Chemistry:Polyoxometalate

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Short description: Polyatomic ion made of ≥3 transition metal oxyanions bound by oxygen in a 3D structure
The phosphotungstate anion, an example of a polyoxometalate

In chemistry, a polyoxometalate (abbreviated POM) is a polyatomic ion, usually an anion, that consists of three or more transition metal oxyanions linked together by shared oxygen atoms to form closed 3-dimensional frameworks. The metal atoms are usually group 6 (Mo, W) or less commonly group 5 (V, Nb, Ta) and group 7 (Tc , Re) transition metals in their high oxidation states. Polyoxometalates are often colorless, orange or red diamagnetic anions. Two broad families are recognized, isopolymetalates, composed of only one kind of metal and oxide, and heteropolymetalates, composed of one metal, oxide, and a main group oxyanion (phosphate, silicate, etc.). Many exceptions to these general statements exist.[1][2]

Formation

The oxides of d0 metals such as V
2O
5, MoO
3, WO
3 dissolve at high pH to give orthometalates, VO3−
4, MoO2−
4, WO2−
4. For Nb
2O
5 and Ta
2O
5, the nature of the dissolved species at high pH is less clear, but these oxides also form polyoxometalates. As the pH is lowered, orthometalates protonate to give oxide–hydroxide compounds such as WO
3(OH)−
 and VO
3(OH)2−. These species condense via the process called olation. The replacement of terminal M=O bonds, which in fact have triple bond character, is compensated by the increase in coordination number. The nonobservation of polyoxochromate cages is rationalized by the small radius of Cr(VI), which may not accommodate octahedral coordination geometry.[1]

Condensation of the MO
3(OH)n-
 species entails loss of water and the formation of M–O–M linkages. The stoichiometry for hexamolybdate is shown:[3]

6 MoO2−
4 + 10 HCl → [Mo
6O
19]2− + 10 Cl−
 + 5 H
2O

An abbreviated condensation sequence illustrated with vanadates is:[1][4]

4 VO3−
4 + 8 H+
 → V
4O4−
12 + 4 H
2O
5 V
4O4−
12 + 12 H+
 → 2 V
10O
26(OH)4−
2 + 4 H
2O

When such acidifications are conducted in the presence of phosphate or silicate, heteropolymetalate result. For example, the phosphotungstate anion [PW
12O
40]3− consists of a framework of twelve octahedral tungsten oxyanions surrounding a central phosphate group.

History

Dr. James F. Keggin, the discoverer of the Keggin Structure.

Ammonium phosphomolybdate, [PMo
12O
40]3− anion, was reported in 1826.[5] The isostructural phosphotungstate anion was characterized by X-ray crystallography 1934. This structure is called the Keggin structure after its discoverer.[6]

The 1970's witnessed the introduction of quaternary ammonium salts of POMs.[3] This innovation enabled systematic study without the complications of hydrolysis and acid/base reactions. The introduction of 17O NMR spectroscopy allowed the structural characterization of POMs in solution.[7]

Ramazzoite, the first example of a mineral with a polyoxometalate cation, was described in 2016 in Mt. Ramazzo Mine, Liguria, Italy.[8]

Structure and bonding

The typical framework building blocks are polyhedral units, with 6-coordinate metal centres. Usually, these units share edges and/or vertices. The coordination number of the oxide ligands varies according to their location in the cage. Surface oxides tend to be terminal or doubly bridging oxo ligands. Interior oxides are typically triply bridging or even octahedral.[1] POMs are sometimes viewed as soluble fragments of metal oxides.[7]

Recurring structural motifs allow POMs to be classified. Iso-polyoxometalates (isopolyanions) feature octahedral metal centers. The heteropolymetalates form distinct structures because the main group center is usually tetrahedral. The Lindqvist and Keggin structures are common motifs for iso- and heteropolyanions, respectively.

Polyoxometalates typically exhibit coordinate metal-oxo bonds of different multiplicity and strength. In a typical POM such as the Keggin structure [PW
12O
40]3−, each addenda center connects to single terminal oxo ligand, four bridging µ2-O ligands and one bridging µ3-O deriving from the central heterogroup.[9] Metal–metal bonds in polyoxometalates are normally absent and owing to this property, F. Albert Cotton opposed to consider polyoxometalates as form of cluster materials.[10] However, metal-metal bonds are not completely absent in polyoxometalates and they are often present among the highly reduced species.[11]

  • Lindqvist hexamolybdate, Mo
    6    O2−
    19

  • Decavanadate, V
    10    O6−
    28

  • Line drawing of disodium decavanadate, V
    10    O6−
    28

  • Paratungstate B, also called dihydrogen paratungstate, H
    2    W
    12    O10−
    42

  • Mo36-polymolybdate, Mo
    36    O
    112    (H
    2    O)8−
    16

Polymolybdates and tungstates

The polymolybdates and polytungstates are derived, formally at least, from the dianionic [MO4]2- precursors. The most common units for polymolybdates and polyoxotungstates are the octahedral {MO6} centers, sometimes slightly distorted. Some polymolybdates contain pentagonal bipyramidal units. These building blocks are found in the molybdenum blues, which are mixed valence compounds.[1]

Polyoxotechnetates and rhenates

The structure of the polyanion [Tc
20O
68]4−.
Re4O15 polyoxorhenate in grey and blue.png

Polyoxotechnetates form only in strongly acidic conditions, such as in HTcO
4 or trifluoromethanesulfonic acid solutions. The first empirically isolated polyoxotechnetate was the red [Tc
20O
68]4−. It contains both Tc(V) and Tc(VII) in ratio 4: 16 and is obtained as the hydronium salt [H
7O
3]
4[Tc
20O
68] · 4H2O by concentrating an HTcO
4 solution.[12] Corresponding ammonium polyoxotechnetate salt was recently isolated from trifluoromethanesulfonic acid and it has very similar structure.[13] The only polyoxorhenate formed in acidic conditions in presence of pyrazolium cation. The first empirically isolated polyoxorhenate was the white [Re
4O
15]2−. It contains Re(VII) in both octahedral and tetrahedral coordination.[14]

Polyoxotantalates, niobates, and vanadates

The polyniobates, polytantalates, and vanadates are derived, formally at least, from highly charged [MO4]3- precursors. For Nb and Ta, most common members are M6O8−19 (M = Nb, Ta), which adopt the Lindqvist structure. These octaanions form in strongly basic conditions from alkali melts of the extended metal oxides (M2O5), or in the case of Nb even from mixtures of niobic acid and alkali metal hydroxides in aqueous solution. The hexatantalate can also be prepared by condensation of peroxotantalate Ta(O2)3−4 in alkaline media.[15] These polyoxometalates display an anomalous aqueous solubility trend of their alkali metal salts inasmuch as their Cs+ and Rb+ salts are more soluble than their Na+ and Li+ salts. The opposite trend is observed in group 6 POMs.[16]

The decametalates with the formula M10O6−28 (M = Nb,[17] Ta[18]) are isostructural with decavanadate. They are formed exclusively by edge-sharing {MO6} octahedra (the structure of decatungstate W10O4−32 comprises edge-sharing and corner-sharing tungstate octahedra).

Heteroatoms

Main page: Chemistry:Heteropolymetalate

Heteroatoms aside from the transition metal are a defining feature of heteropolymetalates. Many different elements can serve as heteroatoms but most common are PO3−4, SiO4−4, and AsO3−4.

Giant structures

Two views of a [Mo154(NO)14On]z- cluster, omittiing water and counter ions. Also shown is the X-ray powder pattern for the salt.

Polyoxomolybdates include the wheel-shaped molybdenum blue anions and spherical keplerates. The cluster [Mo
154O
420(NO)
14(OH)
28(H
2O)
70]20-
 consists of more than 700 atoms and is the size of a small protein. The anion is in the form of a tire (the cavity has a diameter of more than 20 Å) and an extremely large inner and outer surface. The incorporation of lanthanide ions in molybdenum blues is particularly intriguing.[19] Lanthanides can behave like Lewis acids and perform catalytic properties.[20] Lanthanide-containing polyoxometalates show chemoselectivity[21] and are also able to form inorganic–organic adducts, which can be exploited in chiral recognition.[22]

Oxoalkoxometalates

Oxoalkoxometalates are clusters that contain both oxide and alkoxide ligands.[23] Typically they lack terminal oxo ligands. Examples include the dodecatitanate Ti12O16(OPri)16 (where OPri stands for an alkoxy group),[24] the iron oxoalkoxometalates[25] and iron[26] and copper[27] Keggin ions.

Sulfido, imido, and other O-replaced oxometalates

The terminal oxide centers of polyoxometalate framework can in certain cases be replaced with other ligands, such as S2−, Br−, and NR2−.[5][28] Sulfur-substituted POMs are called polyoxothiometalates. Other ligands replacing the oxide ions have also been demonstrated, such as nitrosyl and alkoxy groups.[23][29]

Polyfluoroxometalate are yet another class of O-replaced oxometalates.[30]

Other

Numerous hybrid organic–inorganic materials that contain POM cores,[31][32][33]

Illustrative of the diverse structures of POM is the ion CeMo12O8−42, which has face-shared octahedra with Mo atoms at the vertices of an icosahedron).[34]

Use and aspirational applications

Oxidation catalysts

POMs are employed as commercial catalysts for oxidation of organic compounds.[35][36]

Efforts continue to extend this theme. POM-based aerobic oxidations have been promoted as alternatives to chlorine-based wood pulp bleaching processes,[37] a method of decontaminating water,[38] and a method to catalytically produce formic acid from biomass (OxFA process).[39] Polyoxometalates have been shown to catalyse water splitting.[40]

Molecular electronics

Some POMs exhibit unusual magnetic properties,[41] which has prompted visions of many applications. One example is storage devices called qubits.[42] non-volatile (permanent) storage components, also known as flash memory devices.[43][44]

Drugs

Potential antitumor and antiviral drugs.[45] The Anderson-type polyoxomolybdates and heptamolybdates exhibit activity for suppressing the growth of some tumors. In the case of (NH3Pr)6[Mo7O24], activity appears related to its redox properties.[46][47] The Wells-Dawson structure can efficiently inhibit amyloid β (Aβ) aggregation in a therapeutic strategy for Alzheimer's disease.[48][49] antibacterial[50] and antiviral uses.

See also

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 Greenwood, N. N.; Earnshaw, A. (1997). Chemistry of the Elements (2nd ed.). Oxford: Butterworth-Heinemann. ISBN 978-0-7506-3365-9. 
  2. ↑ Pope, M. T. (1983). Heteropoly and Isopoly Oxometalates. New York: Springer Verlag. 
  3. ↑ 3.0 3.1 Klemperer, W. G. (1990). "Tetrabutylammonium Isopolyoxometalates". Inorganic Syntheses. Inorganic Syntheses. 27. pp. 74–85. doi:10.1002/9780470132586.ch15. ISBN 9780470132586. 
  4. ↑ Gumerova, Nadiia I.; Rompel, Annette (2020). "Polyoxometalates in solution: speciation under spotlight" (in en). Chemical Society Reviews 49 (21): 7568–7601. doi:10.1039/D0CS00392A. ISSN 0306-0012. PMID 32990698. http://xlink.rsc.org/?DOI=D0CS00392A. 
  5. ↑ 5.0 5.1 Gouzerh, P.; Che, M. (2006). "From Scheele and Berzelius to Müller: polyoxometalates (POMs) revisited and the "missing link" between the bottom up and top down approaches". L'Actualité Chimique 298: 9. 
  6. ↑ Keggin, J. F. (1934). "The Structure and Formula of 12-Phosphotungstic Acid". Proc. R. Soc. A 144 (851): 75–100. doi:10.1098/rspa.1934.0035. Bibcode: 1934RSPSA.144...75K. 
  7. ↑ 7.0 7.1 Day, V. W.; Klemperer, W. G. (1985). "Metal Oxide Chemistry in Solution: The Early Transition Metal Polyoxoanions". Science 228 (4699): 533–541. doi:10.1126/science.228.4699.533. PMID 17736064. Bibcode: 1985Sci...228..533D. 
  8. ↑ Kampf, Anthony R.; Rossman, George R.; Ma, Chi; Belmonte, Donato; Biagioni, Cristian; Castellaro, Fabrizio; Chiappino, Luigi (April 4, 2018). "Ramazzoite, [Mg8Cu12(PO4)(CO3)4(OH)24(H2O)20[(H0.33SO4)3(H2O)36], the first mineral with a polyoxometalate cation"]. European Journal of Mineralogy 30 (4): 182–186. doi:10.1127/ejm/2018/0030-2748. Bibcode: 2018EJMin..30..827K. https://pubs.geoscienceworld.org/eurjmin/article/530707/?searchresult=1. Retrieved 21 May 2018. 
  9. ↑ Mingos, D.M.P. (1999). Bonding and Charge Distribution in Polyoxometalates: A Bond Valence Approach. Springer. ISBN 978-3-662-15621-6. 
  10. ↑ Chisholm, M. H.; of Newnham, Lord Lewis of (2008). "Frank Albert Cotton. 9 April 1930—20 February 2007". Biogr. Mem. Fellows R. Soc. 54: 95–115. doi:10.1098/rsbm.2008.0003. 
  11. ↑ Kondinski, Aleksandar (2021). "Metal-MetalBonds, Metal–metal bonds in polyoxometalate chemistry". Nanoscale 13 (32): 13574–13592. doi:10.1039/D1NR02357H. PMID 34477632. https://pubs.rsc.org/en/content/articlelanding/2021/nr/d1nr02357h. 
  12. ↑ German, Konstantin E.; Fedoseev, Alexander M.; Grigoriev, Mikhail S.; Kirakosyan, Gayane A.; Dumas, Thomas; Den Auwer, Christophe; Moisy, Philippe; Lawler, Keith V. et al. (24 September 2021). "A 70‐Year‐Old Mystery in Technetium Chemistry Explained by the New Technetium Polyoxometalate [H7O3]4[Tc20O68]⋅4H2O". Chemistry – A European Journal 27 (54): 13624–13631. doi:10.1002/chem.202102035. PMID 34245056. 
  13. ↑ Zegke, Markus; Grödler, Dennis; Roca Jungfer, Maximilian; Haseloer, Alexander; Kreuter, Meike; Neudörfl, Jörg M.; Sittel, Thomas; James, Christopher M. et al. (2022-01-17). "Ammonium Pertechnetate in Mixtures of Trifluoromethanesulfonic Acid and Trifluoromethanesulfonic Anhydride" (in en). Angewandte Chemie International Edition 61 (3): e202113777. doi:10.1002/anie.202113777. ISSN 1433-7851. PMID 34752692. 
  14. ↑ Volkov, Mikhail A.; Novikov, Anton P.; Borisova, Nataliya E.; Grigoriev, Mikhail S.; German, Konstantin E. (10 August 2023). "Intramolecular Re···O Nonvalent Interactions as a Stabilizer of the Polyoxorhenate(VII)". Inorganic Chemistry. doi:10.1021/acs.inorgchem.3c01863. 
  15. ↑ Fullmer, L. B.; Molina, P. I.; Antonio, M. R.; Nyman, M. (2014). "Contrasting ion-association behaviour of Ta and Nb polyoxometalates". Dalton Trans. 2014 (41): 15295–15299. doi:10.1039/C4DT02394C. PMID 25189708. 
  16. ↑ Anderson, T. M.; Thoma, S. G.; Bonhomme, F.; Rodriguez, M. A.; Park, H.; Parise, J. B.; Alan, T. M.; Larentzos, J. P. et al. (2007). "Lithium Polyniobates. A Lindqvist-Supported Lithium−Water Adamantane Cluster and Conversion of Hexaniobate to a Discrete Keggin Complex". Crystal Growth & Design 7 (4): 719–723. doi:10.1021/cg0606904. 
  17. ↑ Graeber, E. J.; Morosin, B. (1977). "The molecular configuration of the decaniobate ion (Nb17O286−)". Acta Crystallographica B 33 (7): 2137–2143. doi:10.1107/S0567740877007900. 
  18. ↑ Matsumoto, M.; Ozawa, Y.; Yagasaki, A.; Zhe, Y. (2013). "Decatantalate—The Last Member of the Group 5 Decametalate Family". Inorg. Chem. 52 (14): 7825–7827. doi:10.1021/ic400864e. PMID 23795610. 
  19. ↑ Al-Sayed, Emir; Rompel, Annette (2022-03-02). "Lanthanides Singing the Blues: Their Fascinating Role in the Assembly of Gigantic Molybdenum Blue Wheels" (in en). ACS Nanoscience Au 2 (3): 179–197. doi:10.1021/acsnanoscienceau.1c00036. ISSN 2694-2496. PMID 35726275. 
  20. ↑ Barrett, Anthony G. M.; Christopher Braddock, D. (1997). "Scandium(III) or lanthanide(III) triflates as recyclable catalysts for the direct acetylation of alcohols with acetic acid". Chemical Communications (4): 351–352. doi:10.1039/a606484a. http://xlink.rsc.org/?DOI=a606484a. 
  21. ↑ Boglio, Cécile; Lemière, Gilles; Hasenknopf, Bernold; Thorimbert, Serge; Lacôte, Emmanuel; Malacria, Max (2006-05-12). "Lanthanide Complexes of the Monovacant Dawson Polyoxotungstate [α1-P2W17O6110− as Selective and Recoverable Lewis Acid Catalysts"] (in en). Angewandte Chemie International Edition 45 (20): 3324–3327. doi:10.1002/anie.200600364. ISSN 1433-7851. PMID 16619320. https://onlinelibrary.wiley.com/doi/10.1002/anie.200600364. 
  22. ↑ Sadakane, Masahiro; Dickman, Michael H.; Pope, Michael T. (2001-06-01). "Chiral Polyoxotungstates. 1. Stereoselective Interaction of Amino Acids with Enantiomers of [Ce III (α 1 -P 2 W 17 O 61 )(H 2 O) x 7- . The Structure of dl -[Ce 2 (H 2 O) 8 (P 2 W 17 O 61 ) 2 ] 14-"] (in en). Inorganic Chemistry 40 (12): 2715–2719. doi:10.1021/ic0014383. ISSN 0020-1669. PMID 11375685. https://pubs.acs.org/doi/10.1021/ic0014383. 
  23. ↑ 23.0 23.1 Pope, Michael Thor; Müller, Achim (1994). Polyoxometalates: From Platonic Solids to Anti-Retroviral Activity. Springer. ISBN 978-0-7923-2421-8. 
  24. ↑ Day, V. W.; Eberspacher, T. A.; Klemperer, W. G.; Park, C. W. (1993). "Dodecatitanates: a new family of stable polyoxotitanates". J. Am. Chem. Soc. 115 (18): 8469–8470. doi:10.1021/ja00071a075. 
  25. ↑ Bino, Avi; Ardon, Michael; Lee, Dongwhan; Spingler, Bernhard; Lippard, Stephen J. (2002). "Synthesis and Structure of [Fe13O4F24(OMe)12]5−: The First Open-Shell Keggin Ion". J. Am. Chem. Soc. 124 (17): 4578–4579. doi:10.1021/ja025590a. PMID 11971702. 
  26. ↑ Sadeghi, Omid; Zakharov, Lev N.; Nyman, May (2015). "Aqueous formation and manipulation of the iron-oxo Keggin ion". Science 347 (6228): 1359–1362. doi:10.1126/science.aaa4620. PMID 25721507. Bibcode: 2015Sci...347.1359S. 
  27. ↑ Kondinski, A.; Monakhov, K. (2017). "Breaking the Gordian Knot in the Structural Chemistry of Polyoxometalates: Copper(II)–Oxo/Hydroxo Clusters". Chemistry: A European Journal 23 (33): 7841–7852. doi:10.1002/chem.201605876. PMID 28083988. 
  28. ↑ Errington, R. John; Wingad, Richard L.; Clegg, William; Elsegood, Mark R. J. (2000). "Direct Bromination of Keggin Fragments To Give [PW9O28Br6]3−: A Polyoxotungstate with a Hexabrominated Face". Angew. Chem. 39 (21): 3884–3886. doi:10.1002/1521-3773(20001103)39:21<3884::AID-ANIE3884>3.0.CO;2-M. PMID 29711675. 
  29. ↑ Gouzerh, P.; Jeannin, Y.; Proust, A.; Robert, F.; Roh, S.-G. (1993). "Functionalization of polyoxomolybdates: the example of nitrosyl derivatives". Mol. Eng. 3 (1–3): 79–91. doi:10.1007/BF00999625. 
  30. ↑ Schreiber, Roy E.; Avram, Liat; Neumann, Ronny (2018). "Self-Assembly through Noncovalent Preorganization of Reactants: Explaining the Formation of a Polyfluoroxometalate". Chemistry - A European Journal 24 (2): 369–379. doi:10.1002/chem.201704287. PMID 29064591. 
  31. ↑ Song, Y.-F.; Long, D.-L.; Cronin, L. (2007). "Non covalently connected frameworks with nanoscale channels assembled from a tethered polyoxometalate–pyrene hybrid". Angew. Chem. Int. Ed. 46 (21): 3900–3904. doi:10.1002/anie.200604734. PMID 17429852. 
  32. ↑ Guo, Hong-Xu; Liu, Shi-Xiong (2004). "A novel 3D organic–inorganic hybrid based on sandwich-type cadmium heteropolymolybdate: [Cd4(H2O)2(2,2′-bpy)2] Cd[Mo6O12(OH)3(PO4)2(HPO4)2]2 [Mo2O4(2,2′-bpy)2]2·3H2O". Inorganic Chemistry Communications 7 (11): 1217. doi:10.1016/j.inoche.2004.09.010. 
  33. ↑ Blazevic, Amir; Rompel, Annette (January 2016). "The Anderson–Evans polyoxometalate: From inorganic building blocks via hybrid organic–inorganic structures to tomorrows "Bio-POM"" (in en). Coordination Chemistry Reviews 307: 42–64. doi:10.1016/j.ccr.2015.07.001. 
  34. ↑ Dexter, D. D.; Silverton, J. V. (1968). "A New Structural Type for Heteropoly Anions. The Crystal Structure of (NH4)2H6(CeMo12O42)·12H2O". J. Am. Chem. Soc. 1968 (13): 3589–3590. doi:10.1021/ja01015a067. 
  35. ↑ Misono, Makoto (1993). "Catalytic chemistry of solid polyoxometalates and their industrial applications". Mol. Eng. 3 (1–3): 193–203. doi:10.1007/BF00999633. 
  36. ↑ Kozhevnikov, Ivan V. (1998). "Catalysis by Heteropoly Acids and Multicomponent Polyoxometalates in Liquid-Phase Reactions". Chem. Rev. 98 (1): 171–198. doi:10.1021/cr960400y. PMID 11851502. 
  37. ↑ Gaspar, A. R.; Gamelas, J. A. F.; Evtuguin, D. V.; Neto, C. P. (2007). "Alternatives for lignocellulosic pulp delignification using polyoxometalates and oxygen: a review". Green Chem. 9 (7): 717–730. doi:10.1039/b607824a. 
  38. ↑ Hiskia, A.; Troupis, A.; Antonaraki, S.; Gkika, E.; Kormali, P.; Papaconstantinou, E. (2006). "Polyoxometallate photocatalysis for decontaminating the aquatic environment from organic and inorganic pollutants". Int. J. Env. Anal. Chem. 86 (3–4): 233. doi:10.1080/03067310500247520. 
  39. ↑ Wölfel, R.; Taccardi, N.; Bösmann, A.; Wasserscheid, P. (2011). "Selective catalytic conversion of biobased carbohydrates to formic acid using molecular oxygen". Green Chem. 13 (10): 2759. doi:10.1039/C1GC15434F. 
  40. ↑ Rausch, B.; Symes, M. D.; Chisholm, G.; Cronin, L. (2014). "Decoupled catalytic hydrogen evolution from a molecular metal oxide redox mediator in water splitting". Science 345 (6202): 1326–1330. doi:10.1126/science.1257443. PMID 25214625. Bibcode: 2014Sci...345.1326R. 
  41. ↑ Müller, A.; Sessoli, R.; Krickemeyer, E.; Bögge, H; Meyer, J.; Gatteschi, D.; Pardi, L.; Westphal, J. et al. (1997). "Polyoxovanadates: High-Nuclearity Spin Clusters with Interesting Host–Guest Systems and Different Electron Populations. Synthesis, Spin Organization, Magnetochemistry, and Spectroscopic Studies". Inorg. Chem. 36 (23): 5239–5240. doi:10.1021/ic9703641. 
  42. ↑ Lehmann, J.; Gaita-Ariño, A.; Coronado, E.; Loss, D. (2007). "Spin qubits with electrically gated polyoxometalate molecules". Nanotechnology 2 (5): 312–317. doi:10.1038/nnano.2007.110. PMID 18654290. Bibcode: 2007NatNa...2..312L. 
  43. ↑ "Flash memory breaches nanoscales", The Hindu.
  44. ↑ Busche, C.; Vila-Nadal, L.; Yan, J.; Miras, H. N.; Long, D.-L.; Georgiev, V. P.; Asenov, A.; Pedersen, R. H. et al. (2014). "Design and fabrication of memory devices based on nanoscale polyoxometalate clusters". Nature 515 (7528): 545–549. doi:10.1038/nature13951. PMID 25409147. Bibcode: 2014Natur.515..545B. 
  45. ↑ Rhule, Jeffrey T.; Hill, Craig L.; Judd, Deborah A. (1998). "Polyoxometalates in Medicine". Chem. Rev. 98 (1): 327–358. doi:10.1021/cr960396q. PMID 11851509. 
  46. ↑ Hasenknopf, Bernold (2005). "Polyoxometalates: introduction to a class of inorganic compounds and their biomedical applications". Frontiers in Bioscience 10 (1–3): 275–87. doi:10.2741/1527. PMID 15574368. 
  47. ↑ Pope, Michael; Müller, Achim (1994). Polyoxometalates: From Platonic Solids to Anti-Retroviral Activity - Springer. Topics in Molecular Organization and Engineering. 10. pp. 337–342. doi:10.1007/978-94-011-0920-8. ISBN 978-94-010-4397-7. 
  48. ↑ Gao, Nan; Sun, Hanjun; Dong, Kai; Ren, Jinsong; Duan, Taicheng; Xu, Can; Qu, Xiaogang (2014-03-04). "Transition-metal-substituted polyoxometalate derivatives as functional anti-amyloid agents for Alzheimer's disease" (in en). Nature Communications 5: 3422. doi:10.1038/ncomms4422. PMID 24595206. Bibcode: 2014NatCo...5.3422G. 
  49. ↑ Bijelic, Aleksandar; Aureliano, Manuel; Rompel, Annette (2019-03-04). "Polyoxometalates as Potential Next‐Generation Metallodrugs in the Combat Against Cancer" (in en). Angewandte Chemie International Edition 58 (10): 2980–2999. doi:10.1002/anie.201803868. ISSN 1433-7851. PMID 29893459. 
  50. ↑ Bijelic, Aleksandar; Aureliano, Manuel; Rompel, Annette (2018). "The antibacterial activity of polyoxometalates: structures, antibiotic effects and future perspectives" (in en). Chemical Communications 54 (10): 1153–1169. doi:10.1039/C7CC07549A. ISSN 1359-7345. PMID 29355262. 

Further reading

  • Long, D. L.; Burkholder, E.; Cronin, L. (2007). "Polyoxometalate Clusters, Nanostructures and Materials: From Self-Assembly to Designer Materials and Devices". Chem. Soc. Rev. 36 (1): 105–121. doi:10.1039/b502666k. PMID 17173149. 
  • Pope, M. T.; Müller, A. (1991). "Polyoxometalate Chemistry: An Old Field with New Dimensions in Several Disciplines". Angew. Chem. Int. Ed. Engl. 30: 34–48. doi:10.1002/anie.199100341. 
  • Hill, C. L. (1998). "Special Volume on Polyoxometalates". Chem. Rev. 98 (1): 1–2. doi:10.1021/cr960395y. PMID 11851497. 
  • Cronin, L.; Müller, A. (2012). Cronin, L.; Müller, A.. eds. "Special Issue on Polyoxometalates". Chem. Soc. Rev. 2012 (22): 7325–7648. doi:10.1039/C2CS90087D. PMID 23052289. 



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