2,5-二氯苯甲酸与5,5′-二甲基-2,2′-联吡啶稀土钬配合物的晶体结构、热分解反应动力学及热力学
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摘要
本文通过常规溶剂挥发法,合成了钬的三元配合物:[Ho(2,5-DClBA)_3(5,5′-DM-2,2′-bipy)]2(2,5-DClBA=2,5-二氯苯甲酸根; 5,5′-DM-2,2′-bipy=5,5′-二甲基-2,2′-联吡啶).通过EDTA络合滴定分析、元素分析、红外光谱以及X射线粉末衍射等手段对配合物进行了表征,利用X射线单晶衍射仪测定了钬配合物的单晶结构.晶体结构分析表明,该晶体是一个双核分子,属于三斜晶系, Pī空间群.每个双核分子包含两个Ho(Ⅲ)离子、6个2,5-二氯苯甲酸根配体和两个5,5′-二甲基-2,2′-联吡啶配体.相邻的双核单元通过C–H···Cl氢键以及Cl-π作用组装成一维和二维超分子结构.利用TG-DTG/FTIR技术研究了钬配合物的热分解机理.用非线性等转化率法得到钬配合物第二步分解反应的活化能E随转化率a的变化关系,结果表明该步是一个简单反应,因此,进一步采用改进的双等双步法来确定钬配合物第二步分解反应的机理函数.通过计算得到了钬配合物的动力学参数(活化能E和指前因子A)和热力学参数(ΔH~≠、ΔG~≠和ΔS~≠).利用差示扫描量热(DSC)技术对钬配合物的摩尔热容值进行了测定.将所得的平均摩尔热容值与折合温度利用最小二乘法进行拟合得到了多项式方程.将多项式方程结合热力学方程进行计算得到了配合物的舒平摩尔热容值以及焓变、熵变等热力学函数值.
The ternary lanthanide Ho(Ⅲ) complex, [Ho(2,5-DClBA)_3(5,5′-DM-2,2′-bipy)]2(2,5-DClBA=2,5-dichlorobenzoate; 5,5′-DM-2,2′-bipy=5,5′-dimethyl-2,2′-bipyridine) has been successfully synthesized via conventional solution method at room temperature. The complex is characterized by coordination titration analysis, elemental analysis, Infrared spectroscopy and powder X-ray diffraction. In addition, the structure of the complex was characterized by single crystal X-ray diffraction. The results reveal that complex is a binuclear molecular, crystallizing in the triclinic system Pī space group. Each binuclear unit contains two crystallographically independent Ho(Ⅲ), six 2,5-DClBA and two 5,5′-DM-2,2′-bipy ligands. The binuclear units are assembled into 1 D and 2 D supramolecular structures by C–H···Cl hydrogen bond and Cl-π interactions. Thermal behavior of the complex was determined by TG-DSC/FTIR techniques. The second thermal decomposition step for complex was calculated by integral iso-conversional nonlinear(NL-INT) method. The value of activation energy E varies slightly with α, indicating that the second decomposition stage of the title complex is single step reaction. Therefore, the improved double equal-double steps method is used to determine the mechanism function of the second thermal decomposition step of the complex. At the same time, the thermodynamic parameters(ΔH~≠, ΔG~≠and ΔS~≠) and kinetic parameters(activation energy E and the pre-exponential factor A) of the complex were also calculated. Heat capacity of the complex was measured by a DSC instrument.The experimental molar heat capacity can be fitted to the polynomial equation with the reduced temperature by the means of least square method. Based on the fitted polynomial and thermodynamic equations, the smoothed heat capacity, enthalpy and entropy were calculated.
The ternary lanthanide Ho(Ⅲ) complex, [Ho(2,5-DClBA)_3(5,5′-DM-2,2′-bipy)]2(2,5-DClBA=2,5-dichlorobenzoate; 5,5′-DM-2,2′-bipy=5,5′-dimethyl-2,2′-bipyridine) has been successfully synthesized via conventional solution method at room temperature. The complex is characterized by coordination titration analysis, elemental analysis, Infrared spectroscopy and powder X-ray diffraction. In addition, the structure of the complex was characterized by single crystal X-ray diffraction. The results reveal that complex is a binuclear molecular, crystallizing in the triclinic system Pī space group. Each binuclear unit contains two crystallographically independent Ho(Ⅲ), six 2,5-DClBA and two 5,5′-DM-2,2′-bipy ligands. The binuclear units are assembled into 1 D and 2 D supramolecular structures by C–H···Cl hydrogen bond and Cl-π interactions. Thermal behavior of the complex was determined by TG-DSC/FTIR techniques. The second thermal decomposition step for complex was calculated by integral iso-conversional nonlinear(NL-INT) method. The value of activation energy E varies slightly with α, indicating that the second decomposition stage of the title complex is single step reaction. Therefore, the improved double equal-double steps method is used to determine the mechanism function of the second thermal decomposition step of the complex. At the same time, the thermodynamic parameters(ΔH~≠, ΔG~≠and ΔS~≠) and kinetic parameters(activation energy E and the pre-exponential factor A) of the complex were also calculated. Heat capacity of the complex was measured by a DSC instrument.The experimental molar heat capacity can be fitted to the polynomial equation with the reduced temperature by the means of least square method. Based on the fitted polynomial and thermodynamic equations, the smoothed heat capacity, enthalpy and entropy were calculated.
引文
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