Source of materialThe mixtures of 4-carboxyphenylacetic acid (H 2 htpa, 0.1 mmol, 18.7 mg), 1,2-di(4-pyridyl)ethylene (bpe, 0.2 mmol, 36.8 mg), Ni(OAc) 2 ·4H 2 O (0.1 mmol, 24.8 mg), and ethanol (3.5 ml), H 2 O (3.5 ml) were sealed in a 23 ml Teflon-lined stainless steel autoclave, heated to 393K for 4 days, and then slowly cooled down to room temperature for crystallization. Green block-shaped crystals of the title compound were obtained. DiscussionInorganic-organic hybrid coordination polymeric frameworks have been widely studied, due to their potential application in the fields of magnetism, fluorescence, catalysis etc [1][2][3][4][5][6]. It is well known that organic ligands play crucial roles in the design and construction of desirable frameworks. Multi-carboxylate ligands combined with rigid and flexible carboxylate groups display unpredictable structure types, which can probably be attributed to very abundant coordination modes [7][8]. With the aim of the understanding of the coordination chemistry of flexible aromatic multi-carboxylate complexes, we have chosen 4-carboxyphenylacetic acid as a bridging ligand to construct new coordination polymers. Single-crystal X-ray analysis shows that the title compound is a 1D chain structure. The asymmetric unit contains one Ni(II) cation, one completely deprotonated htpa anions, one bpe molecule, two coordinating waters and one uncoordinated water as shown in Fig. 1. In this complex, the nickel atom is six-coordinated in a distorted octahedral manner [NiN 2 O 4 ] by two N atoms from two bpe ligands, two oxygen atoms from one htpa anions and two coordinating water molecules, with respective bond lengths of 2.0866(17), 2.1109 (17)

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Source of materialThe mixtures of 4-carboxyphenylacetic acid (0.2 mmol, 37.4 mg), 1,3-di(pyridin-4-yl)propane (bpp) (0.1 mmol, 19.8 mg), Co(OAC) 2 ·4H 2 O (0.1 mmol, 24.9 mg), NaOH (0.1 mmol), and H 2 O (7.0 ml) were placed in a 23 ml Teflon lined stainless steel reactor. The vessel was heated to 393K for 4 days, and then slowly cooled to room temperature. Brown, block-shaped crystals were obtained, crystals were filtered off, washed with mother liquid, and dried under ambient conditions. Discussion Metal-organic frameworks (MOFs) with well-regulated network structures have provoked significant interest as functional materials displaying potential applications in such fields as magnetism, molecular separation, catalysis, luminescence, and molecule storage [1][2][3][4][5]. Aromatic multi-carboxylate ligands are good candidates for the construction of the layers, wherein diverse binding modes of the carboxylates help enhance the robustness of metalcarboxylate networks [6,7]. Dipyridyl-type ligands are desired pillar spacers, which can allow easy control of channel dimensions between the metal-carboxylate layers. The key to synthesize MOFs with permanent porosity is to prevent the disruption of framework integrity even after guest elimination. Though the reports concerning this aspect are emerging, it has still been a tremendous challenge to obtain the dynamic microporous MOFs [8,9]. The asymmetric unit of the title complex contains one 1,3-di(pyridin-4-yl)propane (bpp) ligand, one-half Co ion, one 2-(4-carboxyphenyl)acetato ligand and one coordinated water molecule as shown in Fig.