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

Gedat, E. and Schreiber, A. and Findenegg, G. H. and Shenderovich, I. and Limbach, H. H. and Buntkowsky, G. (2001):
Stray field gradient NMR reveals effects of hydrogen bonding on diffusion coefficients of pyridine in mesoporous silica.
39, In: Magnetic Resonance in Chemistry, pp. S149-S157, [Online-Edition: http://apps.webofknowledge.com/full_record.do?product=WOS&se...],
[Article]

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.

Item Type: Article
Erschienen: 2001
Creators: Gedat, E. and Schreiber, A. and Findenegg, G. H. and Shenderovich, I. and Limbach, H. H. and Buntkowsky, G.
Title: Stray field gradient NMR reveals effects of hydrogen bonding on diffusion coefficients of pyridine in mesoporous silica
Language: English
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.

Journal or Publication Title: Magnetic Resonance in Chemistry
Volume: 39
Uncontrolled Keywords: 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
Divisions: 07 Department of Chemistry
07 Department of Chemistry > Physical Chemistry
Date Deposited: 27 Oct 2014 20:41
Official URL: http://apps.webofknowledge.com/full_record.do?product=WOS&se...
Additional Information:

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

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