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(mu(5)-H(2)hmIDC)(mu(2)-H2O)] (1), [Ba(mu(3)-H(3)hmIDC)(2)(mu(1)-H2O)](n) (2), [Ba(mu(5)-H(2)hmIDC)(mu(2)-O-2)(0.5)](n) (3), and [Ba(mu(3)-H(3)hmIDC)(mu(4)-H(3)hmIDC)](n) (4) were synthesized under the solvothermal conditions of 2-(hydroxymethyl)-1H-imidazole-4,5-dicarboxylic acid (H(4)hmIDC) with BaCl2 center dot 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 mu(5)-H(2)hmIDC(2-) pillars. This complex contains a unique alb network topology with the Schlafli 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 mu(3)-H(2)hmIDC(2-) ligands as 3-connected nodes. Complex 3 is a 3D framework formed with one-dimensional (1D) SBUs and mu(5)-H(2)hmIDC linkers, wherein the unprecedented oxygen molecules are coordinated using a linear-mu-eta(1):eta(1)-peroxo fashion, showing (5,6)-connected network topology with the Schlafli symbol (4(6).5(3).6)(4(6).5(4).6(5)). Complex 4 is a 3D framework based on 1D SBUs with mu(3)-H(3)hmIDC and mu(4)-H(3)hmIDC as linkers. This complex exhibits a trinodal (3,4,7)-connected 3D framework with the Schlafli 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.