3-硝基邻苯二甲酸系列稀土配合物的光谱学与热稳定性研究

Spectroscopy and Thermostability of Series Rare-Earth Complexes with 3-Nitrophthalic Acid

在水-乙醇溶液中合成了稀土离子(RE=La,Nd,Eu,Tb,Er,Y)与3-硝基邻苯二甲酸(H2L)的晶体化合物,并通过元素分析、红外光谱、紫外光谱、差热-热重分析对系列配合物RE2L2(HL)2(H2O)6.2H2O进行了系统的研究与表征。谱学研究结果与通过X衍射表征的晶体结构数据是一致的。配体3-硝基邻苯二甲酸具有两种配位模式。两个全脱质子的配体L2-以桥联-螯合形式与两个稀土离子配位,而另两个单脱质子的配体HL-利用其酸根(—COO-)和羧基(—COOH)分别与金属离子以端基螯合形式配位。红外数据证实了羧酸根(—COO-)和羧基(—COOH)的存在以及羧基(—COOH)与结晶水之间的氢键作用。差热-热重数据与化合物的组成结构非常吻合,配合物中的结晶水和配位水在150℃左右开始失去并吸热,配体则在400℃左右开始氧化分解。

A series of rare-earth compound RE2 L2 （HL） 2 （H2O） 6 · 2H2O （RE= La, Nd, Eu, Tb, Er, Y） containing 3-nitrophthalic acid（H2L） ligand were synthesized from ethanol-water solution, and characterized and investigated by the element analysis, infrared and ultraviolet absorption spectra and different thermal-thermogravimetric analysis. The results of the spectroscopic analysis were conformed to the crystal structures determined by X-ray diffraction, showing that the carboxylate （-COO-） and carboxyl （-COOH） groups of the ligand link to the rare-earth ions by bridging and terminal mode respectively. Two rare-earth ions were linked by two di-deprotonated ligand L^2- in bridging-chelating mode to form a dinuclear structure, and coordinated by the other two mono-deprotonated ligands HL-in terminal chelating mode using their carboxylate （-COO） and carboxyl （- COOH） group together, respectively. The IR spectra shows the existence of the carboxylate （-COO-） and carboxyl （- COOH） group and the hydrogen bond interactions between the carboxyl （-COOH） group and crystal water. The DTA-TGA data were consistent with the composition of compounds, exhibiting an endothermic peak of the loss of the crystal and coordinated waters at about 150℃ and two exothermic peaks of the oxidation and decomposition of ligands in the rang of about 340 to 460℃.