Synthesis And Magnetic Properties Of The Complexes Based On Biphenyl-Tricarboxylic Acid

The synthesis and design of coordination polymers（CPs）have attracted widely concern and attention,due to the novel structures and the potential applications in optics,electricity,magnetism,adsorption and separation areas.As one of the researches,metal organic magnetic coordination polymers have been studied extensively both in China and abroad.In this paper,we are intended to design and synthetize new magnetic coordination polymers base on Co²⁺、Ni²⁺、Cu²⁺ ions and two kinds of biphenyl tricarboxylic acid ligands.Considering the synthesis process is influenced by a variety of reaction conditions,we obtained ten complexes by adding N-donate auxiliary ligands,adjusting the type and pH of solvent.Their structures are characterized by IR,element analysis and X-ray single crystal diffraction.In addition,we also studied the thermal stability and magnetic analysis after determing the purity by powder diffraction.The three main conclusions are given blow:1、We selected asymmetric rigid aromatic tricarboxylic acid 3,3’,5-bi-phyl tricarboxylic acid（3’-H3BPT）as the main ligand,N-donor linear ligands 4,4’-bipy and 1,4-bi（1 H-imidazol-1-yl）benzene respectively as auxiliary ligands to construct magnetic coordination polymer.In order to research the effect of metal ions on complexes,we kept the temperuture,solvents,ligands as the same and only added the different Ni²⁺,Co²⁺ ions.The structures and properties of the products are wholly different.It indicates that metal ion plays an important role on the construction of structures.Moreover,the structures show that 3’-carboxyl group of 3’-H3BPT was not dehydrogenation in the system with 1,4-bib as auxiliary ligand.While,in the system with 4,4’-bipy as auxiliary ligand,3’-carboxyl group of 3’-H3BPT dehydrogenized and coordinated with metal ions.Thus it is concluded that auxiliary ligands not only coordinated with metal ions but also may affect the ability of dehydrogenation of carboxylic ligands.Magnetostructural analyses indicate that ferromagnetic coupling in 1 and antiferromagnetic interactions in 2～4.2.The complexes 5 and 6 are based on the same Cu²⁺ ion,1,4-bib auxiliary ligand,solvents and temperature.The only difference between the two systerm is that 3,4’,5-biphenyl tricarboxylic acid in complex 5 and 3,3’,5-biphenyl tricarboxylic acid in complex 6.The 3D framework of 5 contains Cu+、Cu²⁺ ions,while the 2D framework of 6 only contains Cu²⁺ ions.The carboxyl groups of 4-H3BPT in 5 are wholly dehydrogenized.However,the carboxyl groups of 3’-H3BPT in 6 are similar with complex 1 and 2.Magnetostructural analyses indicate that ferromagnetic coupling in 5 and antiferromagnetic interactions in 6.3.Four Ni-cluster（Ni3、Ni4、Ni5、Ni7）based complexes were synthesized.The complexes 7 and 8 are constructed with same auxiliary ligand（2,2’-bipy）and reaction conditions.Then 4’-H3BPT and 3’-H3BPT were added in the reaction systems of 7 and 8,respectively.The 2,2’-bipy acts as terminal ligand to prevent the further extended to form 3D framework in 7.Compared with 8,complexes 9 was not adding auxiliary ligand（2,2’-bipy）.The complexes 8 and 9 are 2D and 1D structures,respectively.Thus,the 2,2’-bipy in the synthesis of complex 8 only acts as an environmental factor to regulate dehydrogenation of the carboxyl groups instead of coordination.In order to obtain complex with higher dimension,we added 1,4-bib and replaced the solvent with H2O/C2H5OH/DMF in the systerm of complex 9.Then complex 10 with 3D framework were obtained base on Ni7-cluster.This indicates that different metal cluster complexes can be obtained by controlling the auxiliary ligands and solvents.Magnetostructural analyses indicate that ferromagnetic coupling in 8～9 and antiferromagnetic interactions in 10.