Issue 21, 2020

Polyoxometalates in solution: speciation under spotlight


Polyoxometalates (POMs) are a large group of anionic polynuclear metal–oxo clusters with discrete and chemically modifiable structures. In most aqueous POM solutions, numerous, and often highly negatively charged, species of different nuclearities are formed. It is rather difficult to determine the dominant POM species or their combination, which is responsible for the specific POM activity, during a particular application. Thus, the identification of all individual speciation profiles is essential for the successful implementation of POMs in solution applications. This review article summarizes species that are present in isopoly- and heteropolyvanadates, -niobates, -molybdates and -tungstates aqueous solutions and covers their stability and transformations. The ion-distribution diagrams over a wide pH range are presented in a comprehensive manner. These diagrams are intended for the targeted use of POMs, and in a clear form shows species that are in equilibrium at the given pH value. Thus, the data accumulated in this review can serve as both a starting point and a complete reference material for determining the composition of POM solutions. Some examples are highlighted where the POM speciation studies led to a detailed understanding of their role in applications. In doing so, we aim to motivate the POM community for more speciation studies and to make the subject more comprehensible, both for synthetic POM chemists and for scientists with different backgrounds interested in applying POMs in biological, medical, electrochemical, supramolecular and nanochemistry fields, or as homogeneous catalysts and other water-soluble materials.

Graphical abstract: Polyoxometalates in solution: speciation under spotlight

Supplementary files

Article information

Article type
Review Article
15 Jun 2020
First published
29 Sep 2020
This article is Open Access
Creative Commons BY license

Chem. Soc. Rev., 2020,49, 7568-7601

Polyoxometalates in solution: speciation under spotlight

N. I. Gumerova and A. Rompel, Chem. Soc. Rev., 2020, 49, 7568 DOI: 10.1039/D0CS00392A

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