Local Structures and Heterogeneity of Silica-Supported M(III) Sites Evidenced by EPR, IR, NMR, and Luminescence Spectroscopies

Murielle F. Delley, Giuseppe Lapadula, Francisco Núñez-Zarur, Aleix Comas-Vives, Vidmantas Kalendra, Gunnar Jeschke, Dirk Baabe, Marc D. Walter, Aaron J. Rossini, Anne Lesage, Lyndon Emsley, Olivier Maury, Christophe Copéret

Resultado de la investigación: Contribución a una revistaArtículo

34 Citas (Scopus)

Resumen

© 2017 American Chemical Society. Grafting molecular precursors on partially dehydroxylated silica followed by a thermal treatment yields silica-supported M(III) sites for a broad range of metals. They display unique properties such as high activity in olefin polymerization and alkane dehydrogenation (M = Cr) or efficient luminescence properties (M = Yb and Eu) essential for bioimaging. Here, we interrogate the local structure of the M(III) surface sites obtained from two molecular precursors, amides M(N(SiMe3)2)3vs siloxides (M(OSi(OtBu)3)3·L with L = (THF)2or HOSi(OtBu)3for M = Cr, Yb, Eu, and Y, by a combination of advanced spectroscopic techniques (EPR, IR, XAS, UV-vis, NMR, luminescence spectroscopies). For paramagnetic Cr(III), EPR (HYSCORE) spectroscopy shows hyperfine coupling to nitrogen only when the amide precursor is used, consistent with the presence of nitrogen neighbors. This changes their specific reactivity compared to Cr(III) sites in oxygen environments obtained from siloxide precursors: no coordination of CO and oligomer formation during the polymerization of ethylene due to the presence of a N-donor ligand. The presence of the N-ligand also affects the photophysical properties of Yb and Eu by decreasing their lifetime, probably due to nonradiative deactivation of excited states by N-H bonds. Both types of precursors lead to a distribution of surface sites according to reactivity for Cr, luminescence spectroscopy for Yb and Eu, and dynamic nuclear polarization surface-enhanced89Y NMR spectroscopy (DNP SENS). In particular, DNP SENS provides molecular-level information about the structure of surface sites by evidencing the presence of tri-, tetra-, and pentacoordinated Y-surface sites. This study provides unprecedented evidence and tools to assess the local structure of metal surface sites in relation to their chemical and physical properties.
Idioma originalInglés estadounidense
Páginas (desde-hasta)8855-8867
Número de páginas13
PublicaciónJournal of the American Chemical Society
Volumen139
N.º26
DOI
EstadoPublicada - 5 jul 2017

Huella Profundice en los temas de investigación de 'Local Structures and Heterogeneity of Silica-Supported M(III) Sites Evidenced by EPR, IR, NMR, and Luminescence Spectroscopies'. En conjunto forman una huella única.

  • Citar esto

    Delley, M. F., Lapadula, G., Núñez-Zarur, F., Comas-Vives, A., Kalendra, V., Jeschke, G., Baabe, D., Walter, M. D., Rossini, A. J., Lesage, A., Emsley, L., Maury, O., & Copéret, C. (2017). Local Structures and Heterogeneity of Silica-Supported M(III) Sites Evidenced by EPR, IR, NMR, and Luminescence Spectroscopies. Journal of the American Chemical Society, 139(26), 8855-8867. https://doi.org/10.1021/jacs.7b02179, https://doi.org/10.1021/jacs.7b02179