Magnetic Polymers Based On Sodium Citrate And Organic Phosphonic Acid Ligand: Syntheses And Characterization

Molecular magnetic materials generally refer to the compounds constructed viaself-assembly or controllable assembly, in which paramagnetic metal ions or free radicalscombined with ligands. Molecular magnetic materials include spin-crossover complexes(SCO), pure organic magnetic, pure organometallic single-ion magnetic, single moleculemagnet (SMM), single chain magnetic (SCM), and so on. Single molecule magnet and singlechain magnet exhibit a hysteresis loop at the single molecule level or the single-chain level,respectively. Hence, the investigation of quantum magnets has attracted great attention inpractical applications both of high-density recording media and basic science. Indeed, it stillremains a great challenge in the field of the preparation of molecular magnets with highcritical temperatures and high blocking temperatures. It is also extremely important inunderstanding the relationship between the magnetic and structure.We prepared single crystalline Na4Co(Hcit)2(1)，Na4Ni(Hcit)2(2), in which Sodiumcitrate was employed as a ligand and N,N’-piperazinebis(methylenephosphonate)(H4L) as astructure-directing agent. X-ray crystallography revealed that compounds1and2areisomorphous, and each citrate trianion links10metal ions, which is a novel coordinationmode for the citrate ligand. TGA analyses demonstrated the relative high thermal stability ofthe two compounds. Magnetic analyses showed that complexes1and2are antiferromagnetic.H4L was employed as a ligand reacted with CoCl2, and complexes3and4with spin flopbehavior have been prepared. In3and4the flexible multi-dental ligand H4L acts as a spacerto separate the adjacent metal oxalate magnetic chains. The different magnetic propertybetween3and4can be attributed to the different structural linkage style in3and4, caused bythe variation of the base used in3(sodium) and4(amine).Lastly, two mixed-valance copper complexes CuICuII·At·H3Pdc·H2O (5)(At=3-Amino-1,2,4-triazole，H5Pdc=2,6-Pyridinedicarboxylic acid) and CuI·4CA·H2O (6)(H3CA=cyanuric acid)were constructed under solvothermal and characterized by X-ray singlecrystal diffraction.