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Multiscale Sampling of a Heterogeneous Water/Metal Catalyst Interface using Density Functional Theory and Force-Field Molecular Dynamics
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Reversible Interfacial Hydride Transfer as a Complementary Tool To Measure Molecular Hydricity
Hye Won Chung1, Hai-Xu Wang1, Sai Puneet Desai2
1Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
Journal of the American Chemical Society
|September 29, 2025
Summary
A new potentiometric method quantifies hydride transfer (ΔGH-) for challenging main group reagents. This HRR potentiometry approach offers insights into reaction environments and reagent behavior, expanding hydricity measurement capabilities.
Area of Science:
- Chemistry
- Electrochemistry
- Physical Chemistry
Background:
- Hydride transfer is crucial in chemical processes, but quantifying thermodynamic hydricity (ΔGH-) is challenging for main group reagents.
- Existing methods for measuring hydricity are limited, especially for reagents resistant to conventional techniques.
Purpose of the Study:
- To develop and validate a novel potentiometric method, HRR potentiometry, for quantifying the thermodynamic hydricity of main group reagents.
- To investigate the influence of reaction environments, such as solvents and water content, on the hydricity of various hydride donors.
- To explore the impact of Lewis acid-base adduct formation and countercations on the effective hydricity of borohydrides.
Main Methods:
- Exploitation of H2 activation and reversible hydride transfer from a metal surface to a molecular reagent (net hydrogen reduction reaction, HRR).
- Development of a potentiometric technique (HRR potentiometry) to measure equilibrium potentials related to hydride transfer.
- Validation of the method using a benzimidazole-based hydride donor and application to formate and borohydride systems.
Main Results:
- HRR potentiometry successfully quantified ΔGH- for main group reagents recalcitrant to other methods.
- Solvent effects on the hydricity of a benzimidazole-based donor were primarily attributed to differential H- solvation.
- Formate hydricity showed strong dependence on water content, while borohydride effective hydricity was influenced by adduct formation but not countercations.
Conclusions:
- HRR potentiometry is a powerful complementary tool for measuring molecular hydricity, offering advantages for challenging substrates.
- The study elucidates the environmental factors affecting hydride transfer reactions and provides a reliable method for their quantification.
- This work expands the toolkit for studying fundamental chemical reactions relevant to catalysis and energy storage.
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