Synthesis, Structure And Properties Of Transitional / Rare Earth Complexes Based On Pyridine Carboxylic Acid Amphoteric Ion Ligands

As a new kind of inorganic-organic hybrid materials, Metal-organic frameworks (MOFs) has become one of the frontiers in chemical research because of their rich variety of frameworks and the interesting physical and chemical properties in the last few years. In order to obtain the MOFs that have special structure and function, it is more and more dependent on the design of organic ligands that have specific structure and special functional components. Due to the easy modification of the backbones and the intriguing electronic transfer properties, in this paper, pyridinium zwitterionic compounds as organic ligand skeleton structure, carboxylic groups as coordination sites were introduced to the skeleton of pyridinium by structural modification, five pyridinium zwitterionic polycarboxylic ligands were designed and synthesized. Twelve novel coordination polymers were successfully synthesized by the self-assembly between pyridinium zwitterionic polycarboxylic ligands and transition/rare earth metal ions at room temperature. Based on their crystal structures, the application properties of some complexes were studied. The main research work of this paper is as follows:1. As coordination sites, carboxylic groups were introduced the skeleton of pyridinium by structural modification, five pyridinium zwitterionic polycarboxylic ligands were designed and synthesized. The structures of these ligands were characterized by IR and NMR. The configuration of some ligands was determined by X-single crystal diffraction. More over, the solid-state fluorescent of all ligands were measured, and the electronic transfer properties of all ligands were characterized by UV spectrum.2. Based on transition metal ions and pyridinium zwitterionic polycarboxylic ligands, nine novel complexes were successfully synthesized by controlling the pH value, metal ions, anions and other synthesis conditions at room temperature. Complexes 1-3 are mononuclear structure, complex 4-7 are allomerism three nuclear zero dimensional structure, Complex 1 displays a 1D double-chain framework containing the linear array of trinuclear [Mn3] unit. For complex 2, the distorted chair-like [Cu4 (μ3-O)2(H2O)6]6+clusters cores are linked by L1 to generate a 1D double-chain framework. Based on the structure features, the complexes 4-9 solid-state luminescence properties were characterized, fluorescence spectra analysis suggested that the potential field around L1 ligand should be an important factor on the fluorescent emissions. Magnetic measurements indicate that antiferromagnetic interactions exist within compound 8 and 9. Ion exchange properties of complexes 8 and 9 that have a lot of free the perchlorate ion were studied.The results show that the free perchlorate ions cannot exchange by other ions in the complexes 8 and 9. The oxidation properties of Cu(II) complex 4 and 9 were characterized by cyclic voltammetry (CV). The results indicate that the oxidation ability of complex 4 was stronger than complex 9. The complexes 4 and 9 were used as heterogeneous catalysts for the catalytic oxidation of 2,6-two (DMP). The complexes 4 and 9 demonstrate remarkable capability for the catalytic oxidation of 2,6-dimethylphenol (DMP) generated benzoquinone (DPQ) with high selectivity, the catalytic oxidation of complexes 4 is stronger than the complexes 9, the catalytic cycle of complexes 4 and 9 were studied, the complexes 4 and 9 appeared obvious catalyst poisoning phenomenon.3. Three 3D complexes 10-12 with microporous structure were successfully constructed by the self-assembly between pyridinium zwitterionic polycarboxylic ligands and rare earth metal ions at room temperature, and the complexes 4-9 solid-state luminescence properties were characterized, the Eu complexes 10 and Tb complexes 12 emitted intense light was readily observed with the naked eye at room temperature. Compared with the solid fluorescence of the ligands, quenching of the solid fluorescence occurred in Gd complexes 11. The small molecule recognition and ion recognition of Eu complexes 10 and Tb complexes 12 were studied, and the luminescence of the Eu complexes 10 and Tb complexes 12 displays highly selective sensing of the Fe3+ ion and nitrobenzene. The temperature-sensitive luminescent properties of Eu complexes 10 and Tb complexes 12 were studied. With the change of temperature, the solid fluorescence intensity and color of Eu complexes 10 and Tb complexes 12 was changed, it indicate that the Eu complexes 10 and Tb complexes 12 have potential application value as luminescent thermal sensing material.