Lanthanide coordination compounds with 1H-benzimidazole-2-carboxylic acid: syntheses, structures and spectroscopic properties
Lanthanide coordination compounds with 1H-benzimidazole-2-carboxylic acid: syntheses, structures and spectroscopic properties
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DOI：
10.1039/c2ce26120k
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发表时间：
2013
期刊：
影响因子：
3.1
通讯作者：
Zhengqiang Xia;Q. Wei;Qi Yang;Chengfang Qiao;Sanping Chen;G. Xie;Guochun Zhang;Chunsheng Zhou;Sheng-li Gao
中科院分区：
文献类型：
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作者：
Zhengqiang Xia;Q. Wei;Qi Yang;Chengfang Qiao;Sanping Chen;G. Xie;Guochun Zhang;Chunsheng Zhou;Sheng-li Gao
在水热条件下，合成了一种柔性多齿配体1H-苯并咪唑-2-羧酸，并以此构建了一系列镧系配位聚合物[Ln（HBIC）3]n（Ln = Eu（1），Tb（2），Gd（3），Pr（4），Nd（5）; H2 BIC = 1H-苯并咪唑-2-羧酸）.通过元素分析、红外光谱、单晶X射线衍射、热分析和各种光谱技术对所有化合物进行了表征。结构分析表明，它们是同构的，具有扭曲网格的二维波浪状层状结构，其中相邻的Ln 3+中心通过两种新的配位模式被HBIC−配体桥接，相邻的HBIC−配体通过两种不同的层内氢键紧密结合.相邻的2D层通过强的层间氢键环基序R22（10）进一步互连以产生3D超分子结构。光学性质研究表明，化合物1、2、4和5在室温下均表现出相应镧系离子在可见或近红外区的特征发光带。特别地，由于H2 BIC配体的最低三重态能级与Tb 3+的5D4态能级之间的理想能隙，化合物2在固态下显示出明亮的绿色发光，具有令人满意的1.2ms的5D4寿命和31%的高总量子产率。并对化合物1和2的能量转移机理进行了讨论。
A flexible multidentate ligand, 1H-benzimidazole-2-carboxylic acid, was synthesized to construct a series of lanthanide coordination polymers [Ln(HBIC)3]n (Ln = Eu (1), Tb (2), Gd (3), Pr (4), Nd (5); H2BIC = 1H-benzimidazole-2-carboxylic acid) under hydrothermal conditions. All the compounds were fully characterized by elemental analysis, IR spectroscopy, single-crystal X-ray diffraction, thermal analysis and various spectroscopic techniques. Structural analyses reveal that they are isostructural and feature a 2D wave-like layer structure with distorted grids, in which the adjacent Ln3+ centers are bridged by the HBIC− ligands with two kinds of new coordination modes and the adjacent HBIC− ligands are tightly bound by two types of distinct intra-layer hydrogen bonds. The adjacent 2D layers are further interconnected by strong inter-layer hydrogen bond ring motifs R22(10) to generate a 3D supramolecular architecture. Optical studies indicate that the compounds 1, 2, 4 and 5 exhibit characteristic luminescence emission bands of the corresponding lanthanide ions in the visible or near-infrared regions at room temperature. In particular, compound 2 displays bright green luminescence in the solid state with a satisfactory 5D4 lifetime of 1.2 ms and a high overall quantum yield of 31%, due to an ideal energy gap between the lowest triplet state energy level of H2BIC ligand and the 5D4 state energy level of Tb3+. The energy transfer mechanisms in compounds 1 and 2 were also described and discussed.