The Construction And Studies Of Transition Metal Coordination Compounds Based On Positional Isometric Building Blocks

Currently, design and direct the synthesis of novel metal-oragnic coordination materials with special functions and structures has become leading basic research area in chemistry, physics and material science. Study of these topics affords the important platform to prepare and exploit new materials. Many reported results indicate that the key factor to prepare the desired materials is how to choose and design the suitable molecular building block. Therefore, in this dissertation, based on the literature survey, fully aware of the latest process in triazole-based coordination polymers and combining the actual situation of our group, we choose three groups of eight isomeric organic ligands and isolate thirty-six unreported compounds by different methods such as slow evaporation and hydro(solvo)thermal reaction. Then we tested and characterized the properties of the compounds, such as X-ray single diffraction analysis, powder X-ray diffraction (PXRD), element analysis (EA), infrared spectra (IR), thermo-gravimetric analysis-differential scanning calorimetry, luminescence, absorption and magnetic susceptibility measurements; in addition, we also discussed the different roles of solvent effects, anion effects, metal ions, secondary ligands, reaction temperature and pH value to the structures-properties of the compounds, and summarized some helpful disciplinary conclusions. The major contents of this dissertation as follows:(1) Twenty new coordination polymers of different dimensions have been prepared by using three isomeric organic ligands2/3/4-Hppt (3-(2-pyrazinyl)-5-(2/3/4-pyridyl)-1,2,4-triazole). Single X-ray structural analysis shows that these ligands tend to construct low-dimensional products by coordinating to transitional metal ions because of steric hindrance effects. Among them, compounds1-9,10-15and17are OD discrete structures. Compound20shows1D chain. Compound10,18and19presents2D layers with (4,4) topology. Compounds16shows a3D NbO network, and further there still remains ID channels with no solvent filled after two-fold interpenetrating. During the synthesis progress,2/3/4-ppt exhibits different coordination modes tuned by the isomeric effect, solvent effects, metal ions, and anion effects. Also, the thermal stabilities of1-4,6-13,16,18and20, the fluorescent properties of7,18and20, the absorption and magnetic properties of16were carried out and discussed, respectively. (2) To increase the dimensions of the compounds based on2/3/4-Hppt liangds, we introduce the secondary ligands such as rigid-carboxylic acids and successfully prepared five compounds. Among them, compounds21,22and25show the2D layers. Compounds23and24present3D networks. The thermal, fluorescent and magnetic properties of them were carried out and discussed, respectively.(3) To rationally construct the high-dimensional products, we design and choose the other three isomeric ligands2/3/4-Hptt (3-(2/3/4-pyridyl)-5-(3-triazolyl)-1,2,4-triazole) which poss more monodentate and bidentate chelating sites. Four compounds have been isolated based on the2-Hppt ligand. Among them, compounds26and27are supramolecular isomerisms which were isolated by using different solvents. Also, the transformations, thermal stabilities and magnetic properties were compared and discussed carefully. The thermal stabilities and luminescence of28which is the isomorphism of the26were also tested and analyzed. In addition, compound29and another different color compound were prepared under the same experimental system at different reaction temperature.(4) As an extension work of our group, we have reported here seven compounds based on two isomeric ligands2-amino-5-(3/4-hydroxybenzoate) pyridine. In these compounds,30,32and34display the similar2D layer with different chiral helical chains, single chiral helical chains and (6,3) topology, respectively. Compound31,35and36show ID double helical chain, ID double chain and ID ladder-like chain, respectively. Compound33presents pcu topology by considering the Cd2cluster as a node. The luminescent properties of compound32and33have been characterized.In summary, we have focused on the research of the positional isomeric ligands in the context of crystal engineering. On the other hand, we have also studied the relationship between supramolecular structures and properties, and further studied their potential applications such as optical, magnetic and adsorption materials. The thesis not only provides important information for the synthesis and property of triazole-based coordination polymers, but also affords a new idea and method to design and prepare functional compounds.