Ho(NO_3)_3(C_2H_5O_2N)_4·H_2O的低温热容和热力学函数

Low-Temperature Heat Capacity and Thermodynamic Functions of Ho(NO_3)_3(C_2H_5O_2N)_4·H_2O

合成了稀土(钬,Ho)-氨基酸(甘氨酸,C_2H_5O_2N)二元配合物Ho(NO_3)_3(C_2H_5O_2N)_4·H_2O,并且通过化学分析、元素分析和红外(IR)光谱对配合物进行了表征.用高精度全自动绝热量热仪,测定了该配合物在80-390 K温度区间的定压摩尔热容(C_(p,m)).利用实验测定的热容数据,采用最小二乘法,将热容曲线上热容峰以外的两段平滑区的摩尔热容对折合温度进行拟合,建立了热容随折合温度变化的多项式方程.根据热容与焓、熵的热力学关系,计算出了配合物在80-390 K温度区间内,每隔5 K,相对于298.15 K的摩尔热力学函数(H_(T,m)-H_(298.15,m))和(S_(T,m)-S_(298.15,m)).通过热容曲线分析,计算出了350 K附近转变过程的焓变(△_(trs)H_m)和熵变(△_(trs)S_m).用差示扫描量热法(DSC)测定了配合物的热稳定性.

A complex of a rare-earth metal （Ho） nitrate with glycine （C2H5O2N）, Ho（NO3）3（C2H5O2N）4·H2O, was synthesized, and characterized by chemical analysis, elemental analysis, and infrared （IR） spectroscopy. The thermodynamic properties of the complex were also studied. The low-temperature molar heat capacities at constant pressure （Cp,m） of the complex were measured using a high-precision automatic adiabatic calorimeter over the temperature range from 80 to 390 K. The experimental molar heat capacities at constant pressure were used to deduce the polynomial equations for the heat capacity as a function of reduced temperature by applying the least-squares method to the two smooth stages of the curve. Based on the thermodynamic relationships among heat capacity, entropy, and enthalpy, the thermodynamic functions （HT,m-H298.15,m） and （ST,m-S98.15,m） were derived from the heat capacity data, with temperature intervals of 5 K. The molar enthalpy and entropy changes of the transition process at about 350 K （△trsHm and △trsSm） were calculated from the heat capacity curve. The thermal stability of the complex was determined using differential scanning calorimetry （DSC）.