Two Pillared Three-Dimensional Inorganic/Organic Hybrid Structures Composed of Bimetallic Layers Bridged by Exo-bidentat
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Two Pillared Three-Dimensional Inorganic/Organic Hybrid Structures Composed of Bimetallic Layers Bridged by Exo-bidentate Ligands Long Pan, Xiaoying Huang, and Jing Li* Department of Chemistry, Rutgers University, Camden, NJ 08102, USA ABSTRACT The hydrothermal reactions of Cu(NO3)2·3H2O, K2CrO4 and exo-bidentate ligand bpy/bpe, (bpy = 4,4’-bipyridine, bpe = trans-1,2-bis(4-pyridyl)ethylene) result in two pillared 3D organic-inorganic hybrid compounds. Both contain bimetallic layers of copper(II) cations and chromate anions, which are directly connected by different organic ligands, leading to pillared structures with varying pillar length and thickness of layers. Crystal data for [Cu3(CrO4)2(OH)2(bpy)2] (1): triclinic, P1 , a = 5.358(1), b = 5.603(1), c = 13.515(3) Å, α = 81.78(3), β = 86.56(3), γ = 79.75(3)o, V = 394.91(13) Å3, Z = 1; [CuCrO4(bpe)] (2): monoclinic, C2/c, a = 23.282(5), b = 11.917(2), c = 9.726(2) Å, β = 112.99(3)o, V = 2484.2(8) Å3, Z = 8. INTRODUCTION Considerable efforts have recently been made to fabricate hybrid inorganic/organic materials, with a strong emphasis on their optimized functionality [1, 2]. One of the major challenges in this area is to design desired structures. The usual approach is to deliberately select suitable metal-containing inorganic fragments and organic ligands in consideration of their preferred coordination habit and possible geometry, as well as the ratio of the metal to the ligand. A reasonable strategy to build high dimensionality frameworks is realized by building pillared structures with organic pillars of changeable length and/or types to connect inorganic layers [3, 4]. The linear exo-bidentate ligands (e.g. pyrazine, 4,4'-bipyridine) as effective connectors or spacers have led to various interesting coordination structures, such as those of ladder, brick, and diamondoid [5]. While inorganic pillared layers composed of molybdenum or vanadium oxides have been found in several inorganic/organic hybrid frameworks, no 3D structures containing chromium oxides and organic pillars have been reported. To date, only one 2D structure with bimetallic layers (Cu/O/Cr) anchored with terminal pyridine ligands has appeared in the literature [6]. In this paper, we exploit the transformation of a 2D structure into a 3D one by replacing the terminal ligands with bidentate pillar molecules, which interconnect the 2D layers to give rise to a 3D network. EXPERIMENT SECTION Materials: Cu(NO3)2·3H2O, K2CrO4 trans-1,2-bis(4-pyridyl)ethylene (bpe), and 4,4’bipyridine (bpy) of reagent grade quality were used as purchased without further purification. Synthesis: [Cu3(CrO4)2(OH)2(bpy)2] (1): Hydrothermal reactions of Cu(NO3)2·3H2O (0.0242 g, 0.1 mmol), K2CrO4 (0.0097 g, 0.05 mmol), bpy (0.0156 g, 0.1 mmol) and 10 GG6.17.1
mL deionized water with the ratio of 1:0.5:1:5555 for 3 days at 150oC followed by slow cooling to room temperature produced orange plate crystals in 65% yield (0.010 g). [CuCrO4(bpe)] (2): Hydrothermal reactions of Cu(NO3)2·3H2O (0.0242 g, 0.1 mmol), K2CrO4 (0.0097 g,
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