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Inorganics
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Advances in Polyoxometalates for Supramolecular Architecture, Biomimetics and Bioapplications
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Advances in Polyoxometalates for Supramolecular Architecture, Biomimetics and Bioapplications

A special issue of Inorganics (ISSN 2304-6740). This special issue belongs to the section "Coordination Chemistry".

Deadline for manuscript submissions: closed (30 June 2023) | Viewed by 9592

Special Issue Editor

Dr. Kirill Grzhegorzhevskii

E-Mail Website
Guest Editor
Institute of Natural Sciences and Mathematics, Ural Federal University, 620002 Yekaterinburg, Russia
Interests: polyoxometalates; nanocluster; supramolecular structure; photophysics; click-reactions; self-assembling; hybrid materials
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Polyoxometalate (POM) chemistry spans across coordination compounds and hierarchical supramolecular ensembles. Only five elements (V, Mo, W, Nb and Ta) possess the unique combination of ionic radius and atom shell configuration to produce diversity in polynuclear iso- and hetero-complexes: Evans–Anderson, Keggin, Well–Dawson and even giant POM-like Keplerates, etc. POM exhibit various scenarios when being embedded into hybrid organic structures via coordination and electrostatic interactions, weak van der Waals forces and hydrogen bonding. Along with the possibility to graft the organic linkers, the POM are a powerful platform for the design of supramolecular architectures. Using POM as a nano-scaled template, the supramolecular structure of biomimetic ensembles can be flexibly tuned, providing the desired geometry for electrons and energy transfer or molecular recognition.

In this Special Issue, we wish to cover artificial molecular architectures, such as hybrid structures, coordination complexes with enzyme-like activity or other POM-embedded systems for biological applications.

Dr. Kirill Grzhegorzhevskii
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Inorganics is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • polyoxometalates
  • hybrid materials
  • biomimetics
  • supramolecular
  • bioapplications
  • artificial enzymes

Published Papers (6 papers)

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Research

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12 pages, 4442 KiB  
Article
A Nanoscale Cobalt Functionalized Strandberg-Type Phosphomolybdate with β-Sheet Conformation Modulation Ability in Anti-Amyloid Protein Misfolding
by Man Wang, Jiai Hua, Pei Zheng, Yuanzhi Tian, Shaodan Kang, Junjun Chen, Yifan Duan and Xiang Ma
Inorganics 2023, 11(11), 442; https://doi.org/10.3390/inorganics11110442 - 18 Nov 2023
Viewed by 1414
Abstract
For decades, amyloid β-peptide (Aβ) misfolding aggregates with β-sheet structures have been linked to the occurrence and advancement of Alzheimer’s disease (AD) development and progression. As a result, modulating the misfolding mode of Aβ has been regarded as [...] Read more.
For decades, amyloid β-peptide (Aβ) misfolding aggregates with β-sheet structures have been linked to the occurrence and advancement of Alzheimer’s disease (AD) development and progression. As a result, modulating the misfolding mode of Aβ has been regarded as an important anti-amyloid protein misfolding strategy. A polyoxometalate based on {Co(H2O)4}2+ complex and [P2Mo5O23]6− fragments, K8{[Co(H2O)4][HP2Mo5O23]2}·8H2O (abbreviated as CoPM), has been synthesized and structurally characterized using elemental analysis, single-crystal X-ray diffraction (SXRD), IR, UV spectra, bond valence sums (Σs) calculation, and powder XRD (PXRD). CoPM’s primary component, as revealed by structural analysis, is a nanoscale polyoxoanion made of [Co(H2O)4]2+ sandwiched between two [P2Mo5O23]6− pieces. Notably, it is demonstrated that CoPM efficiently modulates Aβ aggregates’ β-sheet-rich conformation. Full article
(This article belongs to the Special Issue Advances in Polyoxometalates for Supramolecular Architecture, Biomimetics and Bioapplications)
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10 pages, 2860 KiB  
Article
A Series of Lanthanide Complexes with Keggin-Type Monolacunary Phosphotungstate: Synthesis and Structural Characterization
by Vladimir S. Korenev, Taisiya S. Sukhikh and Maxim N. Sokolov
Inorganics 2023, 11(8), 327; https://doi.org/10.3390/inorganics11080327 - 01 Aug 2023
Cited by 1 | Viewed by 886
Abstract
The coordination of rare-earth metal ions (Ln3+) to polyoxometalates (POM) is regarded as a way of modifying and controlling their properties, such as single-molecular magnetism or luminescent behavior. The half-sandwich complexes of Ln3+ with monolacunary Keggin POMs (Ln3+/POM [...] Read more.
The coordination of rare-earth metal ions (Ln3+) to polyoxometalates (POM) is regarded as a way of modifying and controlling their properties, such as single-molecular magnetism or luminescent behavior. The half-sandwich complexes of Ln3+ with monolacunary Keggin POMs (Ln3+/POM = 1:1) are of particular interest, since the Ln3+ retains its ability to coordinate extra ligands. Thus, the knowledge of the exact structures of 1:1 Ln/POM complexes is important for the development of reliable synthetic protocols for hybrid complexes. In this work, we isolated three 1:1 Gd3+/POM complexes of the general formula Cat4Gd(PW11O39)·xH2O (Cat = K+ or Me4N+). Complex (Me4N)2K2[Gd(H2O)2PW11O39]·5H2O (1) is polymeric, revealing a layered structural motif via bridging Gd3+ and K+ ions. Complexes (Me4N)6K2[Gd(H2O)3PW11O39]2·20H2O (2) and (Me4N)7K[Gd(H2O)3PW11O39]2·12H2O (3) are classified as dimeric; the difference between them consists of the different crystal packing of the polyoxometalates, which is induced by a variation in the cationic composition. Isostructural complexes have also been characterized for praseodymium, europium, terbium and dysprosium. The coordination number of Ln3+ (8) persists in all the compounds, while the binding mode of the POM varies, giving rise to different architectures with two or three H2O co-ligands per Ln3+. However, whatever the particular structure and exact composition, the {Ln(PW11O39)} moieties are always involved in bonding with each other with the formation either of polymeric chains or dimeric units. In water, these aggregates can dissociate with the formation of [Ln(H2O)4PW11O39]4-. This behavior must be taken into account when choosing L for the design of hybrid {Ln(L)POM} complexes. Full article
(This article belongs to the Special Issue Advances in Polyoxometalates for Supramolecular Architecture, Biomimetics and Bioapplications)
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15 pages, 3175 KiB  
Article
Covalent Grafting of Eosin Y to the Giant Keplerate {Mo132} through an Organosilicon Linker in Homogeneous Regime
by Andrey Denikaev, Grigory Kim, Evgeny Greshnyakov, Nikolai Moskalenko and Kirill Grzhegorzhevskii
Inorganics 2023, 11(6), 239; https://doi.org/10.3390/inorganics11060239 - 30 May 2023
Cited by 2 | Viewed by 1069
Abstract
The template effect of giant polyoxometalates (POM) shows promising results towards the supramolecular design of hybrid materials suitable for photocatalytic reactions. Here, we demonstrate a novel synthetic approach for covalently grafting the xanthene dye eosin Y (EY) to the nanoscale Keplerate POM {Mo [...] Read more.
The template effect of giant polyoxometalates (POM) shows promising results towards the supramolecular design of hybrid materials suitable for photocatalytic reactions. Here, we demonstrate a novel synthetic approach for covalently grafting the xanthene dye eosin Y (EY) to the nanoscale Keplerate POM {Mo132} via an organosilicon linker (3-aminopropyltrimethoxysilane, APTMS) in a homogeneous regime. Using a phase transfer agent, tetrabutylammonium bromide, we solubilize the Keplerate POM modified with six {Si(CH2)3NH2} groups, {Mo132}@Si6, in a series of organic solvents—acetonitrile, acetone, tetrahydrofuran, and dichloromethane—to perform post-functionalization by using an NHS-ester of EY. Both IR and Raman spectroscopy affirm the preservation of the POM’s structure and showcase an amide bond formation between POM and EY in the obtained conjugate {Mo132}@Si6@EY@TBA. Grafting’s success is observed through significant downfield shifting of EY’s aromatic protons’ signals on the 1H NMR spectrum as compared to the spectra of EY and EY-NHS. The current synthetic approach enables us to exercise precise control of the stoichiometry in the POM-dye conjugates—1:1 for the POM-EY system—as confirmed by elemental analysis. Comprehensive photophysical analysis of {Mo132}@Si6@EY@TBA by means of UV-Vis and steady-state and time-resolved fluorescence measurements points to an existing strong interaction between molecular orbitals of EY and {Mo132}, leading to a photoinduced electron transfer, partial fluorescence quenching, and elongation of the excited state’s lifetime. These findings demonstrate that using APTMS as an organosilicon linker in tandem with the Keplerate POM as a nanoscale template can be readily applied as a routine synthetic procedure for grafting various organic dyes or other organic molecules bearing a carboxylic group in their structure to the giant POM surface in a variety of aprotic organic solvents. Full article
(This article belongs to the Special Issue Advances in Polyoxometalates for Supramolecular Architecture, Biomimetics and Bioapplications)
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19 pages, 4942 KiB  
Article
TiO2-Embedded Biocompatible Hydrogel Production Assisted with Alginate and Polyoxometalate Polyelectrolytes for Photocatalytic Application
by Renat Mansurov, Irina Pavlova, Pavel Shabadrov, Anastasiya Levchenko, Alexey Krinochkin, Dmitry Kopchuk, Igor Nikonov, Anna Prokofyeva, Alexander Safronov and Kirill Grzhegorzhevskii
Inorganics 2023, 11(3), 92; https://doi.org/10.3390/inorganics11030092 - 21 Feb 2023
Cited by 1 | Viewed by 1499
Abstract
The hybrid hydrogel materials meet important social challenges, including the photocatalytic purification of water and bio-medical applications. Here, we demonstrate two scenarios of polyacrylamide-TiO2 (PAAm@TiO2) composite hydrogel design using calcium alginate (Alg-Ca) or Keplerate-type polyoxometalates (POMs) {Mo132} tuning [...] Read more.
The hybrid hydrogel materials meet important social challenges, including the photocatalytic purification of water and bio-medical applications. Here, we demonstrate two scenarios of polyacrylamide-TiO2 (PAAm@TiO2) composite hydrogel design using calcium alginate (Alg-Ca) or Keplerate-type polyoxometalates (POMs) {Mo132} tuning the polymer network structure. Calcium alginate molding allowed us to produce polyacrylamide-based beads with an interpenetrating network filled with TiO2 nanoparticles Alg-Ca@PAAm@TiO2, demonstrating the photocatalytic activity towards the methyl orange dye bleaching. Contrastingly, in the presence of the POM, the biocompatible PAAm@TiO2@Mo132 composite hydrogel was produced through the photo-polymerization approach (under 365 nm UV light) using vitamin B2 as initiator. For both types of the synthesized hydrogels, the thermodynamic compatibility, swelling and photocatalytic behavior were studied. The influence of the hydrogel composition on its structure and the mesh size of its network were evaluated using the Flory–Rehner equation. The proposed synthetic strategies for the composite hydrogel production can be easily scaled up to the industrial manufacturing of the photocatalytic hydrogel beads suitable for the water treatment purposes or the biocompatible hydrogel patch for medical application. Full article
(This article belongs to the Special Issue Advances in Polyoxometalates for Supramolecular Architecture, Biomimetics and Bioapplications)
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13 pages, 3599 KiB  
Article
Supramolecular Host–Guest Assemblies of [M6Cl14]2–, M = Mo, W, Clusters with γ-Cyclodextrin for the Development of CLUSPOMs
by Anton A. Ivanov, Pavel A. Abramov, Mohamed Haouas, Yann Molard, Stéphane Cordier, Clément Falaise, Emmanuel Cadot and Michael A. Shestopalov
Inorganics 2023, 11(2), 77; https://doi.org/10.3390/inorganics11020077 - 07 Feb 2023
Cited by 4 | Viewed by 1784
Abstract
Host–guest assemblies open up opportunities for developing novel functional CLUSPOM multicomponent systems based on transition metal clusters (CLUS), polyoxometalates (POMs) and macrocyclic organic ligands. In water–ethanol solution γ-cyclodextrin (γ-CD) interacts with halide metal clusters [M6Cl14]2– (M = Mo, [...] Read more.
Host–guest assemblies open up opportunities for developing novel functional CLUSPOM multicomponent systems based on transition metal clusters (CLUS), polyoxometalates (POMs) and macrocyclic organic ligands. In water–ethanol solution γ-cyclodextrin (γ-CD) interacts with halide metal clusters [M6Cl14]2– (M = Mo, W) to form sandwich-type structures. The supramolecular association between the clusters and CDs, however, remains weak in solution, and the interactions are not strong enough to prevent the hydrolysis of the inorganic guest. Although analysis of the resulting crystal structures reveals inclusion complexation, 1H NMR experiments in solution show no specific affinity between the two components. The luminescent properties of the host–guest compounds in comparison with the initial cluster complexes are also studied to evaluate the influence of CD. Full article
(This article belongs to the Special Issue Advances in Polyoxometalates for Supramolecular Architecture, Biomimetics and Bioapplications)
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Review

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23 pages, 11478 KiB  
Review
Keggin Heteropolyacid Salt Catalysts in Oxidation Reactions: A Review
by Marcio Jose da Silva, Alana Alves Rodrigues and Neide Paloma Gonçalves Lopes
Inorganics 2023, 11(4), 162; https://doi.org/10.3390/inorganics11040162 - 11 Apr 2023
Viewed by 2250
Abstract
Keggin heteropolyacids (HPAs) are metal–oxygen clusters with strong Bronsted acidity. The conversion of HPAs to metal salts can result in Lewis acidity, improving their performance in oxidation reactions. In this review, the main routes for the synthesis of Keggin-type heteropolyacids salts, as well [...] Read more.
Keggin heteropolyacids (HPAs) are metal–oxygen clusters with strong Bronsted acidity. The conversion of HPAs to metal salts can result in Lewis acidity, improving their performance in oxidation reactions. In this review, the main routes for the synthesis of Keggin-type heteropolyacids salts, as well their use as catalysts in oxidation processes of a plethora of substrates, such as monoterpenes, olefins, aldehydes, terpene alcohols, and aromatics, are described. Green reactants such as hydrogen peroxide and molecular oxygen are used as oxidants. These reactions are of interest to several industries because they can be used to produce drugs, additives, fragrances, and fine chemicals. The high efficiency of Keggin HPA with green oxidants contributes to a reduction in the environmental impact of these processes, as preconize the principles of green chemistry. Moreover, Keggin HPAs can be converted to bifunctional catalysts by the modification of their structure, total or partial replacement of their protons with Lewis acid metal cations, or the introduction of these cations into the Keggin anion structure, replacing the addenda atoms (i.e., W and Mo). Aspects linked to the synthesis and characterization of these catalysts are discussed herein, with emphasis on infrared spectroscopy and powder XRD patterns. The most recent advances achieved in the development of catalytic oxidation systems based on Keggin HPA salts are also addressed. Full article
(This article belongs to the Special Issue Advances in Polyoxometalates for Supramolecular Architecture, Biomimetics and Bioapplications)
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