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

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Date
2017
Author
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.
Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 1-5, Zürich, Switzerland
Facultad de Facultad de Ciencias Básicas, Universidad de Medellín, Carrera 87 N 30-65, Medellín, Colombia
Faculty of Physics, Vilnius University, Sauletekio 9, Vilnius, Lithuania
Institut für Anorganische und Analytische Chemie, TU Braunschweig, Hagenring 30, Braunschweig, Germany
Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
Centre de RMN À Tres Hauts Champs, Institut de Sciences Analytiques, Université de Lyon (CNRS/ENS Lyon/UCB Lyon 1), Villeurbanne, France
Laboratoire de Chimie de l'Ens Lyon, Université de Lyon (CNRS/ENS Lyon/UCB LyonUMR 5182), 46 alleé d'Italie, Lyon, France
TY - GEN T1 - Local Structures and Heterogeneity of Silica-Supported M(III) Sites Evidenced by EPR, IR, NMR, and Luminescence Spectroscopies AU - Delley M.F. AU - Lapadula G. AU - Núñez-Zarur F. AU - Comas-Vives A. AU - Kalendra V. AU - Jeschke G. AU - Baabe D. AU - Walter M.D. AU - Rossini A.J. AU - Lesage A. AU - Emsley L. AU - Maury O. AU - Copéret C. Y1 - 2017 UR - http://hdl.handle.net/11407/4261 PB - American Chemical Society AB - ER - @misc{11407_4261, author = {Delley M.F. and Lapadula G. and Núñez-Zarur F. and Comas-Vives A. and Kalendra V. and Jeschke G. and Baabe D. and Walter M.D. and Rossini A.J. and Lesage A. and Emsley L. and Maury O. and Copéret C.}, title = {Local Structures and Heterogeneity of Silica-Supported M(III) Sites Evidenced by EPR, IR, NMR, and Luminescence Spectroscopies}, year = {2017}, abstract = {}, url = {http://hdl.handle.net/11407/4261} }RT Generic T1 Local Structures and Heterogeneity of Silica-Supported M(III) Sites Evidenced by EPR, IR, NMR, and Luminescence Spectroscopies A1 Delley M.F. A1 Lapadula G. A1 Núñez-Zarur F. A1 Comas-Vives A. A1 Kalendra V. A1 Jeschke G. A1 Baabe D. A1 Walter M.D. A1 Rossini A.J. A1 Lesage A. A1 Emsley L. A1 Maury O. A1 Copéret C. YR 2017 LK http://hdl.handle.net/11407/4261 PB American Chemical Society AB OL Spanish (121)
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Abstract
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)3 vs siloxides (M(OSi(OtBu)3)3·L with L = (THF)2 or HOSi(OtBu)3 for 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-enhanced 89Y 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. © 2017 American Chemical Society.
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http://hdl.handle.net/11407/4261
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