Issue 1, 2013

Lanthanide coordination compounds with 1H-benzimidazole-2-carboxylic acid: syntheses, structures and spectroscopic properties

Abstract

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.

Graphical abstract: Lanthanide coordination compounds with 1H-benzimidazole-2-carboxylic acid: syntheses, structures and spectroscopic properties

Supplementary files

Article information

Article type
Paper
Submitted
10 Jul 2012
Accepted
26 Sep 2012
First published
03 Oct 2012

CrystEngComm, 2013,15, 86-99

Lanthanide coordination compounds with 1H-benzimidazole-2-carboxylic acid: syntheses, structures and spectroscopic properties

Z. Xia, Q. Wei, Q. Yang, C. Qiao, S. Chen, G. Xie, G. Zhang, C. Zhou and S. Gao, CrystEngComm, 2013, 15, 86 DOI: 10.1039/C2CE26120K

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