Synthesis, Structure And Properties Of Metal-Organic Coordination Polymers Based On 1H-benzimidazole-5, 6-dicarboxylic Acid

Metal-organic coordination polymers with interesting and rich topological structures can be easily tailored in structure and decorated in function. Due to the unique optical,electrical,magnetic and other properties,the materials based on coordination polymer have been extensively developed in potential applications of catalysis, sensing, hydrogen storage, gas adsorption, chiral catalysis, bio-simulation and molecular- recognition.Coordination polymer, also known as metal - organic coordination frameworks (metal-organic frameworks, MOFs), which is connected by coordination bonds between metal ions and organic ligands to form infinite one-dimensional to three-dimensional structure, is an important branch of crystal engineering and supramolecular chemistry. Furthermore, the study of coordination polymers is the frontier research of the coordination chemistry.According to the principles of supramolecular chemistry and crystal engineering, we take use of rigid benzimidazole dicarboxylate ligands and metal ions to build coordination polymers network with one-dimensiona chains, two-dimensional layers and three-dimensional supramolecular structures and study the functional properties of the title polymers. What'more, we study the influencing factors of preparing coordination polymers, controlling the reaction conditions and summing up the principles of synthesis to accumulate experimental data for the coordination polymer research. The first chapter briefly describes the following contents: the concepts and knowledges of metal-organic coordination polymers; outlining the research of coordination polymers; the ligand types of building coordination polymers; the topologies of coordination polymers; the functional material applications; the influencing factors of constructing coordination polymers; the main synthesis methods ; the research development of coordination polymers based on benzimidazole dicarboxylate ligand. We also have introduced the aims, significance and main results obtained in this paper.In the chapter II, we summarize the relevant study on coordination polymers constructed from the benzimidazole dicarboxylate ligand. After reading documents, we selecte rigid benzimidazole dicarboxylate ligand and Pb, Mg, Cd metal ions to design and synthesize four new coordination polymers [Pb(Hbidc)]n (1); [Cd(Hbidc)]n (2); [Mg(Hbidc)(H2O)5]·4H2O (3); [Mg(Hbidc)(H2O)4]n(4). The compound 1 is the first coordination polymer reported based on main group metal Pb ion and benzimidazole dicarboxylate acid ligand. Compound 1 has a two-dimensional layer structure and each H3bidc ligand in 1 loses two protons into Hbidc2-,in which the four atoms of six coordination atoms take theη2:η2:η1:η1:μ5 coordination mode to coordinate five lead metal centers and this new coordination mode of Hbidc2- ligand has not been reported up to now. Two ligands connect two Pb centers to form [Pb (Hbidc)]2 ring in compound 1. Compound 2 is a new coordination polymer with a two-dimensional layer structure constructed by left and right-handedness double helical chains. The studies of fluorescence show that compounds 1 and 2 have potential applications in the fluorescent materials. The compounds 3 and 4 are also the first report on coordination polymers constructed from Mg metal ion and benzimidazole dicarboxylate ligand and both two coordination polymers are zero-dimensional structure. The ligands in compounds 3 and 4 use a single N or O atom to coordinate with the metal centers, respectively.The chapter III, we reports a new heterometallic coordination polymer [CoCd2(C6H5O7)2(H2O)2]n (5). In compound 5, Co (II) metal center connects one-dimensiona-Cd-O-C-O- duoble chain into two-dimensional Cd2Co-citrate sandwich layered structure, rich hydrogen bonds extend two-dimensional layer structure into three-dimensional supramolecular structure. In the compound 5, the citric acid ligand adapt a new coordination mode (η1:η1:η1:η2:η1:η1:η1:μ4). The magnetic study shows that the anti-magnetic interaction occures in compound 5 and the potential application can be explored in magnetic material.In chapter IV, we choose metal ions U and V-like flexible organic ligand to successfully synthesize a novel coordination polymer [UO2 (oba) (H2O)]n (6) under hydrothermal condition. Compound 6 possesses a dimensional double chain structure. The H2oba ligand in compound 6 completely lose two protons forming oba2-, in which the two carboxyl adopt bidentate chelating, bidentate bridging coordination mode, respectively. The one-dimensional double chain structure is extended into three-dimensional supramolecular structure by hydrogen bonding interactions, and the coordination polymer 6 is of highly thermal stability .