Phase transitions and reorientational motions in [Al(OS(CHb>3b>)b>2b>)b>6b>](NOb>3b>)b>3b> and its deuterated analog

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• 作者：Natalia Gó ; rska^a ; ^{gorska@chem.sci.osaka-u.ac.jp} ; Akira Inaba^a ; El偶bieta Szostak^b ; Edward Mikuli^b
• 关键词：Aluminum complex ; DMSO ligand ; Phase transition ; Orientationally disordered crystal ; Adiabatic calorimetry ; IR and Raman spectroscopy
• 刊名：Thermochimica Acta
• 出版年：2012
• 期刊代码：110_00406031
• 类别：ch
• 出版时间：10 April, 2012
• 卷：533
• 期：Complete
• 页码：66-73
• 文件大小：1273 K

摘要

Two phase transitions were found in solid [Al(OS(CHb>3b>)b>2b>)b>6b>](NOb>3b>)b>3b> at Tb>C1b> = 343.1 K by differential scanning calorimetry and at Tb>C2b> = 34.3 K by adiabatic calorimetry. The transition at Tb>C1b> is accompanied by large thermal hysteresis (ca. 30 K) and a large entropy change (76 J K^鈭? mol^鈭?), suggesting an order-disorder-type transition, whereas that at Tb>C2b> has a considerably smaller entropy change (3.4 J K^鈭? mol^鈭?). The phase behavior of the deuterated compound is essentially the same. IR and Raman spectra reveal a reduction in symmetry below Tb>C1b> and a change in the reorientational dynamics of CHb>3b> groups and NOb>3b>^{鈭?/sup> anions, indicating that the highest temperature phase is orientationally disordered. The transition at Tb>C2b> can be explained by a librational soft-mode theory and all complex cations change their orientation in a cooperative manner.}