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Melting of Low Molecular Weight Compounds in Confinement Observed by H-2-Solid State NMR: Biphenyl, a Case Study

Amadeu, N. D. ; Grünberg, B. ; Frydel, J. ; Werner, M. ; Limbach, H. H. ; Breitzke, H. ; Buntkowsky, G. (2012)
Melting of Low Molecular Weight Compounds in Confinement Observed by H-2-Solid State NMR: Biphenyl, a Case Study.
In: Zeitschrift Fur Physikalische Chemie-International Journal of Research in Physical Chemistry & Chemical Physics, 226 (11-12)
Artikel, Bibliographie

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Kurzbeschreibung (Abstract)

The H-2-NMR solid echo spectra of biphenyl molecules as guests in the mesopores of neat and silylated SBA-15 have been measured as a function of temperature. At low temperatures typical H-2-Pake patterns with parameters of (Q(zz) = 132 kHz, corresponding to Q(cc) = 176 kHz) and (eta = 0.04) are observed. All samples exhibit a strong reduction of the melting point from the bulk value of 342.4 K to values between 222 K and 229 K, depending on both the pore diameter and the surface state and a glass like behavior of the biphenyl molecules in the melting regime. Employing the Roessler two-phase model of the modeling of glass-transitions by H-2-solid state NMR the distribution of activation energies for the rotational motions has been determined. At temperatures closely below the glass-transition temperature deviations from a static Pake pattern of an aromatic deuteron are observed, which indicate a pre-melting motion of biphenyl, which could be caused by C-2-ring flips of the phenyl rings.

Typ des Eintrags: Artikel
Erschienen: 2012
Autor(en): Amadeu, N. D. ; Grünberg, B. ; Frydel, J. ; Werner, M. ; Limbach, H. H. ; Breitzke, H. ; Buntkowsky, G.
Art des Eintrags: Bibliographie
Titel: Melting of Low Molecular Weight Compounds in Confinement Observed by H-2-Solid State NMR: Biphenyl, a Case Study
Sprache: Englisch
Publikationsjahr: 2012
Titel der Zeitschrift, Zeitung oder Schriftenreihe: Zeitschrift Fur Physikalische Chemie-International Journal of Research in Physical Chemistry & Chemical Physics
Jahrgang/Volume einer Zeitschrift: 226
(Heft-)Nummer: 11-12
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Kurzbeschreibung (Abstract):

The H-2-NMR solid echo spectra of biphenyl molecules as guests in the mesopores of neat and silylated SBA-15 have been measured as a function of temperature. At low temperatures typical H-2-Pake patterns with parameters of (Q(zz) = 132 kHz, corresponding to Q(cc) = 176 kHz) and (eta = 0.04) are observed. All samples exhibit a strong reduction of the melting point from the bulk value of 342.4 K to values between 222 K and 229 K, depending on both the pore diameter and the surface state and a glass like behavior of the biphenyl molecules in the melting regime. Employing the Roessler two-phase model of the modeling of glass-transitions by H-2-solid state NMR the distribution of activation energies for the rotational motions has been determined. At temperatures closely below the glass-transition temperature deviations from a static Pake pattern of an aromatic deuteron are observed, which indicate a pre-melting motion of biphenyl, which could be caused by C-2-ring flips of the phenyl rings.

Freie Schlagworte: solid state nmr confinement melting premelting biphenyl mesoporous silica materials nuclear-magnetic-resonance potential applications phase-transitions internal-rotation phenylene motion spin-diffusion drug-delivery glass formers exchange nmr
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Sp. Iss. SI 067TE Times Cited:1 Cited References Count:88

Fachbereich(e)/-gebiet(e): 07 Fachbereich Chemie
07 Fachbereich Chemie > Eduard Zintl-Institut
07 Fachbereich Chemie > Eduard Zintl-Institut > Fachgebiet Physikalische Chemie
Hinterlegungsdatum: 27 Okt 2014 20:34
Letzte Änderung: 03 Jul 2024 02:21
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