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| Titel: |
A study of crystal structure and molecular dynamics by XRD and 1H NMR in bis-thiourea N-methylpyridinium iodide |
| Auteur: |
Pajzderska, A. Małuszynska, H. Grottel, M. Gdaniec, M. Wąsicki, J. |
| Verschenen in: |
Molecular physics |
| Paginering: | Jaargang 104 (2006) nr. 12 pagina's 1819-1826 |
| Jaar: |
2006-06-20 |
| Inhoud: |
Crystal and molecular structures of two orthorhombic phases of bis-thiourea N-methylpyridinium iodide [(NH2)2CS]2C5H5N [image omitted]I- were determined by a single-crystal X-ray diffraction method. Both phases were discovered earlier by DSC analysis. At 297 K the complex crystallizes in the space group Cmcm with a = 15.742(3) Å, b = 11.349(2) Å, c = 8.360(2) Å, and at 100 K in the space group Pbcn with the cell parameter c tripled. The first-order reversible phase transition occurs at 155 K on cooling and at 160 K on heating. At room temperature all N-methylpyridinium cations are dynamically disordered, while at 100 K the ratio of ordered to statically disordered cations is 2:1. Thiourea-iodide ribbons are well ordered in both crystal phases. 1H NMR analysis performed for the title complex and its deuterated counterpart has revealed a reorientation of methyl group in the low-temperature phase; and in the high temperature phase, a reorientation of N-methylpyridinium cation over inequivalent barriers followed by a probable flip-reorientation of the thiourea molecules. For steric reasons the latter motion is possible only if preceded by a flip-motion of the NH2 group. Activation energy values for the proposed cation and thiourea motions are given. |
| Uitgever: |
Taylor & Francis |
| Bronbestand: |
Elektronische Wetenschappelijke Tijdschriften |
Details van artikel 1 van 17 gevonden artikelen
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