Synthetic Metals 161 (2011) 2471–2480 Contents lists available at SciVerse ScienceDirect Synthetic Metals journa l h o me page: www.elsevier.com/locate/synmet Two novel 2D and 3D coordination polymers constructed from pyrazine-2,3-dicarboxylic acid and chloride bridged secondary building units Günes ¸ Günay a,b , Okan Zafer Yes ¸ ilel a,∗ , Mustafa Serkan Soylu c , Seda Keskin d , Hakan Dal e a Department of Chemistry, Faculty of Arts and Sciences, Eskis ¸ ehir Osmangazi University, TR-26480 Eskis ¸ ehir, Turkey b Graduate School of Science, Eskis ¸ ehir Osmangazi University, 26480 Eskis ¸ ehir, Turkey c Department of Physics, Faculty of Arts and Sciences, Giresun University, Giresun, Turkey d Department of Chemical and Biological Engineering, Koc ¸ University, ˙ Istanbul, Turkey e Department of Chemistry, Faculty of Science, Anadolu University, 26470 Eskis ¸ ehir, Turkey a r t i c l e i n f o Article history: Received 5 July 2011 Received in revised form 16 September 2011 Accepted 20 September 2011 Available online 15 October 2011 Keywords: Pyrazine-2,3-dicarboxylic acid Pyrazine-2,3-dicarboxylate complexes Metal-organic framework Water–chloride clusters a b s t r a c t The synthesis, spectroscopic properties and crystal structures of {[Cu 2 (-Cl) 2 ( 3 - Hpzdc)(Cl)(H 2 O) 2 ]·1.5H 2 O} n (1) and {[Cd(-Cl)(-Hpzdc)]·H 2 O} n (2) complexes were reported (H 2 pzdc = pyrazine-2,3-dicarboxylic acid). H 2 pzdc 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 -chloride and  3 -Hpzdc bridges. In 1, water molecules occupy in the 1D channel as guest molecules. Furthermore, unprecedented 1D hybrid water–chloride anionic [(H 2 O) 8 Cl 2 ] 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. © 2011 Elsevier B.V. All rights reserved. 1. Introduction The design and synthesis of porous coordination polymers have received enormous attention. These compounds have been extensively studied in the past decade because of their potential applications in various areas such as host–guest chemistry [1], molecular separation [2–4], sensors [5,6], electrical conductivity [7], magnetism [8], gas storage [9], and catalysis [10]. Until now, a large number of one-, two- and three-dimensional coordination polymers have been obtained through the judicious selection of multifunctional ligands, suitable metal ions and reaction condi- tions [11,12]. It is known that aromatic carboxylates as a kind of multifunctional ligands play an important role in coordination chemistry. In particular, polycarboxylate ligands have been shown to be good building blocks in the design of metal-organic materials with desired topologies due to their rich coordination modes. For example, the aromatic polycarboxylate ligands, such as ∗ Corresponding author. Tel.: +90 222 2393750; fax: +90 222 2393578. E-mail address: yesilel@ogu.edu.tr (O.Z. Yes ¸ ilel). pyridine-, pyrazole-, pyrazine-, imidazole- and benzene- carboxylates have been widely used to construct different coordination polymers because of the diversity of coordination modes and sensitivity to pH values of the carboxylate group. Among them, the synthesis and characterization of complexes based on pyrazine-2,3-dicarboxylic acid has evolved rather rapidly in recent years. Pyrazine-2,3-dicarboxylic acid with multifunc- tional coordination modes can be partially or fully deprotonated to generate Hpzdc - , and pzdc 2- anions at different pH values [13,14]. The Hpzdc ligand coordinates to metal ions via its two carboxyl groups and two nitrogen atoms of the pyrazine ring. Various possi- ble coordination modes for the Hpzdc ligand (Scheme 1) have been reported. In addition to the most observed coordination modes, the Hpzdc ligand exhibits a new coordination mode in the complex 1. In recent years, some complexes with pyrazine-2,3-dicarboxylic acid have been reported [15–20]. While compared with dian- ionic pzdc complexes, mixed-ligand coordination polymers with monoanionic Hpzdc has been rarely presented up to now [21,22]. Furthermore, in the last few decades dinuclear and polynu- clear Cu(II) and Cd(II) complexes with M(-Cl) 2 M (M = Cu(II) and Cd(II)) core have been extensively studied [23–25]. However, a few 0379-6779/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.synthmet.2011.09.033