Crystal Engineering And Magnetic Property Of Benzenedicarboxylic Acid-based Coordination Polymers

According to the principle of crystal engineering,this thesis selects benzenedicarboxylic acid derivatives with multiple coordination sites as organic ligands to react with transition metals(Co²⁺,Cu²⁺)and lanthanide（Ln）ions（Ln=La,Ce,Pr,Nd,Gd）,respectively.By adjusting the reaction conditions such as the ratios of metal ions and organic ligands,solvent,reaction time and temperature,etc.,we obtained three series of benzenedicarboxylic acid-based coordination polymers（CPs）and investigated their magnetic properties.1.When react benzimidazole dicarboxylic acid（H₃bidc）with different metal ions under hydrothermal conditions by adjusting the types of metal ions,temperature,p H,and reactant ratios,two three-dimensional（3D）CPs were harvested,{[Co（Hbidc）]H₂O}_n（1）and{[Gd（Hbidc）（ox）_0.5H₂O]·H₂O}_n（2）.Single-crystal structure analyses show that each Co²⁺in 1adopts a four-coordinate tetrahedral configuration,which is bridged by H₃bidc ligands to form a 3D 4-connected‘sra’-type topology.Magnetic property of 1 indicates that antiferromagnetic interactions exist in the adjacent Co²⁺.In 2,adjacent Gd³⁺ions are connected by H₃bidc ligand to form a 2D layer,which further linked by H₂ox ligand to generate a 3D framework.Magnetic result suggests that the presence of antiferromagnetic interactions in adjacent Gd³⁺ions in 2,moreover,2 exhibits a significant magnetocaloric effect（MCE）with the maximum–ΔS_m value of 35.9 J·kg^–1·K^–1 at 2.0 K for an applied field of 70 k Oe.2.Using 5-aminoisophthalic acid and 1,2,4,-trimellitic anhydride to synthesize an example of isophthalic acid imide derivative ligand H₃phca,and then assembling with Ln³⁺ions to produce a series of 3D Ln-CPs,{[Ln（phca）（DMF）（H₂O）]·H₂O}_n（Ln=La for 3,Ce for4,Pr for 5,Nd for 6,and Gd for 7）.Structural analyses demonstrate that adjacent Ln³⁺ions are bridged by H₃phca ligands to form 3D frameworks.Meanwhile,the magnetic properties of 3-7 have been evaluated.Magnetic result of 7 indicates that weak antiferromagnetic coupling interactions exist adjacent Gd³⁺ions,furthermore,it presents an obvious low-temperature MCE.3.The self-assembled reactions of 5-aminodiacetic isophthalic acid（H₄adip）ligand and Cu²⁺ions under different temperatures to produce two 1D CPs,{[Cu（H₂adip）（H₂O）]·5H₂O}_n（8）and[Cu₂（adip）（H₂O）₃]_n（9）.Structural analyses reveals that adjacent Cu²⁺ions in 8 are interconnected by H₄adip ligands to give a 1D zigzag chain,while neighbouring Cu²⁺ions in9 are linked by H₄adip ligands to produce a 1D double chain.Moreover,both 8 and 9 could be further stacked to present the 3D supramolecular architectures through hydrogen bonds.Interestingly,the block crystal 8 can undergo structural transformation to form the sheet crystal 9 when heated and held 8 at 80℃ for 12 h.Both 8 and 9 exhibited ferromagnetic coupling interactions between Cu²⁺ions...