Location of protons in anhydrous Keggin heteropolyacids H3PMo12O40 and H3PW12O40 by H-1{P-31}/P-31{H-1} REDOR NMR and DFT quantum chemical calculations - Université de Lille Accéder directement au contenu
Article Dans Une Revue Journal of the American Chemical Society Année : 2002

Location of protons in anhydrous Keggin heteropolyacids H3PMo12O40 and H3PW12O40 by H-1{P-31}/P-31{H-1} REDOR NMR and DFT quantum chemical calculations

M. Fournier
  • Fonction : Auteur
J. F. Paul
  • Fonction : Auteur
L. Delevoye
  • Fonction : Auteur
M. Guelton
  • Fonction : Auteur

Résumé

HeteroPolyAcids (HPA's) are a class of solid acids that have broad applications in many fields of science and technology, including catalysis and chemical engineering. The proton locations within the thermally stable and commonly known Keggin unit, which is the primary structure building unit/block, has remained undetermined in anhydrous HPAs, despite numerous theoretical and experimental efforts. However, Rotational Echo DOuble Resonance (REDOR) NMR and Density Functional Theory (DFT) quantum chemical calculations offer a new opportunity to determine the exact locations of protons within the Keggin unit. The crucial experimental evidence is provided for the basic and very extensively studied acidic form of H8-nXn+M12O40, X = Si, P and M = Mo, W, belonging to the Keggin structure. While showing that the acidic protons are located in the bridging oxygen positions (RP-H = 520 ± 20 pm) in H3PMo12O40 and in the terminal oxygen positions (RP-H = 570 ± 20 pm) in H3PW12O40, REDOR measurements also provide for the first time the structural basis to consistently rank the acid strength for the important class of Keggin solid catalysts.

Domaines

Chimie

Dates et versions

hal-04559180 , version 1 (25-04-2024)

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Citer

S. Ganapathy, M. Fournier, J. F. Paul, L. Delevoye, M. Guelton, et al.. Location of protons in anhydrous Keggin heteropolyacids H3PMo12O40 and H3PW12O40 by H-1{P-31}/P-31{H-1} REDOR NMR and DFT quantum chemical calculations. Journal of the American Chemical Society, 2002, Journal of the American Chemical Society, 124, pp.7821-7828. ⟨10.1021/ja017848n⟩. ⟨hal-04559180⟩
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