Abstract In this work, structural, spectroscopical and thermal studies of lanthanum(III) and cerium(III) complexes with the 3,5-dimethoxybenzoate (DMBz) monocarboxylate ligand were performed. The metal-ligand minimum stoichiometry and polymeric arrangement of the complexes were respectively defined by TGA-DSC and X-ray powder diffraction as [M(DMBz)3.n]x, wherein “M” represents the lanthanides, “n” the water molecules in the lanthanum compound and “x” the basic unit of repetition in monoclinic polycrystalline system with space group P21/c. The products of the thermal decomposition of the material were also monitored by TGA-DSC/FT-IR both in air and N2 atmospheres in order to suggest the thermal decomposition mechanism. Theoretical calculations based in experimental results were performed to assess the coordination mode and spectroscopic properties of lanthanide complexes involving a monocarboxylate ligand. From theoretical calculations it was possible to generate FT-IR theoretical vibrational spectra and relate the level of correspondence to the experimental data inherent to the metal-ligand coordination mode. From the HOMO/LUMO orbitals obtained by TD-DFT calculations, the main electronic transitions responsible for the absorption and emission bands of the complexes were determined.

中文翻译：

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结合 X 射线衍射/Rietveld 方法、FT-IR 和 UV-Vis 光谱的热分析：镧和铈 (III) 多晶配合物的结构表征

摘要 在这项工作中，对镧 (III) 和铈 (III) 配合物与 3,5-二甲氧基苯甲酸酯 (DMBz) 单羧酸盐配体进行了结构、光谱和热学研究。配合物的金属配体最小化学计量和聚合物排列分别通过TGA-DSC和X射线粉末衍射定义为[M(DMBz)3.n]x，其中“M”代表镧系元素，“n”代表水镧化合物中的分子，“x”是空间群为P21/c的单斜多晶系中重复的基本单位。材料的热分解产物也在空气和 N2 气氛中通过 TGA-DSC/FT-IR 进行监测，以表明热分解机制。进行基于实验结果的理论计算以评估涉及单羧酸盐配体的镧系元素配合物的配位模式和光谱特性。根据理论计算，可以生成 FT-IR 理论振动光谱，并将对应水平与金属配体配位模式固有的实验数据联系起来。从通过 TD-DFT 计算获得的 HOMO/LUMO 轨道，确定了负责复合物吸收和发射带的主要电子跃迁。