Syntheses And Crystal Structures Of Substituted 1,4-benzenedicarboxylate Complexes

In the past decade, coordination polymers have been widely used in potential applications as new functional materials such as selective catalysis, molecular magnets and ligand exchange because of their various holes and channels in the structures, and have become one of the most current interests. In recent years, much attention has been focused on the use of 1,4-benzenedicarboxylic acid (H₂bdc) to design and synthesize numerous one-, two-, and three-dimensional metal-organic coordination networks, while limited research was devoted to substituted 1,4-benzenedicarboxylic acid (H₂sbdc). By contrast with the structures of the H₂bdc and the H₂sbdc, we have optimistic attitude towards the study of H₂sbdc, and the synthesis of complex, Zn₄O(cbdc)₃ (cyclobutyl-1,4-benzenedicarboxylic acid,H₂cbdc) , has greatly raised our interest in this kind of organic ligand. In this paper we have chosen 2-bromo-1,4-benzenedicarbosylic acid (H₂bbdc) and 2-nitro-benzene-1,4-dicarboxylate (H₂nbdc) as organic ligands and metal ion Cu(â…¡) as the coordinated centre to prepare six compounds, which are listed as follows:1. Copper chloride and 2-bromo-1,4-benzenedicarboxylic acid react with 2,2'-bipyridine under hydrothermal conditions in different pH solutions yield two complexes, namely Cu(Hbbdc)2(2,2'-bipy)] (1) and [Cu(bbdc)(2,2'-bipy)(H₂O)](2) . In the compound of 1, one carboxylic group does not coordinate with Cu(â…¡), while forms hydrogen bonding with uncoordinated carboxyl O atom. But in compound 2, the two carboxylic groups of the H₂bbdc both coordinate with Cu(â…¡) and give rise to a two-dimensional network.2. Copper salt and 2-nitro-1,4-benzenedicarboxylic acid react with 2,2'-bipy produce two novel compounds, namely [Cu(nbdc)(2,2'-bipy)(H₂O)]n (3) and [Cu₂(nbdc)₂ (2,2'-bipy)₂ (H₂O)₂].2H₂O (4) . Compound 3 is a two-dimensional network and different from the structure of 4, which is a dinuclear-copper complex. In both complexes bbdc ligands adopt very different coordination modes and give rise to two topological structures.3. Copper salt and 2-nitro-l,4-benzenedicarboxylic acid react with 1,10-phenanthroline in DMF by typical mixed solution technique lead to a tetra-nuclear compound, (Cu4(nbdc) 4 (phen)4(H2O) 4] 2.H2O(5), which is a novel ladder-like architecture. In the compound 5, two copper(II) atoms have different coordination geometries: one is a heavily distorted octahedron and the other is a square pyramidal. The structure can be further extended into two-dimensional hydrogen bonding network through coordinated and lattice water molecules. Compound 5 is a first tetra-nuclear structure constructed by 1,4-benzenedicarboxylates or their datives.4. An inorganic-organic hybrid material was synthesized and pure single crystalswere obtained by means of hydrothermal synthsis.The compound, [Cu2(OH)2(nbdc).H2O]n (6) , is a 3D layered pillared coordination polymer. In the framework, each Cu(II) adopts a square-pyramidal geometry. Hydroxyl groups exhibit bi-dentate and tri-dentate coordination modes and coordinate to copper atoms to assembly a 2-D hydroxyl layer. Bridging nbdc ligands connect layers into 3-D structure. The single-crystal structure of 6 is the first layered pillared 3D architecture constructed by 1,4-benzenedicarboxylates or their derivatives.