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Stray field gradient NMR reveals effects of hydrogen bonding on diffusion coefficients of pyridine in mesoporous silica

Gedat, E. ; Schreiber, A. ; Findenegg, G. H. ; Shenderovich, I. ; Limbach, H. H. ; Buntkowsky, G. (2001)
Stray field gradient NMR reveals effects of hydrogen bonding on diffusion coefficients of pyridine in mesoporous silica.
In: Magnetic Resonance in Chemistry, 39
Artikel, Bibliographie

Kurzbeschreibung (Abstract)

The diffusion of pyridine confined in mesoporous silica MCM-41 (d(pore) = 3.3 nm) was studied with stray field gradient (SFG) NMR diffusometry as a function of the filling factor of the mesopores at room temperature, employing a laboratory-built SFG setup. The translational diffusion of pyridine in MCM-41 is found to be anisotropic and the diffusion parallel to the pores' cylinder axes is much faster than that perpendicular to them. The parallel diffusion coefficient depends strongly on the filling level of the guest liquid inside the pores. For a filling level of 25, which corresponds approximately to a monomolecular layer of pyridine molecules hydrogen bonded to surface-SiOH groups, a parallel diffusion coefficient of D-parallel to = 1.0 X 10(-9) m(2) s(-1) is found, which is slower than the diffusion coefficient of the bulk liquid (D = 1.6 X 10(-9) m(2) s(-1)). For higher filling factors the parallel diffusion coefficient increases and at a filling factor of 85 a diffusion coefficient of D-parallel to = 6.8 X 10(-9) m(2) s(-1) is reached. The perpendicular diffusion coefficient of D-perpendicular to = 3.7 +/- 2.0 X 10(-11) m(2) s(-1) is independent of the filling factor. Employing additional N-15 MAS data for the pyridine inside the mesopores, a microscopic model of the diffusion is proposed, which depends on the exchange of the slowly diffusing hydrogen-bonded surface pyridine molecules with fast-diffusing free pyridine molecules inside the pores. Copyright (C) 2001 John Wiley & Sons, Ltd.

Typ des Eintrags: Artikel
Erschienen: 2001
Autor(en): Gedat, E. ; Schreiber, A. ; Findenegg, G. H. ; Shenderovich, I. ; Limbach, H. H. ; Buntkowsky, G.
Art des Eintrags: Bibliographie
Titel: Stray field gradient NMR reveals effects of hydrogen bonding on diffusion coefficients of pyridine in mesoporous silica
Sprache: Englisch
Publikationsjahr: 2001
Titel der Zeitschrift, Zeitung oder Schriftenreihe: Magnetic Resonance in Chemistry
Jahrgang/Volume einer Zeitschrift: 39
URL / URN: http://apps.webofknowledge.com/full_record.do?product=WOS&se...
Kurzbeschreibung (Abstract):

The diffusion of pyridine confined in mesoporous silica MCM-41 (d(pore) = 3.3 nm) was studied with stray field gradient (SFG) NMR diffusometry as a function of the filling factor of the mesopores at room temperature, employing a laboratory-built SFG setup. The translational diffusion of pyridine in MCM-41 is found to be anisotropic and the diffusion parallel to the pores' cylinder axes is much faster than that perpendicular to them. The parallel diffusion coefficient depends strongly on the filling level of the guest liquid inside the pores. For a filling level of 25, which corresponds approximately to a monomolecular layer of pyridine molecules hydrogen bonded to surface-SiOH groups, a parallel diffusion coefficient of D-parallel to = 1.0 X 10(-9) m(2) s(-1) is found, which is slower than the diffusion coefficient of the bulk liquid (D = 1.6 X 10(-9) m(2) s(-1)). For higher filling factors the parallel diffusion coefficient increases and at a filling factor of 85 a diffusion coefficient of D-parallel to = 6.8 X 10(-9) m(2) s(-1) is reached. The perpendicular diffusion coefficient of D-perpendicular to = 3.7 +/- 2.0 X 10(-11) m(2) s(-1) is independent of the filling factor. Employing additional N-15 MAS data for the pyridine inside the mesopores, a microscopic model of the diffusion is proposed, which depends on the exchange of the slowly diffusing hydrogen-bonded surface pyridine molecules with fast-diffusing free pyridine molecules inside the pores. Copyright (C) 2001 John Wiley & Sons, Ltd.

Freie Schlagworte: nmr stray field gradient nmr hydrogen bonding diffusion pyridine mesoporous silica mcm-41 anomalous segment diffusion anisotropic self-diffusion molecular-sieves water-molecules pore structure polymer melts fringe-field rabbit lens h-1-nmr mcm-41
Zusätzliche Informationen:

Sp. Iss. SI 495NK Times Cited:7 Cited References Count:40

Fachbereich(e)/-gebiet(e): 07 Fachbereich Chemie
07 Fachbereich Chemie > Eduard Zintl-Institut > Fachgebiet Physikalische Chemie
Hinterlegungsdatum: 27 Okt 2014 20:41
Letzte Änderung: 28 Mai 2019 12:00
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