基于1H-苯并咪唑-2-羧酸的三个镧系超分子化合物的结构、热分解动力学和荧光性质

在水热条件下合成了三个镧系超分子化合物Ln(HBIC)₃]_n Ln=Sm (1), Ho (2), Yb (3); H₂BIC=1H-苯并咪唑-2-羧酸], 其中化合物1、2呈单晶态, 化合物3则为粉末样品; 借助单晶X射线衍射(XRD)、粉末衍射、元素分析、红外(IR)光谱、热分析等手段对化合物进行了表征. 结构分析表明, 1-3为同构化合物, 都呈现二维的平面结构, 其中每一个镧系金属中心与来自五个HBIC^-配体的三个氮原子和五个氧原子以两种新的配位模式配位形成一个轻微扭曲的双帽三棱柱几何构型, 相邻的二维(2D)平面进一步通过强的氢键作用形成了一个三维(3D)的超分子结构. 热重分析结果表明, 化合物1-3在360 ℃前均保持稳定, 呈现出良好的热稳定性. 基于Kissinger和Ozawa-Doyle两种方法, 通过差示扫描量热(DSC)技术研究得到了化合物1热分解的动力学参数(指前因子A_K=1.286×10⁸ s^-1; 活化能E_K=199.3 kJ·mol^-1, E_O=205.2 kJ·mol^-1). 另外, 也研究了室温下化合物1和3的固态发光性能, 结果表明, 化合物1和3分别在可见光区和近红外光区呈现出相应镧系金属离子的特征发射.

Structures,Thermodecomposition Kinetics and Luminescence Properties of Three Lanthanide-Based Supramolecular Compounds with 1H-Benzimidazole-2-carboxylic Acid

Three lanthanide-based supramolecular compounds, Ln(HBIC)₃]_n Ln=Sm (1), Ho (2), Yb (3); H₂BIC=1H-benzimidazole-2-carboxylic acid], were hydrothermally synthesized and structurally characterized by X-ray single crystal diffraction (compounds 1 and 2), powder X-ray diffraction (XRD) (compound3), elemental analysis, infrared (IR) spectroscopy, and thermal analysis. Structural analyses reveal that compounds 1-3 are isomorphous and display a two-dimensional (2D) plane, in which each lanthanide center is coordinated by three N and five O atoms from five flexible HBIC^- ligands with two kinds of new coordination modes, giving rise to a slightly distorted two-capped triangle prism geometry. The 2D square networks are further assembled into a three-dimensional (3D) supramolecular framework through strong hydrogen-bonding interactions. Thermogravimetry analyses (TG) indicate that compounds 1-3 exhibit good thermostability and could be stable up to 360℃. By means of differential scanning calorimetry (DSC) techniques, the thermoanalysis kinetics parameters of the thermodecomposition of compound 1 were calculated by the Kissinger''s and Ozawa-Doyle''s methods; the pre-exponential factor A_K was 1.286×108 s^-1 and the apparent activation energy E_K and E_O were determined to be 199.3 and 205.2 kJ·mol^-1, respectively. In addition, the luminescent properties of compounds 1 and 3 were also studied at room temperature in the solid state. The results reveal that compounds 1 and 3 exhibit characteristic emission bands of the corresponding lanthanide ions in the visible and near-infrared regions, respectively.