Structure And Magnetic Properties Of 3d Metal Ions Coordination Polymers Constructed With Polycarboxylic Acids And Positional Isomeric Ligands

The investigation of molecule-based magnetic materials with novel structure has become a fascinating subject in the fields of material and coordination chemistry for their interesting properties and potential application. Generally, two approaches, ferro-and ferrimagnetic (FO and FI), can lead to spontaneous magnetization. In the FI systems, the weak-ferromagnets due to spin canting also have spontaneous magnetization and are efficient to construct molecular magnets. Focused on the top topic, fourty-six 3d metal ions coordination polymers constructed with polycarboxylic acids and bent positional isomeric ligands have been hydrothermally synthesized. The structures of these complexes have been determined by X-ray crystallographic methods and characterized by element analyses and IR spectra. Their magnetic and fluorescent properties have been studied.The main contributions in this work are below:1. We have synthesized 26 Co(II) complexes with polycarboxylate ligands and positional isomeric dipyridyl bridging ligands. The magnetic property studies indicate that there are 11 Co(II) complexes showing interesting phenomenon of spin-canting. 1) Complexes 1,8 and 13, exhibit the coexistence of spin-canted weak ferromagnetism and long-range magnetic ordering, with TN= 10 K,10 K,9 K, respectively; 2) Complexes 6-9, with the similar structural characteristic, exhibit the phenomenon of spin-canting. The canting in these complexes may be caused by the acentrosymmetric syn-anti carboxylato bridge, which together with the anisotropy of the Co(II) ions. However, from the point of the structural-magnetic relation, the canting in 8 can be observed more easily, which suggests that the different orientations of the pyridyl groups in bpt isomers can affect the magnetic properties of the final complexes, and play a crucial role in the complicated system for the investigation of spin canting as a function of various subtle structural factors; 3) Complexes 3-5, with similar structural characteristic but different guest molecules, exhibit interesting magnetic phenomenon:solvatostructural effect; solvatomagnetic effect;field-induced spin-flop phenomenon and uncompensated AF alignment. 2. We have synthesized 7 Ni(II) complexes with polycarboxylate ligands and positional isomeric dipyridyl bridging ligands. The magnetic property studies indicate that there are two Ni(II) complexes showing interesting phenomenon of spin-canting. Compound 24 having a 3D "brick-wall"-like architecture, exhibits canted antiferromagnetism at 5.0 K. Below this temperature, slow relaxation is observed from the ac susceptibility measurements corresponding to the spin-glass like behavior.3. We have synthesized 10 Zn(Ⅱ);and 3 Cu(Ⅱ) complexes with polycarboxylate ligands and positional isomeric dipyridyl bridging ligands. This paper may be a new and interesting example to systematically investigate the influence of the positional isomeric ligands on the structures and properties of their complexes, and to explore the net relation graph (NRG) properties, which are very useful in supra-molecular chemistry, crystal engineering and design.