–Volmer equation was used to analyze the fluorescence quenching at three temperatures (296, 303 and 310 K), and the static quenching mechanism for interaction was proposed. The Thermodynamic parameters, enthalpy, entropy change, and Gibbs free energy of hybrids interacting on HSA were calculated by Scatchard equation. The results indicated that therewas one binding site on the protein and BR–POMs all showed stronger binding force than that of raw materials. Synchronous fluorescence results showed that the binding sites of BR–POMs and HSA were not effectively affected the surrounding microenvironment. The following antibacterial experiments implied that inhibitory effect of hybrids were synergistic effect from organic active ingredient and POMs but the simple combination. All these data were prepared for further research on biology.

Synthesis, Characterization, and Catalytic Performance of Modified Keggin‐type Calix[6]arene‐like Polyoxometalates

AbstractTwo modified Calix[6]arene‐like polyoxometalates of the Keggin type with similar structures were synthesized under hydrothermal conditions by H3PMo12O40. H3PW12O40, 4H‐1,2,4‐triazol‐3‐amine (3‐atrz) and copper ions were used as precursors, respectively, bridging organic ligand and transition metals. The result of single‐crystal X‐ray diffraction and elemental analysis showed that the structural formulas of the two crystalline compounds were: [2(C6H12N12Cu3PW12O40)] (3‐atrz‐Cu‐PW12), and [2(C6H12N12Cu3PMo12O40)] ⋅ 0.5H2O (3‐atrz‐Cu‐PMo12). They were composed of two classic Keggin‐type polyoxometalate anions and six [Cu(C2H4N4)]+ coordination polymers similar to Calix[6]arene. The catalytic studies represented that the two heterogeneous catalysts catalyzed the oxidation of iodide ions in hydrogen peroxide. The catalytic reaction of 3‐atrz‐Cu‐PW12 only took 30 min and 15 s to complete the reaction. The rate of iodine generation was 6.86×10−7 mol L−1 s−1. The 3‐atrz‐Cu‐PMo12 catalytic reaction needed only 1 min and 51 s, in which the rate of iodine generation was 1.126×10−5 mol L−1 s−1. The catalytic reaction rate of 3‐atrz‐Cu‐PMo12 was 16.35 times higher than 3‐atrz‐Cu‐PW12. Both catalysts were reused nine times, and the conversion rate was still 99.96 %, showing excellent catalytic activity and repeatability.

Counteranion-induced structural isomerization of phosphine-protected PdAu8 and PtAu8 clusters

Controlling the geometric structures of metal clusters through structural isomerization allows for tuning of their electronic state. In this study, we successfully synthesized butterfly-motif [PdAu8(PPh3)8]2+ (PdAu8-B, B means butterfly-motif) and [PtAu8(PPh3)8]2+ (PtAu8-B) by the structural isomerization from crown-motif [PdAu8(PPh3)8]2+ (PdAu8-C, C means crown-motif) and [PtAu8(PPh3)8]2+ (PtAu8-C), induced by association with anionic polyoxometalate, [Mo6O19]2– (Mo6) respectively, whereas their structural isomerization was suppressed by the use of [NO3]– and [PMo12O40]3– as counter anions. DR-UV-vis-NIR and XAFS analyses and density functional theory calculations revealed that the synthesized [PdAu8(PPh3)8][Mo6O19] (PdAu8-Mo6) and [PtAu8(PPh3)8][Mo6O19] (PtAu8-Mo6) had PdAu8-B and PtAu8-B respectively because PdAu8-Mo6 and PtAu8-Mo6 had bands in optical absorption at the longer wavelength region and different structural parameters characteristic of the butterfly-motif structure obtained by XAFS analysis. Single-crystal and powder X-ray diffraction analyses revealed that PdAu8-B and PtAu8-B were surrounded by six Mo6 with rock salt-type packing, which stabilizes the semi-stable butterfly-motif structure to overcome high activation energy for structural isomerization.

Hydroxylated Polyoxometalate with Cu(II)- and Cu(I)-Aqua Complexes: A Bifunctional Catalyst for Electrocatalytic Water Splitting at Neutral pH.

A sole inorganic framework material [Li(H2O)4][{CuI(H2O)1.5} {CuII(H2O)3}2{WVI12O36(OH)6}]·N2·H2S·3H2O (1) consisting of a hydroxylated polyoxometalate (POM) anion, {WVI12O36(OH)6}6-, a mixed-valent Cu(II)- and Cu(I)-aqua cationic complex species, [{CuI(H2O)1.5}{CuII(H2O)3}2]5+, a Li(I)-aqua complex cation, and three solvent molecules, has been synthesized and structurally characterized. During its synthesis, the POM cluster anion gets functionalized with six hydroxyl groups, i.e., six WVI-OH groups per cluster unit. Moreover, structural and spectral analyses have shown the presence of H2S and N2 molecules in the concerned crystal lattice, formed from "sulfate-reducing ammonium oxidation (SRAO)". Compound 1 functions as a bifunctional electrocatalyst exhibiting oxygen evolution reaction (OER) by water oxidation and hydrogen evolution reaction (HER) by water reduction at the neutral pH. We could identify that the hydroxylated POM anion and copper-aqua complex cations are the functional sites for HER and OER, respectively. The overpotential, required to achieve a current density of 1 mA/cm2 in the case of HER (water reduction), is found to be 443 mV with a Faradaic efficiency of 84% and a turnover frequency of 4.66 s-1. In the case of OER (water oxidation), the overpotential needed to achieve a current density of 1 mA/cm2 is obtained to be 418 mV with a Faradaic efficiency of 80% and turnover frequency of 2.81 s-1. Diverse electrochemical controlled experiments have been performed to conclude that the title POM-based material functions as a true bifunctional catalyst for electrocatalytic HER as well as OER at the neutral pH without catalyst reconstruction.

Cover Feature: Importance of Electron Mediator Transparency: Photocatalytic Hydrogen Production from Polyoxometalate using Dye‐double‐layered Photocatalysts (ChemCatChem 4/2023)

The Cover Feature shows the photocatalytic hydrogen production by dual Ru(II)-dye sensitized layered niobate oxide with intercalated Pt cocatalyst in the presence of redox-reversible M-substituted polyoxometalate anions (M-POM, M = VIV, MnII). In their Research Article, A. Kobayashi and co-workers found that the photocatalytic activity is remarkably higher in MnII-POM aq. than that in VIV-POM aq. despite their comparable redox potentials. Their experimental results suggest that the visible-light transparency of surface-immobilized M-POM is the key factor for the photocatalytic H2 production activity. More information can be found in the Research Article by A. Kobayashi and co-workers.

Dynamic co-assembly behaviors of polyoxometalates and giant surfactants in dual solvents

Inorganic-organic hybridization is a widely used method to develop new functional materials involving polyoxometalates (POMs), affording them with unique synergistic physical and chemical properties. As one of the core topics in hybrid materials, the study of their assembly structures is critical for the optimization of their performances.In the present work, dynamic co-assembly behaviors of several giant surfactants XPOSS-PS (X, POSS and PS denote different polar groups, polyhedral oligomeric silsesquioxane and polystyrene, respectively) and Keggin-type silicotungstic acid H4SiW12O40 (H4SiW for short) were investigated. We designed and synthesized three series of giant surfactants that possess heads bearing cationic (NPOSS-PS, N for ammonium group), neutral (DPOSS-PS, D for dihydroxyl group) and anionic charges (APOSS-PS, A for carboxylic acid group), respectively. The different charge types of POSS heads lead to different electrostatic interactions with the anionic POM clusters, resulting in different co-assembly structures in dual mixed solvents. Moreover, we found the POM's loading content and PS chain length are another two important factors that can determine the morphology of co-assembly structures. This work expands the scope of co-assembled structures of POM-based hybrid materials, and provides a platform for the study of the basic physical principles of their co-assembly behaviors.

Polyoxometalate-Viologen Thermochromic Hybrids for Organic Amine Detectors and Memristors with Temperature-Regulating Resistance Switching Characteristics.

There are relatively few reports on the combination of viologen and polyoxometalates (POMs). Herein, we successfully synthesized three viologen-POM-based compounds by in situ transformation of ligands under hydrothermal conditions, namely, {MII(1,4-cby)2[H2(γ-Mo8O26)]}·nH2O (1: M = Ni, n = 4; 2: M = Co, n = 6), and [NiII(1,3-cby)(H2O)4(β-Mo8O26)0.5]·2H2O (3) (1,4-cby·Cl = 1-(4-carboxy-benzyl)-[4,4']bipyridinyl-1-ium, 1,3-cby·Cl = 1-(3-carboxy-benzyl)-[4,4']bipyridinyl-1-ium). Isostructural compounds 1 and 2 exhibit two-dimensional (2D) layer structures with POMs as linking nodes, while compound 3 shows a one-dimensional (1D) metal-organic chain with dissociative POM anions. When the temperature increases, compounds 1-3 show good reversible thermochromism properties and also have a fluorescence quenching effect. Moreover, compounds 1-3 can also be used as detectors for organic amines, especially in the atmosphere of ammonia, ethylenediamine, and diethylamine with an obvious discoloration effect. In addition, compound 1 was used as a material for the preparation of memristors with superior properties (distinct temperature-adjusted resistive switching properties). It shows bipolar resistive switching (RS) behavior at different temperatures of 20, 50, and 100 °C. The results show that the 1-based memristor has good thermal stability, which is important for high-temperature environment applications. It also shows that crystalline viologen-POM-based compounds are ideal candidates for making memristors.

Heterogenous carboxyl-functionalized bilayer ionic liquids/polyoxometalate catalysts for extractant-free oxidative desulfurization

Heterogenous carboxyl-functionalized bilayer ionic liquids/polyoxometalate catalysts were synthesized. The optimized catalyst SiO2(50 nm)-BiIL-PW(Keggin-type) was characterized via FT-IR, XRD, Raman, UV–vis-DRS, XPS, TG, SEM-EDX, TEM, contact angle and N2 adsorption/desorption. Characterization results illuminate that polyoxometalate anions are grafted successfully onto the surface of carrier. The catalyst exhibits good amphiphilicity for both sulphur-containing compounds and hydrogen peroxide. With optimized catalyst, 100% sulfur removal can all be achieved for four model fuels including less active BT using a 4:1 molar ratio of n(H2O2)/n(S) and a low temperature of 40 °C free of extractant, which could be attributed to the better quasi homogeneous microenvironment provided by bilayer ionic liquids. Reaction results demonstrate that polyoxometalate and carrier have significant effects on the catalytic activities. Keggin-type phosphotungstate and 50 nm silica are superior for the desulfurization. ICP-MS analysis and the characterizations of recovered catalyst show no significant leaching of catalytic active component. No decrease was observed in catalytic efficiency after the 8th cycle in scale-up experiments.

Modular co-assembly of peptides and polyoxometalates into underwater adhesives with photoluminescence and adjustable adhesion.

Supramolecular polymerization between cationic peptides and anionic polyoxometalates has emerged as a promising strategy for the creation of peptide-based biomimetic underwater adhesives. However, the extremely rigorous requirements for peptide design are an important obstacle to the fabrication of available peptide adhesives with controlled adhesion and versatile functionality. Inspired by marine sessile organisms in nature, here we reported a modular co-assembly method to easily produce peptide/polyoxometalate underwater adhesive materials through mixing two complementary cationic peptides (Pep1 and Pep2) with a single anionic polyoxometalate K6H[SiW9V3O40] in aqueous solution, which are not possible to be obtained from an individual peptide module. We demonstrated that the relatively hydrophobic Pep1 contributes to the bulk cohesion of the resulting adhesive, while the relatively hydrophilic Pep2 not only enables the interfacial adhesion but also regulates the bulk cohesion of the Pep1/Pep2/SiW9V3 adhesive. Rheological and shear adhesion tests showed that the macroscopic adhesion performance of the resulting adhesive materials could be conveniently adjusted by simply changing the molar ratio of the complementary peptide modules without any complicated peptide design. Interestingly, the luminescence properties of K11[Eu(PW11O39)2] (labelled as EuPW11) could be maintained within the Pep1/Pep2/EuPW11 adhesive even in a water environment. The lifetime of the Pep1/Pep2/EuPW11 adhesive was 2.19 ms. The fluorescence quantum yield of the Pep1/Pep2/EuPW11 adhesive was measured to be 27.46%. This study unveils that the modular co-assembly method can effectively simplify the material design of peptide/polyoxometalate underwater adhesives, which will significantly broaden the horizon of material pools and extend their availability space.

Enhanced adsorption-catalysis combination for the removal of sulphur from fuels using polyoxometalates supported on amphipathic hybrid mesoporous silica nanoparticles.

Polyoxometalate (POM) mesoporous silica-based materials with a low POM loading have been designed with hydrophilic and hydrophobic properties. These materials act as powerful heterogeneous catalysts in oxidative desulfurization (ODS), owing to their ability to adsorb both H2O2 and sulphur-containing compounds from the model oil simultaneously. The formation of charge transfer salts through ion pair interaction with a choline functionality, available on the hybrid silica support, affords robust and recyclable heterogeneous catalysts for the ODS process under mild conditions (45 min and 40 °C). Besides, the nature of the polyoxometalate anions is highly dependent on the characteristics of the silica surface. The masking of silanol groups present on the silica surface using silylating agents, with diverse reactivity and steric hindrance, influences the silica surface-heteropolyanion interactions, as well as heteropolyanion-heteropolyanion interactions. In addition, it modifies the hydrophobic properties of the surface, which is a determining factor in the adsorption properties of non-polar dibenzothiophene (DBT) by the catalysts. Adsorption, an anterior step to the oxidation reaction, has been demonstrated to be key to the superior activity of POM-SiMe3-Chol-MSN, where the silanol groups have been capped by trimethylsilyl groups. For the first time, and to better understand POM-surface and POM-POM anion interactions, an extensive characterization of the materials has been performed using 13C, 31P, and 95Mo MAS NMR spectroscopy and solid-state electrochemical techniques, among others.

Soft landing of polyatomic anions onto three-dimensional semiconductive and conductive substrates.

Soft landing of well-characterized polyoxometalate anions, PW12O40 3- (WPOM) and PMo12O40 3- (MoPOM), was carried out to explore the distribution of anions in the semiconducting 10 and 6 μm-long vertically aligned TiO2 nanotubes as well as 300 μm-long conductive vertically aligned carbon nanotubes (VACNTs). The distribution of soft-landed anions on the surfaces and their penetration into the nanotubes were studied using energy dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM). We observe that soft landed anions generate microaggregates on the TiO2 nanotubes and only reside in the top 1.5 μm of the nanotube height. Meanwhile, soft landed anions are uniformly distributed on top of VACNTs and penetrate into the top 40 μm of the sample. We propose that both the aggregation and limited penetration of POM anions into TiO2 nanotubes is attributed to the lower conductivity of this substrate as compared to VACNTs. This study provides first insights into the controlled modification of three dimensional (3D) semiconductive and conductive interfaces using soft landing of mass-selected polyatomic ions, which is of interest to the rational design of 3D interfaces for electronics and energy applications.

Fine-tuning non-covalent interactions between hybrid metal-oxo clusters and proteins.

Interactions between the protein Hen Egg White Lysozyme (HEWL) and three different hybrid Anderson-Evans polyoxometalate clusters - AE-NH2 (δ-[MnMo6O18{(OCH2)3CNH2}2]3-), AE-CH3 (δ-[MnMo6O18{(OCH2)3CCH3}2]3-) and AE-Biot (δ-[MnMo6O18{(OCH2)3CNHCOC9H15N2OS}2]3-) - were studied via tryptophan fluorescence spectroscopy and single crystal X-ray diffraction. Quenching of tryptophan fluorescence was observed in the presence of all three hybrid polyoxometalate clusters (HPOMs), but the extent of quenching and the binding affinity were greatly dependent on the nature of the organic groups attached to the cluster. Control experiments further revealed the synergistic effect of the anionic polyoxometalate core and organic ligands towards enhanced protein interactions. Furthermore, the protein was co-crystallised with each of the three HPOMs, resulting in four different crystal structures, thus allowing for the binding modes of HPOM-protein interactions to be investigated with near-atomic precision. All crystal structures displayed a unique mode of binding of the HPOMs to the protein, with both functionalisation and the pH of the crystallisation conditions influencing the interactions. From the crystal structures, it was determined that HPOM-protein non-covalent complexes formed through a combination of electrostatic attraction between the polyoxometalate cluster and positively charged surface regions of HEWL, and direct and water-mediated hydrogen bonds with both the metal-oxo inorganic core and the functional groups of the ligand, where possible. Hence, functionalisation of metal-oxo clusters shows great potential in tuning their interactions with proteins, which is of interest for several biomedical applications.

Two 2D Polyoxometalate‐Based Metal‐Organic Complexes Constructed from a New Flexible N‐Donor Ligand with High Capacitance Performances and Low Detection Limits of Cr(VI)

AbstractBy designing and using a new flexible bis(pyrimidine)‐bis(amide) ligand H2L [H2L=N,N′‐bis(4‐pyrimidinecarboxamido)‐1,3‐propane], two new polyoxometalate (POM)‐based metal‐organic complexes (MOCs), H3[Cu2(L)2(PMo12O40)] (1) and [Cu2(H2L)2(β‐Mo8O26)] (2), were synthesized under solvothermal and hydrothermal conditions, respectively. In complexes 1 and 2, metal‐organic units and POM anions are linked together to form two distinct 2D structures. The [PMo12O40]3− (PMo12) anions were used as μ4‐bridging ligands in complex 1 and linked the 1D [Cu(L)]n metal‐organic chains to form a 2D layered structure. The [β‐Mo8O26]4− (Mo8) anions adopted two diverse coordination modes in complex 2 and connected the 1D [Cu(H2L)]n2n+ metal‐organic chains to generate a 2D grid structure. Complexes 1–2 can serve as electrode materials of supercapacitor and show large specific capacitances, up to 1065 and 956 F g−1 at current density of 2 A g−1, respectively, which surpass the parent POM and most of the previous reported POM‐based electrode materials, thus demonstrating the important role of introducing metal‐organic units in improving capacitive performances. Besides, the electrocatalytic redox activities of complexes 1–2 were also studied, both of them can be used as electrochemical sensors to detect Cr(VI) ions. They possess high sensitivity of 0.537 and 0.455 μA μM−1 and low detection limits of 0.16 and 0.33 μM, which are below the maximum content of Cr(VI) in groundwater required by the WHO.

Insights into the Structure of Keggin-Type Polyoxometalate-Based Organic-Inorganic Hybrid Materials: The Actual Ratio of Organic Cations to Heteropolyanions.

Polyoxometalate (POM)-based organic-inorganic hybrid materials possess versatile properties and applications; however, the ratios of organic cations to POM anions still remain to be solved. In this work, 14 POM-based organic-inorganic hybrid materials were synthesized by the precipitation, hydrothermal, and solvent-evaporation methods. These hybrid materials consisted of a wide range of quaternary ammonium and imidazolium cations with different alkyl chains and different Keggin-type heteropolyanions [i.e., phosphotungstic ([PW12O40]3-), phosphomolybdic ([PMo12O40]3-), silicotungstic ([SiW12O40]4-), and silicomolybdic ([SiMo12O40]4-) anions]. Their compositions and structures were characterized complementarily by elemental analysis, powder X-ray diffraction, single-crystal X-ray diffraction, and Fourier transform infrared spectroscopy. The actual ratios of organic cations to heteropolyanions of [PW12O40]3-, [PMo12O40]3-, [SiW12O40]4-, and [SiMo12O40]4- were found to always be 3:1, 3:1, 4:1, and 4:1, respectively, independent of the organic cations, synthesis methods, and reaction parameters. This finding demonstrates that the organic cations completely substituted the protons of the heteropolyacid precursors in the hybrid materials, which thus hardly possessed Brønsted acidity probed by the pyridine adsorption and cellulose hydrolysis reaction. Such complete substitution of the protons arose apparently from the strong noncovalent interactions between the organic cations and heteropolyanions (such as electrostatic and C-H···O interactions) in the POM-based hybrid materials.

Ionic γ-FeO(OH) Nanocrystal Stabilized by Small Isopolymolybdate Clusters as Reactive Core for Water Oxidation.

At near neutral to basic pH, hydrolysis-induced aggregation to insoluble bulk iron-oxide is often regarded as the pitfalls of molecular iron clusters. Iron-oxide nanocrystals are encouragingly active over the molecular clusters and/or bulk oxides albeit, stabilizing such nanostructures in aqueous pH and under turnover condition remain a perdurable challenge. Herein, an Anderson-type [Mo7 O24 ]6- isopolyanion, a small (dimension ca. 0.85 nm) isolable polyoxometalate (POM) possessing only {31} atoms, has been introduced for the first time as a covalent linker to stabilize an infinitely stable and aqueous-soluble γ-FeO(OH) nanocore. During the hydrothermal isolation of the material, a partial dissociation of the parent [Mo7 O24 ]6- may lead to the in situ generation of few analogous [Mox Oy ]n- clusters, proved by Raman study, which can also participate in stabilizing the γ-FeO(OH) nanocore, Mox Oy @FeO(OH). However, due to high ionic charge on {Mo=O} terminals of the [Mox Oy ]n- , they are covalently linked via MoVI -μ2 O-FeIII bridging to γ-FeO(OH) core in Mox Oy @FeO(OH), established by numerous spectroscopic and microscopic evidence. Such bonding mode is more likely as precedent from the coordination motif documented in the transition metal clusters stabilized by this POM. The γ-FeO(OH) nanocore of Mox Oy @FeO(OH) behaves as potent active center for electrochemical water oxidation with a overpotential, 263 mV @ 10 mA cm-2 , lower than that observed for bare γ-FeO(OH). Despite of some molybdenum dissolution from the POM ligands to the electrolyte, residual anionic POM fragments covalently bound to the OER active γ-FeO(OH) core of the Mox Oy @FeO(OH) makes the surface predominantly ionic that results in an ordered electrical double layer to promote a better charge transport across the electrode-electrolyte junction, less likely in bulk γ-FeO(OH).

A Lacunary Polyoxometalate Anion Tightly Sealed in a ZIF‐8 Polyhedron with Ultrafast Cationic Dye Adsorption

AbstractFinding efficient materials for treatment of dye wastewater is a hot research topic in the field of environmental science. In this paper, the mono‐lacunary polyoxometalate anion (SiW11) is completely sealed in a zeolitic imidazolate (ZIF‐8) polyhedron, forming a new polyhedral absorbent, SiW11@ZIF‐8, with an intact surface and a negative charge center. Unlike saturated Keggin type polyoxoanions, SiW11is only stable under neutral conditions and does not release any protons in solutions. Therefore, SiW11@ZIF‐8 does not display the usually observed acid‐induced etching and shows effective and ultrafast adsorption for the cationic dye methylene blue. This work not only indicates that the neutral polyoxoanion is a more suitable candidate to be sealed in ZIF‐8 to form a stable unpunched composite, but also provides a new concept for the design of stable polyoxometalate@ZIF adsorbents to be potentially used in the treatment of cationic dyes in wastewater.

Decavanadate-Type Polyoxometalate Anions Encapsulated in a MIL-100 Framework with Enhanced Mixed Ion–Electron Conduction and Potential Application as Cathode Materials for a Lithium Ion Battery

Decavanadate-Type Polyoxometalate Anions Encapsulated in a MIL-100 Framework with Enhanced Mixed Ion–Electron Conduction and Potential Application as Cathode Materials for a Lithium Ion Battery

Regulating Spin-State Switching by Integrating Polyoxometalate Anion into Spin Crossover System.

Polyoxometalate (POM) anions were successfully integrated into Fe(II) spin crossover (SCO) system, which demonstrates an effective role in regulating spin-state switching properties. Specifically, three drastically different magnetic behaviors of Fe(II) ion in the identical cation [Fe(bpp)2]2+ were achieved by leveraging [Mo6O19]2-, [Mo8O26]4-, and [Na(Mo8O26)]3-, respectively.

An Organo‐Palladium Host Built from a Dynamic Macrocyclic Ligand: Adaptive Self‐Assembly, Induced‐Fit Guest Binding, and Catalysis

AbstractArtificial hosts with rich conformational dynamics are attractive to supramolecular chemists due to their adaptive guest‐binding properties and enzyme‐like catalytic functions. We report here the adaptive self‐assembly and host‐guest catalysis of a new water‐soluble organo‐palladium host (Pd2L2) built from a pyridinium‐bonded macrocyclic ligand (L) andcis‐blocked palladium corners (Pd). While the direct self‐assembly of L with Pd gives rise to a dynamic mixture of products, both neutral polyaromatic hydrocarbons and an anionic polyoxometalate cluster (W10O324−) can template the dominant formation of the Pd2L2host. Guest‐adaptive conformational changes and induced‐fit cavity deformation of the Pd2L2host have been clearly observed in the crystal structures. Moreover, the installation of the electron‐rich W10O324−cluster within the cationic redox‐active host (W10O32⊂Pd2L2) facilitates the efficient and selective C−H photooxidation of toluene derivatives to aldehyde products under mild conditions, thus representing an ideal platform for green supramolecular catalysis.

An Organo-Palladium Host Built from a Dynamic Macrocyclic Ligand: Adaptive Self-Assembly, Induced-Fit Guest Binding, and Catalysis.

Artificial hosts with rich conformational dynamics are attractive to supramolecular chemists due to their adaptive guest-binding properties and enzyme-like catalytic functions. We report here the adaptive self-assembly and host-guest catalysis of a new water-soluble organo-palladium host (Pd2 L2 ) built from a pyridinium-bonded macrocyclic ligand (L) and cis-blocked palladium corners (Pd). While the direct self-assembly of L with Pd gives rise to a dynamic mixture of products, both neutral polyaromatic hydrocarbons and an anionic polyoxometalate cluster (W10 O32 4- ) can template the dominant formation of the Pd2 L2 host. Guest-adaptive conformational changes and induced-fit cavity deformation of the Pd2 L2 host have been clearly observed in the crystal structures. Moreover, the installation of the electron-rich W10 O32 4- cluster within the cationic redox-active host (W10 O32 ⊂Pd2 L2 ) facilitates the efficient and selective C-H photooxidation of toluene derivatives to aldehyde products under mild conditions, thus representing an ideal platform for green supramolecular catalysis.