Polyoxometalates are complex molecular cages made of metal and oxygen atoms and are an important tool in experiments. However, they often behave differently than expected in solutions. Chemists at the University of Vienna have now systematically tested their properties and developed an 'atlas' for experiments. In doing so, they are providing a valuable tool for scientists who want to make chemistry, materials research and biomedical applications more reproducible and efficient. The study has been published in Science Advances.
They look like tiny, perfectly ordered mandalas – complex molecular cages made of metal and oxygen atoms. Chemists produce these so-called polyoxometalates (POMs) as versatile model systems for catalysis, energy storage and biomedical applications. But their apparent symmetry can be deceptive. A new study by the University of Vienna, led by Ingrid Gregorovic, Nadiia I. Gumerova and Annette Rompel, shows when such structures remain intact and when they rearrange themselves unnoticed in liquids. With the new data and practical guidelines from their new study, the researchers provide an important basis for future experiments.
When perfect order becomes unstable
Polyoxometalates often behave differently than expected in solution. The new study shows that under many common laboratory conditions, they either decompose or rearrange themselves. Measurements could then unknowingly examine decomposition products instead of the intended molecules – a key reason why results in catalysis, energy research and biomedicine can be difficult to reproduce. Chemists at the University of Vienna want to counteract this problem with their new findings.
About the study
The study focuses on so-called Keplerates – iconic molecular cages similar to a football pattern, consisting of dozens of metal and oxygen atoms and measuring only a few nanometres in size. They serve as model building blocks for reactions and materials. The team systematically tested their stability across pH values, temperatures and common buffer systems. The result is clear: in strongly acidic solutions, the cages remain intact, while at near-neutral pH values, they quickly reorganise into smaller units. Tungsten-based Keplerates prove to be more resistant than their molybdenum counterparts – a practical tip for experiments where neutral media are unavoidable.
A roadmap for reliable chemistry
The new publication expands on the so-called 'Speciation Atlas' (Science Advances, 2023), which provided an initial roadmap for ten widely used POM systems. With their new study, Gregorovic, Gumerova and Rompel now offer a user-friendly extension to this atlas: open data sets, simple stability tests and clear recommendations on which conditions to use – and which to avoid.
'Our goal was to provide guidance for everyday use,' says Annette Rompel. 'Knowing when POM cages are stable – and when they are not – saves time and resources and leads to more reliable results. The expanded atlas not only tells you whether something is stable, but also helps you design experiments and turn ideas into solid results faster.'
Making research more reproducible
By openly sharing their data and offering concrete recommendations, the authors provide a valuable tool for scientists who want to make chemistry, materials research and biomedical applications more reproducible and efficient.
Summary:
- Polyoxometalates are complex molecular cages made of metal and oxygen atoms and are an important tool in experiments. However, they often behave differently than expected in solutions.
- Scientists at the University of Vienna have produced an 'atlas' for future experiments, recommending exactly which conditions to use for reliable experiments and which to avoid.
- With the new data and clear recommendations, they provide a valuable tool for scientists who want to make chemistry, materials research and biomedical applications more reproducible and efficient.
About the University of Vienna
For over 650 years the University of Vienna has stood for education, research and innovation. Today, it is ranked among the top 100 and thus the top four per cent of all universities worldwide and is globally connected.
With degree programmes covering over 180 disciplines, and more than 10,000 employees we are one of the largest academic institutions in Europe. Here, people from a broad spectrum of disciplines come together to carry out research at the highest level and develop solutions for current and future challenges. Its students and graduates develop reflected and sustainable solutions to complex challenges using innovative spirit and curiosity.
Original publication:
Ingrid Gregorovic, Nadiia I. Gumerova, Annette Rompel, Speciation atlas of polyoxometalates in aqueous solution (Part II): Molybdenum browns, Science Advances (2025) Vol 11
DOI: 10.1126/sciadv.aea1910
