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Updated: Jun 21, 2026
11:44
Spin Saturation Transfer Difference NMR (SSTD NMR): A New Tool to Obtain Kinetic Parameters of Chemical Exchange Processes
Published on: November 12, 2016
Isotope-exchange dynamics in isostructural decametalates with profound differences in reactivity
Eric M Villa1, C André Ohlin, James R Rustad
1Department of Chemistry, University of California, Davis, California 95616, USA.
Journal of the American Chemical Society
|August 8, 2009
Summary
Small structural changes in polyoxometalates significantly alter oxygen-isotope exchange rates. These findings impact simulations of reactions at mineral-water interfaces, highlighting the need for accurate structural modeling.
Area of Science:
- Inorganic Chemistry
- Materials Science
- Computational Chemistry
Background:
- Polyoxometalates (POMs) are versatile inorganic clusters with tunable properties.
- Understanding reaction mechanisms in POMs is crucial for catalysis and materials design.
- Isostructural polyoxometalates offer a platform to study structure-property relationships.
Purpose of the Study:
- To investigate the effect of single-site substitution on oxygen-isotope exchange rates in isostructural polyoxometalates.
- To elucidate the pH dependencies of reaction rates within these structures.
- To assess the implications for computational simulations of extended structures.
Main Methods:
- Synthesis of two isostructural polyoxometalates: [H(x)Nb(10)O(28)]((6-x)-) and [H(x)Ti(2)Nb(8)O(28)]((8-x)-).
- Oxygen-isotope exchange experiments to measure reaction rates at various structural sites.
- Analysis of pH dependencies to understand reaction mechanisms.
Main Results:
- A single Ti(IV) for Nb(V) substitution inverted pH dependencies for oxygen-isotope exchange rates.
- All oxygen sites within a structure exhibited similar pH dependencies, reacting over a 10^4 range.
- Reaction pathways involve concerted lattice motions, demonstrating profound sensitivity to structural changes.
Conclusions:
- Polyoxometalate reaction pathways are highly variable, even within the same structural class.
- Accurate, structurally faithful ab initio simulations are essential for understanding reactions involving extended structures.
- Reactions likely proceed through metastable intermediates, necessitating careful consideration in computational modeling.
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