| The coordination polymers have novel structure, unique properties and potential application value in many fields such as luminescence,adsorption separation, gas storage and heterogeneous catalysis, which has aroused the attentions of chemists and becomes one of the hot fields in contemporary chemistry research. However, the synthesis of coordination polymers with specific topologies requires the selection of suitable ligands, metal centers and the availability of specific synthetic routes. Therefore, the design and construction of the coordination polymers are still the main challenges in this field.Since the carboxyl oxygen of the carboxylic acid ligands can provide a wide range of coordinations. These ligands have been widely used in the synthesis of coordination polymers. The rigid carboxylic acid ligands with benzene ring are much easier to obtain metal organic framework materials with channels than others, which is one of the most widely used ligands in recent years. And now a single ligand gradually can not meet our precise understanding of the structure of the complex requirements. Thus a series of mixed ligands are applied to the same reaction system. A class of coordination polymers have been successfully synthesized through different lengthes of the connectors and a variety of coordinations. Therefore, in this paper we have chosen a class of carboxylic acid ligands such as 2,6-pyridinedicarboxylic acid(2,6-H2PDC), 3,5-pyridinedicarboxylic acid (3,5-H2PDC),2,5-dibromoterephthalic acid (2,5-H2Br2BDC), 2-hydroxypropionic acid(Lac) and bromoacetic acid (BrMA), which were mixed with different metal ions under the conditions of solvent heat or volatilization. Eleven kinds of novel coordination polymers were synthesized. Meanwhile their structures and properties were studied. This paper mainly includes the following two aspects:1. Three kinds of coordination polymers [Zn2(2,6-PDC)2] (1),[CaPb6(2,6-PDC)6]Cl2 (2) and [Mg1.5Ce(2,6-PDC)3(H2O)3]·3.5H2O(3)were synthesized by the addition of the complexes of 2,6-H2PDC and 3,5-H2PDC, reacting with Mg,Ca, Zn, Ba and Ce. In the complex 1, the ligand was chelated to the metal center forming a two-dimensional lamellar structure, while the ligand 3,5-H2PDC did not participate in the coordination. The calcium ion in complex 2 first forms an octahedral secondary building block and then forms a two-node 3,18-connected?4,}6{442?672?839} topological structure with lead ions . Only the ligand 2,6-H2PDC involveds in the coordination reaction. Complex 3 is a three-dimensional channel structure of binary nuclei, which is alternately arranged in the form of a …ABAB….Although the ligand 3,5-H2PDC did not participate in the reaction in the above complexes. The effect of the acid-base regulator was prayed by it. We have tested their thermal stability for the coordination polymers with pores. We also examined their properties for the adsorption and resolution of iodine molecules for the consideration of their voids.2. The main rigid rod-like carboxylic acid ligand 2,5-H2Br2BDC and three kinds of auxiliary carboxylic acid ligands Lac, BrMA and 3,5-H2PDC were used to react with alkaline earth metal Ca, Ba,transition metal Fe, Zn, rare earth metal La, Eu and main group metal Pb.We obtained eight coordination polymers by solvothermal method and volatilization at room temperature. However the 8 coordination polymers only containes the main ligand 2,5-H2Br2BDC. The results indicated that the three auxiliary carboxylic acid ligands might only play a role in adjusting pH. Using lactic acid as an auxiliary carboxylic acid ligand,four complexes [Zn(Br2BDC)(DMF)] (4) ,[Fe2(Br2BDC)2(DMF)3](5),[Ba(Br2BDC)(DMF)(H2O)] (6) and [Pb(Br2BDC)(DMF)](7)were obtained. The complex 4 is a two-dimensional network structure formed by the trapezoidal chain in the parallel ab plane with the arrangement of …ABAB …. The complex 5 is a three-dimensional frame structure with three types of channels composed of one-dimensional directional channels and a 41-helical chain through a shared metal node. Complex 6 is a three-dimensional metal organic framework with pcu topology.Complex 7 is a three-dimensional frame structure composed of a brick-walled two-dimensional network as a pillar through Br2BDC ligands. Other three complexes[Ba2(HBr2BDC)2(Br2BDC)(DMF)2(H2O)2](8),[La2(Br2BDC)3(DMF)2(H2O)2]·2DMF(9) and[Eu2(Br2BDC)3(DMF)2(H2O)2]·2DMF(10) were obtained with the use of bromoacetic acid as an auxiliary ligand. The complex 8 is a three-dimensional framework with two one-dimensional channels along the a-axis direction. The structures of complex 9 and 10 are similar and are all metal organic frameworks with double-core metal as a node along the b-axis direction. Only complex [Ca2(Br2BDC)2(DMF)2(H2O)2] (11)were obtained by using rigid 3,5-pyridinedicarboxylic acid as the auxiliary ligand. The structure of the complex 11 is a two-dimensional self-interpenetrating nbo-type three-dimensional frame structure. These results indicate that the diverse bridging patterns of ligand Br2BDC contribute to the construction of diverse structures. |
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