Motional heterogeneity in single-site silica-supported species revealed by deuteron NMR
Identifieur interne : 002517 ( Istex/Corpus ); précédent : 002516; suivant : 002518Motional heterogeneity in single-site silica-supported species revealed by deuteron NMR
Auteurs : Julia Gathpresent Address Physical Chemistry Eth Zrich Wolfgang-Pauli-Strasse Ch-8093 Zurich Switzerland ; Gina L. Hoaston ; Robert L. Vold ; Romain Berthoud ; Christophe Copret ; Mary Grellier ; Sylviane Sabo-Etienne ; Anne Lesage ; Lyndon EmsleySource :
- Physical Chemistry Chemical Physics [ 1463-9076 ] ; 2009.
Abstract
The molecular dynamics of [SiDMe2] grafted on two amorphous silica materials, mesoporous SBA and non-porous Aerosil, was investigated by deuteron (2H) solid-state NMR spectroscopy. Quadrupole echo (QE), quadrupole CarrPurcellMeiboomGill (QCPMG) and magic angle spinning (MAS) spectra were recorded as a function of temperature. These were analyzed to determine the rates and trajectories of molecular motion of the surface species. The dynamics were modelled as a composite two frame motion with independent rotations around the two SiO bonds. In the first frame there are fast three-site jumps of the SiDMe2 group described by a single rate (k1) and unequal populations of the tetrahedral sites, such that the ratio D:Me:Me is around 1:4:4. In the second frame, the SiO axis makes small step, nearest-neighbour jumps at a rate k2 along an arc defined by the rim of a cone with a fixed half-angle. Both rates were found to be in the fast motional regime (k1,2 > 1010 s1) throughout the experimentally accessible temperature range, 190350 K. The experimental data are compatible only with models that include a distribution of arc lengths, , in the second frame. The best fit of the simulations to the experimental data yields the distributions of the arc length. The results unequivocally demonstrate that even though the sites all have the same average environment, as reported by the isotropic chemical shifts, the dynamics of the grafted species are microscopically spatially heterogeneous with different molecules on the surface having different ranges of motional trajectories and populations. Furthermore, a clear difference in dynamic behavior is observed between the two silica supports, the motion being more constrained on the mesoporous SBA. This differential mobility is possibly due to differences in surface roughness and to the pore structure of SBA compared with the smoother surface of Aerosil.
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DOI: 10.1039/b907665d
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<front><div type="abstract">The molecular dynamics of [SiDMe2] grafted on two amorphous silica materials, mesoporous SBA and non-porous Aerosil, was investigated by deuteron (2H) solid-state NMR spectroscopy. Quadrupole echo (QE), quadrupole CarrPurcellMeiboomGill (QCPMG) and magic angle spinning (MAS) spectra were recorded as a function of temperature. These were analyzed to determine the rates and trajectories of molecular motion of the surface species. The dynamics were modelled as a composite two frame motion with independent rotations around the two SiO bonds. In the first frame there are fast three-site jumps of the SiDMe2 group described by a single rate (k1) and unequal populations of the tetrahedral sites, such that the ratio D:Me:Me is around 1:4:4. In the second frame, the SiO axis makes small step, nearest-neighbour jumps at a rate k2 along an arc defined by the rim of a cone with a fixed half-angle. Both rates were found to be in the fast motional regime (k1,2 > 1010 s1) throughout the experimentally accessible temperature range, 190350 K. The experimental data are compatible only with models that include a distribution of arc lengths, , in the second frame. The best fit of the simulations to the experimental data yields the distributions of the arc length. The results unequivocally demonstrate that even though the sites all have the same average environment, as reported by the isotropic chemical shifts, the dynamics of the grafted species are microscopically spatially heterogeneous with different molecules on the surface having different ranges of motional trajectories and populations. Furthermore, a clear difference in dynamic behavior is observed between the two silica supports, the motion being more constrained on the mesoporous SBA. This differential mobility is possibly due to differences in surface roughness and to the pore structure of SBA compared with the smoother surface of Aerosil.</div>
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<abstract>The molecular dynamics of [SiDMe2] grafted on two amorphous silica materials, mesoporous SBA and non-porous Aerosil, was investigated by deuteron (2H) solid-state NMR spectroscopy. Quadrupole echo (QE), quadrupole CarrPurcellMeiboomGill (QCPMG) and magic angle spinning (MAS) spectra were recorded as a function of temperature. These were analyzed to determine the rates and trajectories of molecular motion of the surface species. The dynamics were modelled as a composite two frame motion with independent rotations around the two SiO bonds. In the first frame there are fast three-site jumps of the SiDMe2 group described by a single rate (k1) and unequal populations of the tetrahedral sites, such that the ratio D:Me:Me is around 1:4:4. In the second frame, the SiO axis makes small step, nearest-neighbour jumps at a rate k2 along an arc defined by the rim of a cone with a fixed half-angle. Both rates were found to be in the fast motional regime (k1,2 > 1010 s1) throughout the experimentally accessible temperature range, 190350 K. The experimental data are compatible only with models that include a distribution of arc lengths, , in the second frame. The best fit of the simulations to the experimental data yields the distributions of the arc length. The results unequivocally demonstrate that even though the sites all have the same average environment, as reported by the isotropic chemical shifts, the dynamics of the grafted species are microscopically spatially heterogeneous with different molecules on the surface having different ranges of motional trajectories and populations. Furthermore, a clear difference in dynamic behavior is observed between the two silica supports, the motion being more constrained on the mesoporous SBA. This differential mobility is possibly due to differences in surface roughness and to the pore structure of SBA compared with the smoother surface of Aerosil.</abstract>
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<istex:fulltextTEI uri="https://api.istex.fr/document/C6F34D69A4410BC46373C012275268393E4CD792/fulltext/tei"><teiHeader><fileDesc><titleStmt><title level="a">Motional heterogeneity in single-site silica-supported species revealed by deuteron NMR</title>
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<notesStmt><note>Electronic supplementary information (ESI) available: Details of motional models used and parameter distributions. See DOI: 10.1039/b907665d</note>
<note>The dynamics of [SiDMe2] grafted on amorphous silica materials is spatially heterogeneous as investigated by deuteron (2H) solid-state NMR spectroscopy.</note>
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<author xml:id="author-1"><persName><forename type="first">Julia</forename>
<surname>GathPresent address: Physical Chemistry, ETH Zrich, Wolfgang-Pauli-Strasse 10, CH-8093 Zurich, Switzerland</surname>
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<email>Lyndon.Emsley@ens-lyon.fr</email>
<affiliation>Universit de Lyon, CNRS/ENS Lyon/UCB Lyon 1, Centre de RMN Trs Hauts Champs, 5 rue de la Doua, 69100 Villeurbanne, France</affiliation>
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<author xml:id="author-2"><persName><forename type="first">Gina L.</forename>
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<affiliation>Department of Physics, College of William and Mary, VA 23187-8795, P.O. Box 8795, Williamsburg, USA</affiliation>
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<author xml:id="author-3"><persName><forename type="first">Robert L.</forename>
<surname>Vold</surname>
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<affiliation>Department of Applied Science, College of William and Mary, VA 23187-8795, P.O. Box 8795, Williamsburg, USA</affiliation>
</author>
<author xml:id="author-4"><persName><forename type="first">Romain</forename>
<surname>Berthoud</surname>
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<affiliation>Universit de Lyon, Institut de Chimie de Lyon, (CNRSUniversit Lyon 1ESCPE Lyon), C2P2 Equipe LCOMS, ESCPE Lyon, 43 boulevard du 11 Novembre, 69616 Villeurbanne Cedex, France</affiliation>
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<author xml:id="author-5"><persName><forename type="first">Christophe</forename>
<surname>Copret</surname>
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<affiliation>Universit de Lyon, Institut de Chimie de Lyon, (CNRSUniversit Lyon 1ESCPE Lyon), C2P2 Equipe LCOMS, ESCPE Lyon, 43 boulevard du 11 Novembre, 69616 Villeurbanne Cedex, France</affiliation>
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<author xml:id="author-6"><persName><forename type="first">Mary</forename>
<surname>Grellier</surname>
</persName>
<affiliation>Laboratoire de Chimie de Coordination, 205, route de Narbonne, 31077-Toulouse cedex 04, France</affiliation>
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<author xml:id="author-7"><persName><forename type="first">Sylviane</forename>
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<affiliation>Laboratoire de Chimie de Coordination, 205, route de Narbonne, 31077-Toulouse cedex 04, France</affiliation>
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<author xml:id="author-8"><persName><forename type="first">Anne</forename>
<surname>Lesage</surname>
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<affiliation>Universit de Lyon, CNRS/ENS Lyon/UCB Lyon 1, Centre de RMN Trs Hauts Champs, 5 rue de la Doua, 69100 Villeurbanne, France</affiliation>
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<affiliation>Universit de Lyon, CNRS/ENS Lyon/UCB Lyon 1, Centre de RMN Trs Hauts Champs, 5 rue de la Doua, 69100 Villeurbanne, France</affiliation>
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<abstract><p>The molecular dynamics of [SiDMe2] grafted on two amorphous silica materials, mesoporous SBA and non-porous Aerosil, was investigated by deuteron (2H) solid-state NMR spectroscopy. Quadrupole echo (QE), quadrupole CarrPurcellMeiboomGill (QCPMG) and magic angle spinning (MAS) spectra were recorded as a function of temperature. These were analyzed to determine the rates and trajectories of molecular motion of the surface species. The dynamics were modelled as a composite two frame motion with independent rotations around the two SiO bonds. In the first frame there are fast three-site jumps of the SiDMe2 group described by a single rate (k1) and unequal populations of the tetrahedral sites, such that the ratio D:Me:Me is around 1:4:4. In the second frame, the SiO axis makes small step, nearest-neighbour jumps at a rate k2 along an arc defined by the rim of a cone with a fixed half-angle. Both rates were found to be in the fast motional regime (k1,2 > 1010 s1) throughout the experimentally accessible temperature range, 190350 K. The experimental data are compatible only with models that include a distribution of arc lengths, , in the second frame. The best fit of the simulations to the experimental data yields the distributions of the arc length. The results unequivocally demonstrate that even though the sites all have the same average environment, as reported by the isotropic chemical shifts, the dynamics of the grafted species are microscopically spatially heterogeneous with different molecules on the surface having different ranges of motional trajectories and populations. Furthermore, a clear difference in dynamic behavior is observed between the two silica supports, the motion being more constrained on the mesoporous SBA. This differential mobility is possibly due to differences in surface roughness and to the pore structure of SBA compared with the smoother surface of Aerosil.</p>
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<title>Motional heterogeneity in single-site silica-supported species revealed by deuteron NMR<fnoteref></fnoteref>
<footnote id="fn1">Electronic supplementary information (ESI) available: Details of motional models used and parameter distributions. See DOI: <url>10.1039/b907665d</url>
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<nameelt>Université de Lyon</nameelt>
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<addrelt>CNRS/ENS Lyon/UCB Lyon 1</addrelt>
<addrelt>Centre de RMN à Très Hauts Champs</addrelt>
<addrelt>5 rue de la Doua</addrelt>
<city>69100 Villeurbanne</city>
<country>France</country>
</address>
<email>Lyndon.Emsley@ens-lyon.fr</email>
<fax>+33 4 78 89 67 61</fax>
<phone>+33 4 26.23.38.92</phone>
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<nameelt>Department of Physics</nameelt>
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<addrelt>P.O. Box 8795</addrelt>
<city>Williamsburg</city>
<postcode>VA 23187-8795</postcode>
<country>USA</country>
</address>
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<orgname>
<nameelt>Department of Applied Science</nameelt>
<nameelt>College of William and Mary</nameelt>
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<addrelt>P.O. Box 8795</addrelt>
<city>Williamsburg</city>
<postcode>VA 23187-8795</postcode>
<country>USA</country>
</address>
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<org>
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<nameelt>Université de Lyon</nameelt>
<nameelt>Institut de Chimie de Lyon</nameelt>
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<nameelt>C2P2 Equipe LCOMS</nameelt>
<nameelt>ESCPE Lyon</nameelt>
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<addrelt>43 boulevard du 11 Novembre</addrelt>
<city>69616 Villeurbanne Cedex</city>
<country>France</country>
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<org>
<orgname>
<nameelt>Laboratoire de Chimie de Coordination</nameelt>
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<addrelt>205</addrelt>
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<city>31077-Toulouse cedex 04</city>
<country>France</country>
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<ictext>The dynamics of [–SiDMe<inf>2</inf>
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<abstract>
<p>The molecular dynamics of [–SiDMe<inf>2</inf>
] grafted on two amorphous silica materials, mesoporous SBA and non-porous Aerosil, was investigated by deuteron (<sup>2</sup>
H) solid-state NMR spectroscopy. Quadrupole echo (QE), quadrupole Carr–Purcell–Meiboom–Gill (QCPMG) and magic angle spinning (MAS) spectra were recorded as a function of temperature. These were analyzed to determine the rates and trajectories of molecular motion of the surface species. The dynamics were modelled as a composite two frame motion with independent rotations around the two Si–O bonds. In the first frame there are fast three-site jumps of the –SiDMe<inf>2</inf>
group described by a single rate (<it>k</it>
<inf>1</inf>
) and unequal populations of the tetrahedral sites, such that the ratio D : Me : Me is around 1 : 4 : 4. In the second frame, the Si–O axis makes small step, nearest-neighbour jumps at a rate <it>k</it>
<inf>2</inf>
along an arc defined by the rim of a cone with a fixed half-angle. Both rates were found to be in the fast motional regime (<it>k</it>
<inf>1,2</inf>
> 10<sup>10</sup>
s<sup>−1</sup>
) throughout the experimentally accessible temperature range, 190–350 K. The experimental data are compatible only with models that include a distribution of arc lengths, <it>λ</it>
, in the second frame. The best fit of the simulations to the experimental data yields the distributions of the arc length. The results unequivocally demonstrate that even though the sites all have the same average environment, as reported by the isotropic chemical shifts, <it>the dynamics of the grafted species are microscopically spatially heterogeneous</it>
with different molecules on the surface having different ranges of motional trajectories and populations. Furthermore, a clear difference in dynamic behavior is observed between the two silica supports, the motion being more constrained on the mesoporous SBA. This differential mobility is possibly due to differences in surface roughness and to the pore structure of SBA compared with the smoother surface of Aerosil.</p>
</abstract>
</art-front>
<art-back>
<ack>
<p>All spectra reported here were acquired at the Rhône-Alpes Large Scale Facility for High Field NMR Spectroscopy (<url>www.ralf-nmr.fr</url>
). We are grateful to David Gajan for providing samples of SBA-15. G.L.H. is grateful to Université Claude Bernard-Lyon I for a visiting professorship.</p>
</ack>
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<mods version="3.6"><titleInfo><title>Motional heterogeneity in single-site silica-supported species revealed by deuteron NMR</title>
</titleInfo>
<titleInfo type="alternative" contentType="CDATA"><title>Motional heterogeneity in single-site silica-supported species revealed by deuteron NMR</title>
</titleInfo>
<name type="personal"><namePart type="given">Julia</namePart>
<namePart type="family">GathPresent address: Physical Chemistry, ETH Zrich, Wolfgang-Pauli-Strasse 10, CH-8093 Zurich, Switzerland</namePart>
<affiliation>Universit de Lyon, CNRS/ENS Lyon/UCB Lyon 1, Centre de RMN Trs Hauts Champs, 5 rue de la Doua, 69100 Villeurbanne, France</affiliation>
<affiliation>E-mail: Lyndon.Emsley@ens-lyon.fr</affiliation>
</name>
<name type="personal"><namePart type="given">Gina L.</namePart>
<namePart type="family">Hoaston</namePart>
<affiliation>Department of Physics, College of William and Mary, VA 23187-8795, P.O. Box 8795, Williamsburg, USA</affiliation>
</name>
<name type="personal"><namePart type="given">Robert L.</namePart>
<namePart type="family">Vold</namePart>
<affiliation>Department of Applied Science, College of William and Mary, VA 23187-8795, P.O. Box 8795, Williamsburg, USA</affiliation>
</name>
<name type="personal"><namePart type="given">Romain</namePart>
<namePart type="family">Berthoud</namePart>
<affiliation>Universit de Lyon, Institut de Chimie de Lyon, (CNRSUniversit Lyon 1ESCPE Lyon), C2P2 Equipe LCOMS, ESCPE Lyon, 43 boulevard du 11 Novembre, 69616 Villeurbanne Cedex, France</affiliation>
</name>
<name type="personal"><namePart type="given">Christophe</namePart>
<namePart type="family">Copret</namePart>
<affiliation>Universit de Lyon, Institut de Chimie de Lyon, (CNRSUniversit Lyon 1ESCPE Lyon), C2P2 Equipe LCOMS, ESCPE Lyon, 43 boulevard du 11 Novembre, 69616 Villeurbanne Cedex, France</affiliation>
</name>
<name type="personal"><namePart type="given">Mary</namePart>
<namePart type="family">Grellier</namePart>
<affiliation>Laboratoire de Chimie de Coordination, 205, route de Narbonne, 31077-Toulouse cedex 04, France</affiliation>
</name>
<name type="personal"><namePart type="given">Sylviane</namePart>
<namePart type="family">Sabo-Etienne</namePart>
<affiliation>Laboratoire de Chimie de Coordination, 205, route de Narbonne, 31077-Toulouse cedex 04, France</affiliation>
</name>
<name type="personal"><namePart type="given">Anne</namePart>
<namePart type="family">Lesage</namePart>
<affiliation>Universit de Lyon, CNRS/ENS Lyon/UCB Lyon 1, Centre de RMN Trs Hauts Champs, 5 rue de la Doua, 69100 Villeurbanne, France</affiliation>
<affiliation>E-mail: Lyndon.Emsley@ens-lyon.fr</affiliation>
</name>
<name type="personal"><namePart type="given">Lyndon</namePart>
<namePart type="family">Emsley</namePart>
<affiliation>Universit de Lyon, CNRS/ENS Lyon/UCB Lyon 1, Centre de RMN Trs Hauts Champs, 5 rue de la Doua, 69100 Villeurbanne, France</affiliation>
<affiliation>E-mail: Lyndon.Emsley@ens-lyon.fr</affiliation>
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<originInfo><publisher>The Royal Society of Chemistry.</publisher>
<dateIssued encoding="w3cdtf">2009</dateIssued>
<copyrightDate encoding="w3cdtf">2009</copyrightDate>
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<abstract>The molecular dynamics of [SiDMe2] grafted on two amorphous silica materials, mesoporous SBA and non-porous Aerosil, was investigated by deuteron (2H) solid-state NMR spectroscopy. Quadrupole echo (QE), quadrupole CarrPurcellMeiboomGill (QCPMG) and magic angle spinning (MAS) spectra were recorded as a function of temperature. These were analyzed to determine the rates and trajectories of molecular motion of the surface species. The dynamics were modelled as a composite two frame motion with independent rotations around the two SiO bonds. In the first frame there are fast three-site jumps of the SiDMe2 group described by a single rate (k1) and unequal populations of the tetrahedral sites, such that the ratio D:Me:Me is around 1:4:4. In the second frame, the SiO axis makes small step, nearest-neighbour jumps at a rate k2 along an arc defined by the rim of a cone with a fixed half-angle. Both rates were found to be in the fast motional regime (k1,2 > 1010 s1) throughout the experimentally accessible temperature range, 190350 K. The experimental data are compatible only with models that include a distribution of arc lengths, , in the second frame. The best fit of the simulations to the experimental data yields the distributions of the arc length. The results unequivocally demonstrate that even though the sites all have the same average environment, as reported by the isotropic chemical shifts, the dynamics of the grafted species are microscopically spatially heterogeneous with different molecules on the surface having different ranges of motional trajectories and populations. Furthermore, a clear difference in dynamic behavior is observed between the two silica supports, the motion being more constrained on the mesoporous SBA. This differential mobility is possibly due to differences in surface roughness and to the pore structure of SBA compared with the smoother surface of Aerosil.</abstract>
<note type="footnote" displayLabel="fn1">Electronic supplementary information (ESI) available: Details of motional models used and parameter distributions. See DOI: 10.1039/b907665d</note>
<note>The dynamics of [SiDMe2] grafted on amorphous silica materials is spatially heterogeneous as investigated by deuteron (2H) solid-state NMR spectroscopy.</note>
<relatedItem type="host"><titleInfo><title>Physical Chemistry Chemical Physics</title>
</titleInfo>
<titleInfo type="abbreviated"><title>Phys. Chem. Chem. Phys.</title>
</titleInfo>
<genre type="journal">journal</genre>
<originInfo><publisher>The Royal Society of Chemistry.</publisher>
</originInfo>
<identifier type="ISSN">1463-9076</identifier>
<identifier type="eISSN">1463-9084</identifier>
<identifier type="coden">PPCPFQ</identifier>
<identifier type="RSC sercode">CP</identifier>
<part><date>2009</date>
<detail type="volume"><caption>vol.</caption>
<number></number>
</detail>
<detail type="issue"><caption>no.</caption>
<number>32</number>
</detail>
<extent unit="pages"><start>6962</start>
<end>6971</end>
<total>10</total>
</extent>
</part>
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<identifier type="istex">C6F34D69A4410BC46373C012275268393E4CD792</identifier>
<identifier type="DOI">10.1039/b907665d</identifier>
<identifier type="ms-id">b907665d</identifier>
<accessCondition type="use and reproduction" contentType="copyright">This journal is © the Owner Societies</accessCondition>
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