Construction of Ba(II) Coordination Polymers Based on Imidazole-Based Dicarboxylate Ligands: Structural Diversity Tuned by Alcohol Solvents

Four novel three-dimensional (3D) barium–organic coordination polymers formulated as [Ba­(μ₅-H₂hmIDC)­(μ₂-H₂O)]_<i>n</i> (<b>1</b>), [Ba­(μ₃-H₃hmIDC)₂(μ₁-H₂O)]_<i>n</i> (<b>2</b>), [Ba­(μ₅-H₂hmIDC)­(μ₂-O₂)_0.5]_<i>n</i> (<b>3</b>), and [Ba­(μ₃-H₃hmIDC)­(μ₄-H₃hmIDC)]_<i>n</i> (<b>4</b>) were synthesized under the solvothermal conditions of 2-(hydroxymethyl)-1<i>H</i>-imidazole-4,5-dicarboxylic acid (H₄hmIDC) with BaCl₂·2H₂O using a combination of water or dimethyl formamide (DMF) with various alcohol solvents (methanol, ethanol, <i>n</i>-propanol, isopropanol, and <i>n</i>-butanol). Complex <b>1</b> is a 3D framework based on two-dimensional secondary building units (SBUs) and μ₅-H₂hmIDC^2– pillars. This complex contains a unique <b>alb</b> network topology with the Schläfli symbol (4⁵·6)₂(4¹⁰·6¹⁴·8⁴). Complex <b>2</b> is a (3,10)-connected framework with binuclear [Ba₂(COO)₂] SBUs as 10-connected nodes and two types of μ₃-H₂hmIDC^2– ligands as 3-connected nodes. Complex <b>3</b> is a 3D framework formed with one-dimensional (1D) SBUs and μ₅-H₂hmIDC linkers, wherein the unprecedented oxygen molecules are coordinated using a linear-μ-η¹:η¹-peroxo fashion, showing (5,6)-connected network topology with the Schläfli symbol (4⁶·5³·6)­(4⁶·5⁴·6⁵). Complex <b>4</b> is a 3D framework based on 1D SBUs with μ₃-H₃hmIDC and μ₄-H₃hmIDC as linkers. This complex exhibits a trinodal (3,4,7)-connected 3D framework with the Schläfli symbol (4²·6)­(4³·6³)­(4⁸·6¹¹·8²). The results revealed that the alcohol solvent plays a subtle yet essential role in the crystallization and construction of Ba­(II)-organic coordination frameworks with diverse 3D structures, although these alcohol molecules do not appear in the frameworks