Syntheses And Properties Of Coodination Polymers Based On 1,3,5-Tris(1-Imidazolyl)Benzene Ligand

Coordination polymers(CPs) or metal-organic frameworks(MOFs), as a new class of functional material have attracted considerable attention not only because of their fascinating structural architectures and novel topologies but also due to their potential applications in gas storage/separation, optics, magnetism, catalysis, drug release and so on.Many stduies on the construction of functional materials have been carried out, especially the mixed-ligand strategy of the N-donor and multicarboxylate ligands has been widely utilized in this field. Although a great progress has been achieved, it is still a challenge to rational design and synthesis CPs with definite structure and property. Because the structures of coordination polymers can be affected by many factors such as the nature of ligands, coordination geometric need of metal ions, counter anions, ratio of metal ion to ligand, reaction temperature, solvent, pH value etc. Therefore, in order to further understand the self-assembly process, systematic studies on the factors that influence on the structures of coordination polymers are important. Among these, the organic ligand and metal centers play crucial roles in the construction of CPs.In this dissertation, we adopted the mixed-ligand strategy of 1,3,5-tris(1-imidazol) benzene (tib) and auxiliary dicarboxylate ligands with substituents to react with metal salts under solvothermal conditions.26 new coordination polymers were synthesized by rationally controlling the reaction conditions.They are characterized by single crystal X-ray diffraction, elemental analyses, IR, PXRD, and TG analyses. The influence of substituents, metal center, anion, reaction condition and the coordination modes of auxiliary ligands on the structures and properties of the complexes were also investigated. There are four parts in this thesis:1. Six novel coordination polymers were successfully synthesized by introducing 1,4-benzenedicarboxylic acid (p-H2BDC) with different substituent groups p-H2BDC-R (R= NH2, OH, NO2, Br) into Zn(II)-tib system under solvothermal conditions, namely [Zn5(tib)2(p-BDC-NH2)4Gu2-OH)2]·H2O (1), [Zn2(tib)(p-BDC-NH2)SO4(H2O)2]·5H2O (2), [Zn2(tib)2(p-HBDC-OH)2(p-BDC-OH)]·2H2O (3), [Zn(tib)(p-BDC-NO2)]H2O (4), [Zn2(tib)2(p-BDC-Br)]2·2SO4·17H2O (5), [Zn4(tib)2O-BDC-Br)3(H2O)4 SO4]·7.5H2O·2.5DMF (6). Complex 1 is a trinodal (3,4,6)-connected 3-fold interpenetrated 3D framework. Complexes 2-4 were obtained under similar conditions but possess different 2D network structures owing to the substituent effect, all of which generate 3D supramolecular structures linked by hydrogen bonds. Complex 5 is a robust 3D porous framework with 1D channels possessing an unusual (3,4)-connected net, while 6 is a complicated 1D structure with 3D architecture linked by hydrogen bonding interactions. The results show that substituent group, solvent, temperature as well as varied coordination modes of the ligands play important roles in determining the structures of the complexes. Furthermore, the photoluminescence and vapor sorption properties of 1-4, gas sorption and fluorescence sensing properties of 5 and 6 were investigated.2.Eight new metal complexes [Cd(tib)(p-BDC-NH2)]·2H2O (7), [Cd(tib)(p-BDC-OH)]·H2O (8), [Cd(tib)(p-BDC-Br)]·H2O (9), [Co2(tib)2(p-BDC-NH2)(H20)2][p-BDC-NH2]·6H20 (10), [Co(tib)(p-BDC-NO2)(H2O)2] (11), [Co2(tib)2(H2O)6][(p-BDC-Br)2]1.4H2O (12), [Co(tib)2(H2O)2][p-BDC-Br4]·2H2O (13), [Co(tib)(H20)(p-BDC-Cl2)0.5][p-BDC-Cl2]0.5 (14) have been successfully synthesized by solvothermal reactions of Cd(II)/Co(II) salts with tib and p-H2BDC-Rn (R= NH2, OH, NO2, Br, Cl). Complexes 7-9 are isostructural (3,5)-connected 2-nodal 3D frameworks constructed from Cd(II)-tib 3D network and Cd(II)-p-BDC-R 1D helix. In 10, the tib acts as a three connector to link three Co(II) atoms to form a 2D network with single-(6,3)-layer, which is further connected by the p-BDC-NH2 to form a double-layer framework with{63}{66} topology. Both complexes 11 and 13 have 1D chain structures. Complex 11 is a 1D ladder chain, while 13 possess 1D hinged chain. Complex 12 is a typical 4-82 network structure. The auxiliary ligands in 12 and 13 do not take part in the coordination with metal centers and only serve as counteranions to balance the charge. In 14, each tib ligand coordinates to three Co(II) atoms to form a 2D network with single-(6,3)-layers, which are further pillared by p-BDC-Cl2 ligands to generate the final 3D supramolecular (3D anionic) framework. The results confirm that the metal centers, solvents as well as the substituents of organic ligands have subtle but important influence on the structure of the complexes.Meanwhile we investigated the ferroelectric and photoluminescence properties of complexes 7-9 and the vapor sorption properties of 10 and 12.3. Seven novel coordination polymers [Cd(tib)(m-BDC-OH)]·3H2O (15), [Cd(tib)(m-BDC-CH3)]·3H2O (16), [Cd(tib)(m-BDC-CH3)]·11H2O (17), [Co2(tib)2(m-BDC-CH3)2]·2H2O (18),[Co(tib)(m-BDC-CH3)(H2O)]·[Co(tib)(m-BDC-CH3)]·9H2O(19), [Co2(tib)(m-BDC-NH2)2(H2O)]·8H2O (20), [Co(tib)(m-BDC-OH)(H2O)]H2O (21) have been obtanied by solvothermal reactions of tib and 1,3-benzenedicarboxylic acid with substituted R (m-H2BDC-R, R=CH3, OH, NH2) at the 5-positon with Cd(II)/Co(II) salts under different conditions. Complexes 15 and 16 possessing different 3D structures with Cd(II)-tib 2D layers and Cd(II)-m-BDC-R 1D linear chains were botained by tuning the substituents of m-H2BDC-R, and both of them are (3,5)-connected 2-nodal 3D net with the same topology. However, the final structure of 16 is a 2-fold interpenetrating 3D framework. While 17 is a (3,5)-connected 2-nodal 2D network constructed from Cd(Ⅱ)-tib 1D ladder chains and Cd(II)-m-BDC-CH3 1D linear chains. Complexes 18 and 19 were obtained from the same system.18 possess 1D chain structure, while 19 is a 2D network that contains two independent different 2D nets. In 20, the m-BDC-NH2 forms 2D single-layers with the Co(II) atoms, which are further pillared by tib linkers to result in a 2D double-layer framework. Complex 21 is a 1D chain structure. We investigated the photoluminescence properties of complexes 15-17 as well as gas and vapor sorption properties of 20.4. By selecting the tib and 1,4-naphthalenedicarboxylic acid (1,4-H2NDC) to react with corresponding metal ions under solvothermal conditions, five new coordination polymers [Cd(tib)(1,4-NDC)]·2H2O (22), [Cd(tib)(1,4-NDC)]·2H2O (23), [Cd(tib)(1,4-NDC)]-3 H2O(24), [M2(tib)2(1,4-NDC)2]·7H2O [M=Co2+(25) and Ni2+(26)] were obtained. All of these coordination polymers are (3,5)-connected 3D frameworks. Complexes 22-24 are supramolecular isomers with different 3D structures. Complex 22 is constructed from Cd(II)-tib 2D layers and Cd(II)-1,4-NDC 1D zigzag chains, while 23 and 24 have similar 3D structures built from Cd(II)-tib1D ladder chains and simiar Cd(II)-1,4-NDC1D zigzag chains, but their pore sizes and shapes are different, which is mainly ascribed to the solvent effect. Complexes 24-26 are two-fold interpenetrating (3,5)-connected 3D isostructural frameworks. In addition, we investigated the second-order non-linear optical (NLO) effect and ferroelectric property of 22,photoluminescence properties of 22-24 as well as gas sorption properties of 24-26. The results show that 25 and 26 possess the ability to selectively adsorb CO2 over N2, while 24 becomes nonporous after the removal of the free water molecules. The work indicated that the structures and porous properties of the resulting coordination polymers could be modulated by solvents and metal ions.