稀土高氯酸盐-缬氨酸配合物[Sm_2(L-α-Val)_4(H_2O)_8](ClO_4)_6的低温热容和热化学研究

Low-Temperature Heat Capacities and Thermochemistry on the Complex of Samarium Perchlorate with L-α-Valine Acid:[Sm_2(L-α-Val)_4(H_2O)_8](ClO_4)_6

以高氯酸钐和缬氨酸为原料在蒸馏水中合成了一种稀土高氯酸盐-缬氨酸配合物[Sm2（L-α-Val）4（H2O）8]（ClO4）6。利用TG/DTG、化学和元素分析、FTIR等技术表征了配合物的结构,确定其组成为：[Sm2（L-α-Val）4（H2O）8]（ClO4）6。用精密绝热量热仪测量了它在78~371K温区的热容,用最小二乘法将该温区的热容对温度进行拟合,得到了热容随温度变化的多项式方程。用此方程进行数值积分,得到每隔5K的舒平热容值和相对于298.15K的热力学函数值。根据TG/DTG结果,推测了该配合物的热分解机理。另外,依据Hess定律,通过设计合理的热化学循环,利用等温环境溶解-反应热量计分别测量量热反应的反应物和产物在所选溶剂中的溶解焓,从而确定反应的反应焓为：ΔrHΘm=（24.83±0.85）kJ·mol-1。最后,利用反应的反应焓和其它反应物和产物已知的热力学数据计算出配合物的标准摩尔生成焓为：-（8010.01±3.90）kJ·mol-1。

A complex of samrium perchlorate with L-α-Valine acid,[Sm2（L-α-Val）4（H2O）8]（ClO4）6,was synthesized by the reaction of samarium perchlorate and L-α-Valine acid in distilled water.The title complex was characterized by chemical analysis,elemental analysis,FTIR and TG/DTG.Low-temperature heat capacities were measured by a precision automated adiabatic calorimeter over the temperature range from 78 to 371 K.A polynomial equation of heat capacities as a function of the temperature was fitted by the least-squares method.Based on the fitted polynomial,the smoothed heat capacities and thermodynamic functions of the complex relative to the standard reference temperature 298.15 K were calculated with the interval of 5 K.The possible mechanism about thermal decomposition of the complex was deduced on the basis of the TG/DTG analysis.A reasonable thermochemical cycle was designed on the basis of the Hess law,and the standard molar enthalpies of dissolution for the reactants and products of the designed reaction in the selected solvents were measured by an isoperibol solutionreaction calorimeter,respectively.In addition,the enthalpy change of the reaction was determined to be Δr H⊙m=（24.83±0.85） kJ·mol-1 from the data of the above standard molar enthalpies of dissolution.Eventually,the standard molar enthalpy of formation of the complex was derived to be-（8 010.01±3.90） kJ·mol-1 by the combination of the enthalpy change of the reaction with other auxiliary thermodynamic quantities.