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), pp. 1169-1185. [Article]
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.
| Item Type: | Article |
|---|---|
| Erschienen: | 2012 |
| Creators: | Amadeu, N. D. ; Grünberg, B. ; Frydel, J. ; Werner, M. ; Limbach, H. H. ; Breitzke, H. ; Buntkowsky, G. |
| Title: | Melting of Low Molecular Weight Compounds in Confinement Observed by H-2-Solid State NMR: Biphenyl, a Case Study |
| Language: | English |
| 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. |
| Journal or Publication Title: | Zeitschrift Fur Physikalische Chemie-International Journal of Research in Physical Chemistry & Chemical Physics |
| Volume of the journal: | 226 |
| Issue Number: | 11-12 |
| Uncontrolled Keywords: | 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 |
| Divisions: | 07 Department of Chemistry > Physical Chemistry 07 Department of Chemistry |
| Date Deposited: | 27 Oct 2014 20:34 |
| Additional Information: | Sp. Iss. SI 067TE Times Cited:1 Cited References Count:88 |
| PPN: | |
| Export: | |
| Suche nach Titel in: | TUfind oder in Google |
 |
Send an inquiry |
Options (only for editors)
 |
Show editorial Details |
Drucken
Impressum