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 -, and [Ba(μ 3 -H 3 hmIDC)(μ 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 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 Schlafi 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 Schlafi 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 Schlafi 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.

Syntheses, structures, and properties of three MOFs based on tertbutylphenyl imidazole dicarboxylate

“…The Cd-N distances are 2.271(2) and 2.333(3) Å and Cd-O lengths vary from 2.333(2) to 2.442(2) Å, comparable to previously reported values [25]. The bond angles around each Cd(II) vary from 67.02 (8) to 172.36 (9). Two nitrogens from each μ 3 -HBuPhIDC 2− bridge a four-membered ring, Cd1-O4-Cd1-O4, to form a 1-D zigzag chain.…”

“…Due to the ability and versatility of carboxylate and imidazole in forming strong coordination bonds and generating abundant structural motifs, a large number of MOFs with imidazole-4,5-dicarboxylic acid (H 3 IDC) or its two-position substituted derivatives have been reported [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. Among them, imidazole dicarboxylate ligands bearing two-position phenyl substituted groups have attracted much attention [18][19][20][21][22].…”

Crystal structure of diaqua-(2,2′-(butane-1,4-diyl)-bis(5-carboxy-1H-imidazole-4-carboxylato)-κ4 O,O′,N,N′)cadmium(II) monohydrate, C14H18O11N4Cd

“…We have successfully synthesised and reported two benzimidazole compounds [8,9]. Imidazole-4,5-dicarboxylic acid (H 3 IDC), a related compound, has provoked interest in coordination chemistry and served as multifunctional building block for a series of MOFs [10,11]. Their self-assemble process can be affected by factors, such as coordination environment of the metal centres counter anions etc.…”

“…Therefore, these complexes with different groups on the 2-position of the imidazole ring have been studied extensively [3]. However, structural modification of these MOFs requires further studies [10]. The asymmetric structure unit of the title compound contains one Cd(II), one ligand molecule, two coordinated water molecules and a free water molecule.…”

A novel heterometallic BaGa coordination polymer based on the bifunctional ligand 2,5-pyridine dicarboxylic acid

“…Note that the Ba(II) in 1 is only affinitive to O atoms. In the previously reported homometallic Ba-CPs such as those based on N-heterocyclic carboxylic acids, the Ba(II) ion was also affinitive to N atoms [21][22][23]. This means that the Ga(III) ion is more affinitive to N atom than Ba(II) ion and thus the bifunctional ligand H 2 pydc can successfully separate these two metal ions by different groups.…”