Synthesis And Magnetic Properties Of Low Dimensional Molecular Magnets Based On Quinoline-based Polycarboxylic Acid Ligands

Molecule-based magnetic materials have attracted much attention due to their advantages of good solubility,light weight,small size,strong plasticity,and good chemical controllability.Among them,single-molecule magnets and single-chain magnets with slow relaxation behaviors are the hot spots in the field of molecule-based magnets.Such magnets not only have magnetic hysteresis effect?the classical effect of macroscopic magnets?when the temperature is lower than the blocking temperature,but also have quantum effects such as quantum tunneling and quantum phase interference.Because of these unique properties,molecule based magnets have potential applications in molecular spin,quantum computing,and high-density information storage.Although a lot of single molecule magnet materials based on transition or rare earth metals have been reported,the structure-magnetic property relationships and the mechanism are still not well understood.On the other hand,the long-term goal of scientists in the field of single molecule?ionic?magnet materials are still to realize its real application value,mainly focusing on improving the relaxation barrier and blocking temperature.This dissertation starts from the design and synthesis of molecule based magnetic materials.Magnetic and HF-EPR measurements were employed to analyze the structure-magnetic property relationship.The main contents are as follows:1.On the basis of previous studies,8-carboxymethoxy-2-carboxylicquinoline ligands?quinoline polycarboxylic acid ligands?were designed and synthesized.Mononuclear structures?{[M?L??H₂O?₃]}·H₂O?M=Mn?1?,Co?2??,[Ni?L??H₂O?₂]?3??and one-dimensional chain structures({[M?L??H₂O?]}_n?M=Ni?4?,Cu?5??were synthesized by the solvothermal reactions.2.X-ray diffraction?XRD?pattern shows the high purity of the samples.Magnetic and HF-EPR studies prove that compound 2 has large and positive zero-field splitting(D=+70.4 cm^-1).The magnetic studies of 4 and 5 indicate that there are weak anti-ferromagnetic exchanges between M^II-M^II?the J values are 1.50 K and3.55 K for 4 and 5,respectively?.From the results of HF-EPR,4 can be considered as a quantum antiferromagnet material.