Studies On The Construction And Properties Of Magnetic Coordination Polymers Based On Azido Ligand

In the past two decades, the design and synthesis of magnetic coordinationpolymers with peculiar structure and potential application have become a focus ofintense research activities in the fields of coordination and material chemistry. Thekey to design such materials is to select a bridging ligand that can effectively mediatethe magnetic coupling and construct novel structures. As a bridging ligand, the azidoanion which displays multiple bridging modes and magnetic exchange pathwaysbetween metal ions has been well used in the preparation of molecular magneticmaterials. The coligands and synthesis condition are the primary factors indetermining the structures of the complexes. However, it is still hard to exactlyforecast which coordination mode azido ligand will be adopted to coordinate thetransition-metal center in a detailed system.In our efforts to construct new molecule-based magnetic materials andinvestigate the magneto-structural correlations, in this dissertation, a series of newmagnetic complexes have been successfully obtained by the selection of azide asbridging ligand and N-heterocyclic carboxylic acid, di(1H-imidazol-1-yl)methane andthe rigid aromatic dicarboxylate-like as coligands under solvothermal condition. Thecrystal structures, topological analysis and magnetic properties of these complexeshave also been investigated. The nature of the properties of coligands, the reactionratio of azido and the metal ions with different anions factors are the greatly influenceon the structures of the complexes. The main points are summarized as follows:1. Metal-azido complexes with pyridyl or pyrazinyl acid as coligands(1). Eight azido-MnIIcomplexes with pyridyl or pyrazinyl acid as coligands havebeen synthesized and structurally characterized. Due to the high reaction ratio ofazido, the complexes always show the two-dimensional (2D) or3D structures. Theinvestigaton of magnetic properties of complexes1-3demonstrates that dominantantiferromagnetic coupling existing in azido-MnIIcomplexes, but duo to thecoligands, the complexes show various magnetic properties. (2). With the combination of azido and CoIIwhich has strong single ionanisotropy, nine azido-CoIIcomplexes with pyridyl or pyrazinyl acid as coligandshave been synthesized and structurally characterized. All the nine complexes are the3D structures with [Co2],[Co3] or [Co4] as the building blocks. The investigaton ofmagnetic properties of complexes9-10demonstrates that ferromagnetic couplingintra-[Co4]-cluster and antiferromagnetic interaction inter-[Co4]-cluster exists incomplex9, while complex10exhibits metamagnetism with a critical field of5.5kOe.2. Metal-azido complexes with di(1H-imidazol-1-yl)methane as coligands(1). Eight metal-azido complexes with di(1H-imidazol-1-yl)methane as coligandhave been synthesized and structurally characterized. The reaction ratio of azido andthe metal ions with different anions factors were found to greatly influence on thestructures of the complexes.(2). Using the methord of “coordinated group” division, seven metal-azidocomplexes with di(1H-imidazol-1-yl)methane and the rigid aromaticdicarboxylate-like as coligands have been synthesized and structurally characterized.All the seven complexes are the3D structures with [M2],[M3] or [M4] as thebuilding blocks. The investigaton of magnetic properties of complexes26-28demonstrates that they all display ferromagnetic coupling between CoIIions butantiferromagnetic interaction between [Co3] or [Co2] units.