Studies On Crystal Structures And Functions Of Metal-Organic Coordination Polymers Constructed From Novel Thiophene-based Ligands

Metal-organic coordination polymers (MOCP) have attracted considerable attentions not only because of their various interesting architectures, but also of their wide potential applications in material science, such as photoluminescence, magnetism, gas adsorption, catalysis, templating metal nanoparticles and so on. However, the research on metal-organic coordination polymers constructed from thiophene-based organic ligands is rather limited and needs more efforts and concentrations. Therefore, we design and synthesize a series of novel thiophene-based dicarboxylate linkers. And 22 metal-organic coordination polymers were rational designed and synthesized. Further study of their crystal structures and physical properties revealed that there was clear influence between the above two aspects.This dissertation includes the following three parts: (1) the brief introduction about the crystal structures and their physical properties; (2) metal-organic coordination polymers built from H2DBTA; and (3) metal-organic coordination polymers constructed of H2DTTA.1. Metal-organic coordination polymers built from H2DBTA(a) Through the solvothermal reaction of H2DBTA and Mn(ClO4)2, a 3D porous MOCP (1) was obtained, in which the dinuclear Mn2-SBU performed unusual magnetism in the temperature range of 220 K to 240 K. Correspondingly, the crystal data of the MOCP under different temperatures suggested that the compound exhibited unusual crystal structural variation as well, which possibly could be ascribed to negative thermal expansion. The results supported that there were important relationship between the structure and magnetic behavior in metal-organic coordination polymers.(b) The rational design and syntheses of nine Zn-DBTA MOCPs (2-10) were carried out after the careful analysis of the structural characteristics and common coordination fashions of secondary N-donor linkers. These MOCPs showed various structural types, such as 1D chains, 2D layers and 3D frameworks. Furthermore, the DBTA ligand functionalized as a flexible dicarboxlate linker with various coordination modes. The good photoluminescences and comparatively long radiative lifetimes help them become a family of promising fluorescent materials.(c) Four metal-DBTA coordination polymers (11-14) constructed of Cd2+, Co2+ and Ni2+ centers expanded the crystal structure types and metal types. The DBTA ligand performed two additional coordination modes which again supported its wonderful coordination flexibility.2. Metal-organic coordination polymers constructed of H2DTTA(a) The 2D two-fold interpenetration MOCP (15) made of DTTA and Ni2+ was taken as a good artificial template to support silver nanoparticles. The resulted Ag(0)/15 showed good catalytic activity and recycle ability in the catalysis of the A3 reaction of aldehyde, secondary amine with alkyne. Furthermore, the catalyst exhibited good selectivity towards linear aliphatic aldehydes rather than aromatic and branch aliphatic aldehydes, which possibly owing to the fitness between the shapes and sizes of the reaction substrates to the supported environments in/on the MOCP 15.(b) We have successfully prepared three related Mn2+ MOCPs (16-18) through solvothermal reactions of the same reagents, H2DTTA and Mn(ClO4)2, just by adjusting the reaction solvents and co-ligands. The comparative study of their crystal structures and photoluminescence reveals that solvents and co-ligands in each preparation of the MOCP have significant influence on the crystal packing mode and intramolecular electron distributions, which provides a promising method to regulate the physical properties of MOCPs by controlling the preparation process. Furthermore, the strong emission, near-visible or visible excitation wavelengths and comparatively long radiative lifetimes of their photoluminescence make the three MOCPs promising candidates for fluorescent materials.(c) Four Lanthanoid-DTTA coordination polymers (19-22) with large 1D nanotubes showed good photoluminescence and catalytic activity in the reaction of aldehyde with alcohol. There was good selectivity towards the sizes and shapes of the aldehyde substrates as well.