Hydrothermal Syntheses And Characterizations Of POM, Cu(I) And Ramifications Of Pyrazine Coordination Polymers

The aim of this dissertation is to use the classical Keggin-POM anions as building blocks to construct new POM-organic hybrids with novel structures. Under the hydrothermal condition, nine new POM-based coordination polymers were obtained based on molecular design. These compounds are described in two chapters.1.In the second chapter, five porous POM-based 3D coordination polymers were synthesized and characterized, namely, {[Cu(2-Mepz)1.5]3(PW₁₂O₄₀)·3H2 O}n (1), {[Cu(2,6-Me2pz)1.5]3(PW₁₂O₄₀)}n (2), {[Cu(2,6-Me2pz)1.5]3(PMo12O40)}n (3), {[Cu3(2,3,5-Me3pz)4](PW₁₂O₄₀)(H2O)}n (4) and {[Cu3(2,3,5-Me3pz)4](PMo12O40)- (H2O)}n (5). (2-Mepz = 2-methylpyrazine; 2,6-Me2pz = 2,6-dimethylpyrazine; 2,3,5-Me3pz = 2,3,5-trimethylpyrazine) A POM-based open metal-organic framework is generated through electrostatic interaction between the POMs and the voids of the 2D metal-organic network. Their structural differences reveal that the steric hindrance of organic ligand plays a key role in modifying the frameworks of POM-based coordination polymers.2.In the third chapter, four new POM-based hybrids with SiW₁₂O₄₀4- as building block were prepared and characterized, namely, [Cu8(2-Mepz)12(SiW₁₂O₄₀)2- (H2O)2]·2H2O (6), [Cu(2,5-Me2pz)]4(SiW₁₂O₄₀)·2H2O (7), [Cu(2,6-Me2pz)]4- (SiW₁₂O₄₀)·4H2O (8) and [Cu(2,3,5-Me3pz)]5(HSiW₁₂O₄₀)(SiW₁₂O₄₀)0.5·3H2O (9). (2-Mepz = 2-methylpyrazine; 2,5-Me2pz = 2,5-dimethylpyrazine; 2,6-Me2pz = 2,6-dimethylpyrazine; 2,3,5-Me3pz = 2,3,5-trimethylpyrazine). A POM-based metal-organic coordination polymer is generated through covalent bonds between the POMs and the 1D metal-organic chains. Investigation of their structural differences indicates that the steric effect of an organic ligand on the structure of POM-based coordination polymer is closely related to the larger volume and the weaker coordination ability of POM anion. Furthermore, a smaller steric hindrance of the organic ligand favors the POM anion functioning as a high-connected linkage in the coordination polymer. We have a conclusion from our work: when SiW12O404- as building block metal-organic units transit from 2D network to 1D chain with the increase of steric hindrance of the organic ligands. While PW12O403- as building block, except compound (1), the result is opposite. So the charge of POM and the steric hindrance of an organic ligand both influence the frameworks of POM-based coordination polymers.Besides the POM hybrids described above, other four new POM-based coordination polymers were also synthesized and their crystallographic data are appended.