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

Abstract

Four novel three-dimensional (3D) barium–organic coordination polymers formulated as [Ba(μ 5 -H 2 hmIDC)(μ 2 -H 2 O)] n ( 1 ), [Ba(μ 3 -H 3 hmIDC) 2 (μ 1 -H 2 O)] n ( 2 ), [Ba(μ 5 -H 2 hmIDC)(μ 2 -O 2 ) 0.5 ] n ( 3 ), and [Ba(μ 3 -H 3 hmIDC)(μ 4 -H 3 hmIDC)] n ( 4 ) were synthesized under the solvothermal conditions of 2-(hydroxymethyl)-1 H -imidazole-4,5-dicarboxylic acid (H 4 hmIDC) with BaCl 2 ·2H 2 O using a combination of water or dimethyl formamide (DMF) with various alcohol solvents (methanol, ethanol, n -propanol, isopropanol, and n -butanol). Complex 1 is a 3D framework based on two-dimensional secondary building units (SBUs) and μ 5 -H 2 hmIDC 2– pillars. This complex contains a unique alb network topology with the Schläfli symbol (4 5 ·6) 2 (4 10 ·6 14 ·8 4 ). Complex 2 is a (3,10)-connected framework with binuclear [Ba 2 (COO) 2 ] SBUs as 10-connected nodes and two types of μ 3 -H 2 hmIDC 2– ligands as 3-connected nodes. Complex 3 is a 3D framework formed with one-dimensional (1D) SBUs and μ 5 -H 2 hmIDC linkers, wherein the unprecedented oxygen molecules are coordinated using a linear-μ-η 1:η 1 -peroxo fashion, showing (5,6)-connected network topology with the Schläfli symbol (4 6 ·5 3 ·6)(4 6 ·5 4 ·6 5 ). Complex 4 is a 3D framework based on 1D SBUs with μ 3 -H 3 hmIDC and μ 4 -H 3 hmIDC as linkers. This complex exhibits a trinodal (3,4,7)-connected 3D framework with the Schläfli symbol (4 2 ·6)(4 3 ·6 3 )(4 8 ·6 11 ·8 2 ). 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.