Two novel 2D and 3D coordination polymers constructed from pyrazine-2,3-dicarboxylic acid and chloride bridged secondary building units

The synthesis, spectroscopic properties and crystal structures of {[Cu2(μ-Cl)2(μ3-Hpzdc)(Cl)(H2O)2]·1.5H2O}n (1) and {[Cd(μ-Cl)(μ-Hpzdc)]·H2O}n (2) complexes were reported (H2pzdc = pyrazine-2,3-dicarboxylic acid). H2pzdc is singly deprotonated in both complexes and the coordination mode of Hpzdc ligand in 1 has been first reported in this presentation. The complex 1, which has a 3D framework structure, was formed with double μ-chloride and μ3-Hpzdc bridges. In 1, water molecules occupy in the 1D channel as guest molecules. Furthermore, unprecedented 1D hybrid water–chloride anionic [(H2O)8Cl2]n cluster has been structurally identified. In the complex 2, the Cd(II) atom is seven-coordinated by two hydrogen pyrazine-2,3-dicarboxylate, two chloride and one aqua ligands in a distorted monocapped octahedral coordination geometry. The Cd(II) atoms are bridged by the bis(bidentate) Hpzdc ligands, forming 1D polymer chain. The adjacent 1D chains are linked each other through the double chloride bridges to form 2D layer. The layers are connected together through O–H⋯O interactions resulting in a three-dimensional framework. The mechanisms for these compounds were validated by density functional theory (DFT) calculations on the experimental geometries. The photoluminescent property of 2 was investigated in the solid state at room temperature. Moreover, in order to assess the potentials of 1 and 2 in gas storage applications, we performed atomically detailed simulations.

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► Two novel 3D and 2D MOF architectures of Cu(II) and Cd(II)-hydrogenpirazine-2,3-dicarboxylate complexes have synthesized and characterized.
► The Hpzdc ligand acts as a bridging ligand with two different bridging modes and it exhibits a new coordination mode.
► 1D hybrid water–chloride anionic [(H2O)8Cl2]n cluster has been identified.
► The complex 2 shows strong peaks with the emission at 540 and 595 nm.