Preparation, characterization, and properties of two rare earth organic frameworks with 1H-benzimidazole-2-carboxylic acid

Abstract

Reaction of rare earth metal ions with 1H-benzimidazole-2-carboxylic acid (H₂BIC) acid yielded two rare earth organic frameworks [Ln(HBIC)₃] _n (Ln = Gd 1, Y 2; H₂BIC) under hydrothermal conditions. Both compounds were structurally characterized by single-crystal X-ray diffraction. Their thermal stabilities, luminescent, and magnetic properties were also investigated. Compounds 1 and 2 are isomorphic and present 2-D networks constructed by bridging-chelating HBIC⁻ linkers and rare earth cation nodes, in which each asymmetric unit consists of one crystallographically unique Ln(III) ion and three HBIC⁻ with two kinds of coordination modes. The two compounds exhibit high-thermal stability, stable to 320 °C. Antiferromagnetic interactions between Gd(III) centers for 1 were observed from magnetic susceptibility data. 2 exhibits a strong blue emission band in the solid state.

Keywords:

• Rare earth organic frameworks
• 1H-Benzimidazole-2-carboxylic acid
• Antiferromagnetic interaction
• Luminescence

Acknowledgments

We gratefully acknowledge the financial support from the National Natural Science Foundation of China (Grant nos. 21073142, 21173168, 21273171 and 21127004), the Natural Science Foundation of the Department of Education of Shaanxi Province (Grant nos. 11JS110, 2010JK882, 2010JQ2007, 08JK459 and 11JK0578) and the Natural Science Foundation of Shangluo University (Grant no. 12SKY012).