Addenda Atoms Research Articles

Impact of the Lithium Cation on the Voltammetry and Spectroscopy of [XVM11O40]n- (X = P, As (n = 4), S (n = 3); M = Mo, W): Influence of Charge and Addenda and Hetero Atoms.

Polyoxometalates (POMs) have been proposed as electromaterials for lithium-based batteries because they provide access to multiple electron transfer reactions coupled to fast lithium ion transport processes and high stability over many redox cycles. Consequently, knowledge of reversible potentials and Li+ cation-POM anion interactions provides a strategic basis for their further development. In this study, detailed cyclic voltammetric studies of a series of [XVVM11O40]n- (XVM11n-) POMs (where X (heteroatom) = P (n = 4), As (n = 4), and S (n = 3) and M (addenda atom) = Mo, W) have been undertaken in CH3CN in the presence of LiClO4, with n-Bu4NPF6 also present when required to keep the ionic strength close to constant value of 0.1 M. An analysis of the data has allowed the impact of the POM charge, and addenda and hetero atoms on the reversible potentials and the interaction between Li+ and the oxidized XVVM11n- and reduced XVIVM11(n+1)- forms of the VV/IV redox couple to be determined. The SVV/IVM113-/4- process is independent of the Li+ concentration, implying the absence of the association of this cation with either SVVM113- or SVIVM114- redox levels. However, lithium-ion association constants for both VV and VIV redox levels were obtained from a comparison of simulated and experimental cyclic voltammograms for the reduction of the more negatively charged XVVM114- (X = P, As; M = Mo, W), since the Li+ interaction with these more negatively charged POMs is much stronger. The interaction between Li+ and the oxidized, XVVM11n-, and reduced, XVIVM11(n+1)-, forms was also investigated by 51V NMR and EPR spectroscopy, respectively, and it was confirmed that, due to their lower charge density, SVVM113- and SVIVM114- interact significantly less strongly with the lithium ion than XVVM114- and XVIVM115- (X = P, As). The lithium-POM association constants are substantially smaller than the corresponding proton association constants reported previously, which is attributed to a smaller surface charge density. The much stronger impact of Li+ on the WVI/V- and MoVI/V-based reductions that occur at more negative potentials than the VV/IV process also has been qualitatively evaluated.

Ln6O8] Cluster-Encapsulating Polyplumbites as New Polyoxometalate Members and Record Inorganic Anion-Exchange Materials for ReO4 - Sequestration.

Various types of polyoxometalates (POMs) have been synthesized since the 19th century, but their assortment has been mostly limited to Groups 5 and 6 metals. Herein, a new family of POMs composed of a carbon group element as the addenda atoms with two distinct phases, LnPbOClO4‐1 (Ln = Sm to Ho, Y) and LnPbOClO4‐2 (Ln = Er and Tm) is reported. Both structures are built from [Ln6O8] rare‐earth metal hexamers being incorporated in [Pb18O32]/[Pb12O24] polyplumbites, and unbound perchlorates as charge‐balancing anions. Impressively, YPbOClO4‐1 and ErPbOClO4‐2 exhibit exceptional uptake capacities (434.7 and 427.7 mg g−1) toward ReO4 −, a chemical surrogate for the key radioactive fission product in the nuclear fuel cycle 99TcO4 −, which are the highest values among all inorganic anion‐exchange materials reported until now. The sorption mechanism is clearly elucidated and visualized by single‐crystal‐to‐single‐crystal structural transformation from ErPbOClO4‐2 to a perrhenate‐containing complex ErPbOReO4, revealing a unique ReO4 − uptake selectivity driven by specific interaction within Pb···O‐ReO3 − bonds.

The role of Dawson Polyoxometalates as interfacial layers on the energy band alignment between indium tin oxide and poly(3-hexylthiophene) films

In this work a series of Dawson Polyoxometalates (POMs) with different cations and addenda atoms were grown as interfacial layers between indium tin oxide (ITO) and regio-regular poly(3-hexylthiophene) (rr-P3HT) in order determine the effect of different POMs films on the energy band alignment at the heterojunction rr-P3HT/ITO. The POMs/ITO and rr-P3HT/POMs/ITO interfaces were investigated by X-ray Photoelectron and Ultra-Violet Photoelectron Spectroscopies (XPS, UPS) to gain insight into their chemical morphology, the energetics of the formed interfaces and the charge carrier barriers. We show that POMs are reduced upon deposition on ITO and the extent of their reduction is controlled by their cation and addenda atom. The deposition of POMs on ITO results to the formation of interface dipoles and the work function of ITO is increased up to 5.9 eV. When, a thin layer of rr-P3HT is formed on top of POMs modified ITO, electron transfer from rr-P3HT to the substrate occurs when the work function of POM/ITO substrates is >4.5 eV, resulting to a pinning of the highest occupied molecular orbital (HOMO) of rr-P3HT and the formation of ohmic contacts. The results were interpreted by the integer charge transfer model (ICT).

Lacunar Keggin Heteropolyacid Salts: Soluble, Solid and Solid-Supported Catalysts

Polyoxometalates are an important class of environmentally friendly catalysts. The Keggin heteropolyacids containing tungsten or molybdenum addenda atoms have received great attention because they have attractive acid and redox properties, which may be easily tunable through changes in their composition and structure. The replacement of their protons by large radium cations makes insoluble the Keggin heteropolyacids and increases their surface area. On the other hand, the removal of tungsten or molybdenum atoms from the Keggin heteropolyanion generates vacancies, which can activate different organic substrates. Therefore, solid lacunar heteropolyacid salts are potentially active catalysts and selective in a plethora of reactions. These catalysts are used either in homo- or heterogeneous conditions. In this review, we wish would highlight recent advances achieved in the chemistry of lacunar Keggin heteropolyacids. We describe their use as solid, soluble or solid-supported catalysts in reactions of oxidation of alcohols and olefins, oxidative desulfurization and acid-catalyzed reactions such as acetalization, esterification, and transesterification.

Cu2+ in Keggin anion – Influence of copper position on electronic structure/redox properties of heteropolyacids. DFT cluster model study

Heteropolyacids systems (HPAs) exhibit a wide range of molecular sizes, compositions and architectures. Modification of those parameters leads to the creation of a structure that presents diverse chemical and catalytic features. In this paper, the theoretical description of electronic structure of tungsten and molybdenum heteropolyacids modified by copper Cu2+ ion (Cu-HPA) has been presented. The obtained results showed that the Cu2+ cation introduced into the Keggin anion, into the position of the central ion or addenda atom(s), influences the acid-base properties of the active centers that are present in the system. In addition, the impact of copper ions on the density of states and character of frontier orbitals has been presented.

Isomer distribution in α-Keggin structures [XW12−nVnO40]−(q+n) X = Si, P (0 ≤ n ≤ 4): A DFT study of free energy and vibrational spectra

Potassium salts of Keggin anions with tungsten and vanadium as addenda atoms ([α-PV n W (12− n ) O 40 ] (3+ n )− 0 ≤ n ≤ 4 and [α-SiV n W (X− n ) O 40 ] (4+ n )− 0 ≤ n ≤ 3) were prepared and analyzed by infrared and Raman spectroscopy. Geometry optimization at a Density Functional Theory (DFT) level was performed and vibrational spectra were obtained for all 54 possible isomers of these anions. The results have been improved by using Polarizable Continuum Model (PCM) to simulate solvent effects. Gibbs free energy values were calculated for all the members of the series. The Boltzmann distribution of the isomers with a given number of vanadium atoms was calculated. The results suggest that (i) the most stable state corresponds to a homogeneous distribution of vanadium between Keggin species and (ii) potential relations between synthetic route and isomer distribution in α-Keggin ions are unjustified on thermodynamic grounds. Calculated Raman spectra are in overall agreement with the experimental data. However, specific bands associated to vanadium substitution are predicted but are not experimentally observed. Les sels de potassium de différents ions de Keggin contenant du tungstène et du vanadium comme additifs ([α-PV n W (12− n ) O 40 ] (3+ n )− 0 ≤ n ≤ 4 et [α-SiV n W (X− n ) O 40 ] (4+ n )− 0 ≤ n ≤ 3) ont été synthétisés et analysés par spectroscopies infrarouge et Raman. La géométrie a été optimisée et les spectres vibrationnels ont été determinés par la méthode DFT pour les 54 isomères possibles de ces ions, l'utilisation de PCM pour simuler les effets de solvant ayant permis d'améliorer les résultats. Les valeurs de l'énergie libre de Gibbs ont été calculées pour chacun des isomères, ainsi que la distribution de Boltzmann pour les isomères associés à un nombre donné d'atomes de vanadium. Les résultats indiquent que l'état le plus stable correspond à la repartition homogène du vanadium entre les ions de Keggin. Une relation éventuelle entre la méthode de synthèse et la distribution des isomères α des ions de Keggin demeure injustifiée sur une base thermodynamique. Les spectres Raman calculés sont globalement en accord avec les données expérimentales. Cependant, certaines bandes sécifiquement dues à la substitution du tungstène par le vanadium sont prévues, mais ne sont pas observées.

ChemInform Abstract: The Anderson‐Evans Polyoxometalate: From Inorganic Building Blocks via Hybrid Organic‐Inorganic Structures to Tomorrows “Bio‐POM”

AbstractReview: 297 refs.

In situ formation of the first proteinogenically functionalized [TeW6O24O2(Glu)]7- structure reveals unprecedented chemical and geometrical features of the Anderson-type cluster.

The chemistry of polyoxometalates (POMs) in a protein environment is an almost unexplored but highly relevant research field as important biological and pharmacological attributes of certain POMs are based on their interactions with proteins. We report on the A-type Anderson-Evans polyoxotungstate, [TeW6O24]6- (TEW), mediated crystallization of Coreopsis grandiflora aurone synthase (cgAUS1) using ∼0.24 mM protein and 1.0 mM TEW. The 1.78 Å crystal structure reveals the covalent binding of TEW to the protein under the formation of an unprecedented polyoxotungstate cluster, [TeW6O24O2(Glu)]7- (GluTEW). The polyoxotungstate-protein complex exhibits the first covalent bond between a protein and the A-type Anderson-Evans cluster, an archetype where up to now no hybrid structures exist. The polyoxotungstate is modified at two of its six addenda tungsten atoms, which covalently bind to the carboxylic oxygen atoms of glutamic acid (Glu157), leading to W-O distances of ∼2.35 Å. This ligand substitution reaction is accompanied by a reduction of the coordination number of two μ3 polyoxotungstate oxygen atoms. This is so far unique since all known hybridizations of the Anderson-Evans POM with organic units have been obtained via the functionalization of the B-type Anderson-Evans structure through its bridging oxygen atoms. The structure reported here proves the reactivity of this POM archetype's addenda atoms as it has been administered into the protein solution as a pre-assembled cluster. Moreover, the novel cluster [TeW6O24O2(Glu)]7- displays the great versatility of the Anderson-Evans POM class.

Tailoring the Synergistic Bronsted-Lewis acidic effects in Heteropolyacid catalysts: Applied in Esterification and Transesterification Reactions.

In order to investigate the influences of Lewis metals on acidic properties and catalytic activities, a series of Keggin heteropolyacid (HPA) catalysts, HnPW11MO39 (M = TiIV, CuII, AlIII, SnIV, FeIII, CrIII, ZrIV and ZnII; for Ti and Zr, the number of oxygen is 40), were prepared and applied in the esterification and transesterification reactions. Only those cations with moderate Lewis acidity had a higher impact. Ti Substituted HPA, H5PW11TiO40, posse lower acid content compared with TixH3−4xPW12O40 (Ti partial exchanged protons in saturated H3PW12O40), which demonstrated that the Lewis metal as an addenda atom (H5PW11TiO40) was less efficient than those as counter cations (TixH3−4xPW12O40). On the other hand, the highest conversion reached 92.2% in transesterification and 97.4% in esterification. Meanwhile, a good result was achieved by H5PW11TiO40 in which the total selectivity of DAG and TGA was 96.7%. In addition, calcination treatment to H5PW11TiO40 make it insoluble in water which resulted in a heterogeneous catalyst feasible for reuse.

Mechanistic Details and Reactivity Descriptors in Oxidation and Acid Catalysis of Methanol

Acid and redox reaction rates of CH3OH-O2 mixtures on polyoxometalate (POM) clusters, together with isotopic, spectroscopic, and theoretical assessments of catalyst properties and reaction pathways, were used to define rigorous descriptors of reactivity and to probe the compositional effects for oxidative dehydrogenation (ODH) and dehydration reactions. 31P-MAS NMR, transmission electron microscopy and titrations of protons with di-tert-butylpyridine during catalysis showed that POM clusters retained their Keggin structure upon dispersion on SiO2 and after use in CH3OH reactions. The effects of CH3OH and O2 pressures and of D-substitution on ODH rates show that C–H activation in molecularly adsorbed CH3OH is the sole kinetically relevant step and leads to reduced centers as intermediates present at low coverages; their concentrations, measured from UV–vis spectra obtained during catalysis, are consistent with the effects of CH3OH/O2 ratios predicted from the elementary steps proposed. First-order ODH rate constants depend strongly on the addenda atoms (Mo vs W) but weakly on the central atom (P vs Si) in POM clusters, because C–H activation steps inject electrons into the lowest unoccupied molecular orbitals (LUMO) of the clusters, which are the d-orbitals at Mo6+ and W6+ centers. H-atom addition energies (HAE) at O-atoms in POM clusters represent the relevant theoretical probe of the LUMO energies and of ODH reactivity. The calculated energies of ODH transition states at each O-atom depend linearly on their HAE values with slopes near unity, as predicted for late transition states in which electron transfer and C–H cleavage are essentially complete. HAE values averaged over all accessible O-atoms in POM clusters provide the appropriate reactivity descriptor for oxides whose known structures allow accurate HAE calculations. CH3OH dehydration proceeds via parallel pathways mediated by late carbenium-ion transition states; effects of composition on dehydration reactivity reflect changes in charge reorganizations and electrostatic forces that stabilize protons at Brønsted acid sites.

The UV and IR Comparative Spectrophotometric Study of Some Saturated and Lacunary Polyoxometalates

Abstract Objectives: The polyoxometalates are a class of inorganic compounds with controllable shapes and sizes, and with excellent properties that make them attractive for various applications. This study is aimed at the comparative UV and IR spectra of Keggin type polyoxometalates. Methods: Compounds under (UV and IR) investigations were divided into several groups to highlight similarities between compounds or classes of compounds for the same category. There are four types of saturated Keggin structures and six lacunar compounds included in this study. The study begins with the UV investigations on aqueous solutions with 10-5 M concentration for these compounds. IR spectra were recorded as KBr pressed pellets. Results: The UV spectras presents large strong peaks between 185-195 nm corresponding to W = Od bonds, between 251-268 nm for W-O-W bridge bonds, depending on heteroatom types (As, Sb). The unsaturated cryptand ligand having Co2+ coordinated presents the most intense peak, due to the involvement of oxygen atoms from terminal W = Od coordinative bonds with high electronic densities in coordination of W-O-Co bond. The IR spectra present many peaks that are associated as follows: for terminal bonds W = Od, 955-970 cm-1; for W-OW bridging bonds, 790-910 cm-1; for W-O-As/Sb bonds to heteroatom, 690-760 cm-1. Vibrations of the bonds between heteroatoms and oxygen (As/Sb-O) appear around 620-660 cm-1. Conclusions: Similarities appear from the recorded spectra, between compounds of the same class, by category association. Very fine displacements of peaks that occur explain the influence of heteroatoms, addenda atoms or coordinated cations.

Effects of Heteroatoms on Electronic States of Divanadium-Substituted γ-Keggin-type Polyoxometalates

Effects of heteroatoms on electronic states of divanadium-substituted γ-Keggin-type polyoxometalates (TBA)4[γ-XV2W10O38(μ-OH)(μ-OR)] (X = Ge, Si; R = Me, Et, n-Pr, H; TBA = tetra(n-butyl)ammonium) and (TBA)4[γ-XV2W10O38(μ-O)] (X = Ge, Si) were investigated, using a combination of nuclear magnetic resonance spectroscopy and density functional theory (DFT) calculations. Both the substitution of SiO4 heteroatom units with larger GeO4 ones and the introduction of more electronegative alkoxo groups in place of hydroxo groups resulted in deshielding of the vanadium nuclei. DFT calculations using the Def2-SVP basis set at TPSSh level of theory could well-reproduce the anionic moieties of a series of divanadium-substituted γ-Keggin-type polyoxometalates, and the estimated chemical shifts approximately reproduced the experimental ones with the individual gauge localized orbital method (SO-IGLO) taking the spin-orbit interaction into account. The magnetic shielding (σ) consists of σd + σp + σSD + σFC, where σd, σp, σSD, and σFC are diamagnetic, paramagnetic, spin-dipolar, and Fermi contact terms, respectively. The σp changed much among (TBA)4[γ-XV2W10O38(μ-OH)2], (TBA)4[γ-XV2W10O38(μ-OH)(μ-OR)], and (TBA)4[γ-XV2W10O38(μ-O)], while σd, σSD, and σFC did not change much. Therefore, the σp largely contributed to the magnetic shielding. Moreover, σp consisted of the occupied-occupied transitions (s-terms) and the occupied-virtual ones (u-terms), and the u-terms were predominant for σp. The most contributing occupied localized orbital consisted of the dz(2) orbital of vanadium, the pz orbital of terminal oxygen related to the V═O bond, and the pz orbital of oxygen of the XO4 unit, whereas the two virtual localized orbitals consisted of the dyz orbital of vanadium and the py orbital of terminal oxygen. Analysis of the structural and electronic characteristics of a series of divanadium-substituted γ-Keggin-type POMs revealed a linear correlation between both (51)V{H} chemical shifts and the reciprocal values of the energy gaps between the corresponding XO4-predominant orbital HOMOs-X and the LUMOs+X (X = 0, 1, or 2). All these results indicate that neighboring XO4 units weakly interact with the addenda atoms and control the electronic states of polyoxometalates and the magnetic shielding of their addenda atoms.

Lacunary Keggin-type heteropolyanion, α-[PMo2W9O39]7−, as an efficient homogenous catalyst for oxidation of aromatic amines

The oxidation of aromatic amines was carried out in the presence of lacunary Keggin-type heteropolyanion with mixed tungsten and molybdenum addenda atoms. In the presence of this heteropolyanion, the nitro compounds were obtained in excellent yields under mild reaction conditions.

Supported dodecaphosphotungstate and undecaphosphotungstate: a study on the kinetic behavior for the oxidation of styrene

Abstract Zirconia supported dodecaphosphotungstate and undecaphosphotungstate were successfully used as heterogeneous catalysts for the liquid-phase solvent-free oxidation of styrene. A detailed kinetic study was carried out in order to study the effect of removal of one addenda atom from the parent Keggin unit. The supported catalysts were also systematically characterized by various physicochemical techniques to show that the Keggin unit remains intact even after supporting on the support. Thermal studies also indicate that the supported catalysts are stable up to 450 °C. Maximum conversion with a single selective product was obtained after 30 h for the undecaphosphotungstate and after 20 h for dodecaphosphotungstate. The rate constants as well as the activation energy for the reaction were determined. From the values of activation energy derived from the Arrhenius plot, different thermodynamic parameters such as enthalpy and Gibbs free energy were also calculated. From the above studies, supported dode...

One-step synthesis of a Keggin-type manganese(II)-substituted phosphotungstate: structural and spectroscopic characterization and non-solvent liquid phase oxidation of styrene

The Keggin-type Cs salt of a mono Mn(II)-substituted phosphotungstate (Cs5[PMnW11O39]) was synthesized from H3PW12O40, MnCl2 and CsCl. The complex was characterized in solution as well as in the solid state by spectroscopic, magnetic and electrochemical techniques. The complex crystallized in tetragonal phase. X-ray structural analysis shows two types of disorder in which the Mn and W atoms are distributed over the 12 positions, and the Mn atom could not be distinguished from the 11 W atoms distributed equally over the 12 addenda atoms in the Keggin structure. The catalytic activity of the complex was evaluated for non-aqueous oxidation of styrene using molecular oxygen. The complex gave >99.0% selectivity towards benzaldehyde and could be reused.

Reactivity of Heteropolytungstate and Heteropolymolybdate Metal Transition Salts in the Synthesis of Dimethyl Carbonate from Methanol and CO2

A series of Keggin-type heteropoly compounds (HPC) having different countercations (Co, Fe) and different addenda atoms (W, Mo) were synthesized and characterized by means of Fourier-Transform Infrared Spectrometer (FT-IR) and X-ray powder diffraction (XRD). The catalytic properties of the prepared catalysts for the dimethyl carbonate (DMC) synthesis from CO2 and CH3OH were investigated. The experimental results showed that the catalytic activity is significantly influenced by the type of the countercation and addenda atoms transition metal. Among the catalysts examined, Co1.5PW12O40 is the most active for the DMC synthesis, owing to the synergetic effect between Co and W. Investigating the effect of the support showed that the least acidic one (Al2O3) enhanced the conversion but decreased the DMC selectivity in favor of that of methyl formate (MF), while that of dimethoxy methane remained stable.

Vanadium(IV)-substituted tungstoantimonate [Sb2W20(VO)2(H2O)4O70]10− : synthesis, crystal structure and electrochemistry

A vanadium(IV)-substituted tungstoantimonate, K8Na2[Sb2W20(VO)2(H2O)4O70]·18.5H2O (1), has been synthesized in aqueous solution and characterized by IR, UV–Vis, elemental analysis, TG and X-ray single-crystal diffraction analysis. The structure of 1 was composed of two V(IV) ions linked to a [Sb2W20O70]14− fragment via V–O(W) bonds; the anions are connected by K+ to construct a two-dimensional network complex. The electrochemical behavior of 1 was investigated in buffer solution (pH 2.5) by cyclic voltammetry. In the potential range between −0.7 and 0.9 V, the compound exhibits successive redox processes of the addenda atoms (W) in a negative potential range, and also redox originating from the substituted atom (V) at a more positive potential. Compound 1 has good electrocatalytic activity towards the reduction of iodate.

Strategies for oxidation catalyzed by polyoxometalates at the interface of homogeneous and heterogeneous catalysis

A basic premise behind the use of polyoxometalates in oxidation chemistry is the fact that polyoxometalates are oxidatively stable. This, a priori, leads to the conclusion that for practical purposes polyoxometalates would have distinct advantages over widely investigated organometallic compounds that are vulnerable to decomposition due to oxidation of the ligand bound to the metal center. Since polyoxometalate synthesis is normally carried out in water by mixing the stoichiometrically required amounts of monomeric metal salts and adjusting the pH to a specific acidic value many structure types are accessible by variation of the reaction stoichiometry, replacement of one or more addenda atoms with other transition or main group metals, and pH control. The structural variety available has enabled the use of polyoxometalates as catalysts for oxidation of hydrocarbons and functionalized organic substrates (alcohols, amines, sulfides, etc.) with a wide range of oxygen donors ranging from molecular oxygen, hydrogen peroxide, nitrous oxide, ozone, alkyl hydroperoxides, periodate, sulfoxide and others. The wide purview of oxidation reactions is enabled because the structural variety leads to oxidation through a number of different mechanistic motifs. From a synthetic organic point of view, the most applicable uses of polyoxometalates as catalysts involve the “green” oxygen donors – hydrogen peroxide and molecular oxygen. Since practical applications are in hand in this area, practical considerations concerned with catalyst recycle and/or recovery and the elimination of environmentally problematic solvents are also coming to the forefront. In this paper, we will present some of our activities in the area of “catalyst engineering” for catalytic synthetic applications by polyoxometalates including: (a) catalytic mesoporous solids from organic-polyoxometalate hybrid materials, (b) fluorous phase polyoxometalates with and without fluorous solvents and (c) the use of aqueous biphasic media for oxidation with hydrogen peroxide.

The State of the Art on Wells‐Dawson Heteropoly‐Compounds. A Review of Their Properties and Applications

AbstractFor Abstract see ChemInform Abstract in Full Text.

The state of the art on Wells–Dawson heteropoly-compounds: A review of their properties and applications

The scientific literature concerning the structure, hydrolytic stability in solution, thermal stability in the solid state, redox-acid properties and applications of heteropoly-compounds (HPCs) with Wells–Dawson structure is summarized in the present work.Wells–Dawson heteropoly-anions possess the formula [(Xn+)2M18O62](16−2n)− where Xn+ represents a central atom (phosphorous(V), arsenic(V), sulfur(VI), fluorine) surrounded by a cage of M addenda atoms, such as tungsten(VI), molybdenum(VI) or a mixture of elements, each of them composing MO6 (M-oxygen) octahedral units. The addenda atoms are partially substituted by other elements, such as vanadium, transition metals, lanthanides, halogens and inorganic radicals. The Wells–Dawson heteropoly-anion is associated with inorganic (H+, alkaline elements, etc.) or organic countercations forming hybrid compounds.Wells–Dawson acids (phospho-tungstic H6P2W18O62·24H2O, phospho-molybdic H6P2Mo18O62·nH2O and arsenic-molybdic H6As2Mo18O62·nH2O) possess super-acidity and a remarkably stability both in solution and in the solid state. These properties make them suitable catalytic materials in homogeneous and heterogeneous liquid-phase reactions replacing the conventional liquid acids (HF, HCl, H2SO4, etc.). Although, the application of the acids in heterogeneous gas-phase reactions is less developed, there is a patented method to oxidize alkanes to carboxylic acids on a supported Wells–Dawson catalyst that combines acid and redox properties.Wells–Dawson anions possess the ability to accept or release electrons through an external potential or upon exposure to visible and UV radiation (electro and photochemical reactions).Additionally, Wells–Dawson HPCs catalyze the oxidation of organic molecules with molecular oxygen, hydrogen peroxide and iodosylarenes; epoxidation and hydrogenation in homogeneous and heterogeneous liquid-phase conditions.The ability of transition metal substituted Wells–Dawson HPCs to be reduced and re-oxidized without degradation of the structure is promising in the application of those HPCs replacing metalloporphyrins catalysts in redox and electrochemical reactions.