Study On Construction And Characterization Of Lanthanide Coordination Polymers With Isophthalic Acid Ligands

Substantial researches on lanthanide carboxylate complexes have been investigated in the last two decades with rapid development of single-crystal diffraction technique; however, most of which merely are with a view to single or sporadic studies. In this dissertation, we have constructed series of isophthalate lanthanide coordination polymers from the alterations of isophthalic acid ligand, and systemically studied the influence of the alterations on crystal structures of complexes. This dissertation divides into seven chapters and the main contents and conclusions are listed as following:1. Three series binuclear lanthanide carboxylate coordination polymers 1～7 have been synthesized under hydrothermal conditions by altering the length of carbon chains between carboxyl group and phenyl ring on ligands, which are isophthalic acid, 1,3-phenylenediacetic acid and 1,3-phenoxydiacetic acid, and lanthanide ions such as Pr³⁺, Eu³⁺and Ho³⁺. Several techniques, such as TG-DTG, IR spectrum and X-ray single crystal diffraction are used to analyze and characterize the structures of these complexes. From the structural analysis of three praseodymium complexes, we could draw a conclusion that as the dentate arms of carboxyl group on ligands elongating, the coordination numbers of Pr(III) and the coordination modes of ligands increase, and the mean distances between metallic atoms of metallic helices existing in these complexes augment.2. By altering 5-substituting group of isophthalic acid three series of lanthanide complexes 8～19 with 5-methylisophthalic acid and 5-nitroisophthalic acid have been prepared. In complexes 8～16 synthesized by hydrothermal method, most of the ligands adopt multidentate coordination modes joining several lanthanide ions into high-dimensional coordination polymers. And changing of 5-substituting group on isophthalic acid has a little effect on the coordinated abilities of the meta-carboxyl groups. Three 3D porous coordination polymers with formula of [Ln₂(5-NO₂-bdc)₃ (DMF)₄] (DMF)₂ (Ln = Nd (17), Dy (18). Ho (19)) have been prepared from DMF/EtOH mixing solvents, and adsorption experiments of 18 showed that they had larger potential pores with the value of 1214.4A³(23.8%) ,which means to be the 3rd dynamic porous metal-organic framework. 3. By adding and altering auxiliary ligands, we have got three series of lanthanide complexes 20～28 with 5-nitroisophthalic acid. As the distances between coordination sites of auxiliary ligands increasing, the distances between adjacent two-dimensional [Er(5-NO₂-bdc)₂]^- anion layers enlarged. As the bulks of auxiliary ligands largening, the coordination configuration of Er(III) optimized and the dimensions of coordination polymers increased. Furthermore, the one-dimensional complexes 26 and 28 with strongÏ€-Ï€packing interactions are prepared from DMF solvent, which indicates that the traditional solvent volatilizing method could bring low-dimensional complex.4. By measuring the enthalpy changes of the liquid phase formation reaction for complexes a^e, and calculating the electronic densities of five 5-substituted derivation of isophthalic acid, we can make a conclusion that 5-substituted group changing of the ligand has a little influence on oxygen atoms of carboxyl groups.5. Fluorescence experiments of these complexes indicated that they could be used for luminescence materials in future.6. Using packing saturation rule we calculated and analyzed these series of complexes, and the results showed that the changes of complexes with changes of ligands could be explained from the rule.