Alkyl group as entropy reservoir in an MMX chain complex, Pt2(n-PenCS2)4I.
Alkyl group as entropy reservoir in an MMX chain complex, Pt2(n-PenCS2)4I.
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DOI：
10.1021/jp046187o
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发表时间：
2005-02
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影响因子：
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通讯作者：
Kazuya Saito;Satoaki Ikeuchi;Y. Nakazawa;A. Sato;M. Mitsumi;T. Yamashita;K. Toriumi;M. Sorai
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文献类型：
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作者：
Kazuya Saito;Satoaki Ikeuchi;Y. Nakazawa;A. Sato;M. Mitsumi;T. Yamashita;K. Toriumi;M. Sorai
通过绝热量热法测量具有四个正戊基的卤桥一维双核金属络合物（所谓的 MMX 链）Pt2(n-PenCS2)4I 的热容。从室温冷却后进行测量时，在 207.4 K 处观察到一级相变。测定的转变焓和熵分别为10.19 kJ mol(-1) 和49.1 J K(-1) mol(-1)。在 324 K 加热时观察到单向相变，并且相变熵基本为零。样品一旦加热到324 K以上，就不会在室温下恢复到初始相，并在173 K时发生高阶相变，在220.5 K时发生一级相变。一级相变的焓和熵分别为11.6 kJ mol(-1)和52.4 J K(-1) mol(-1)。从初始室温相到 324 K 高温相相变时的熵增益大小表明，在 Pt2(n-PenCS2)4I 中，烷基链中保留的大量熵在相变时转移到二硫代羧基上，如 Pt2(n-PrCS2)4I 和 Pt2(n-BuCS2)4I 的情况。
Heat capacity of halogen-bridged one-dimensional binuclear metal complex (so-called MMX chain) having four n-pentyl groups, Pt2(n-PenCS2)4I, was measured by adiabatic calorimetry. A first-order phase transition was observed at 207.4 K when measurement was made after cooling from room temperature. The enthalpy and entropy of transition were determined to be 10.19 kJ mol(-1) and 49.1 J K(-1) mol(-1), respectively. A monotropic phase transition was observed at 324 K on heating, and the entropy of transition was essentially null. The sample once heated above 324 K never returned to the initial phase at room temperature and underwent a higher-order phase transition at 173 K and a first-order phase transition at 220.5 K. The enthalpy and entropy of the first-order phase transition were estimated to be 11.6 kJ mol(-1) and 52.4 J K(-1) mol(-1), respectively. The magnitude of the entropy gain at the phase transition from the initial room-temperature phase to the high-temperature phase at 324 K shows that in Pt2(n-PenCS2)4I a large amount of entropy reserved in alkyl chain is transferred to dithiocarboxylato groups upon the phase transition, as in the cases of Pt2(n-PrCS2)4I and Pt2(n-BuCS2)4I.