Syntheses And Properties Of Novel Coordination Polymers Based On The Tetrahedral Carboxylic Acid Ligand

Recently, coordination polymers or metal-organic frameworks (MOFs) have drawn great attention because of their potential applications in adsorbents,photoluminescence,magnetism,catalysis,light-harvesters,chemical sensors and devices. In the construction of coordination polymer materials, the multidentate organic ligands maintain the structural integrity and configuration throughout the assembly process in most cases. It is a effective strategy of constructing coordination polymer by using specific structure and functions of the organic ligand. In this thesis,based on the principle of crystal engineering, we focus our study on the design of ligands with specified geometry and the construction of fluorescent MOFs with interesting structures and multifunctional properties. In order to construct coordination polymer with porosity, we use both semi-rigid and rigid tetrahedral organic carboxylic acids as ligands. As results, 18 metal-organic coordination polymers were synthesized successfully, and their structure and properties were studied in details.This dissertation consists of five chapters.Chapter 1,Introduction. We gave a brief introduction to the research background and classification of coordination polymers. Meanwhile, a brief description of our research strategies and results of this thesis were given.Chapter 2, Coordiantion polymers built on the semi-rigid octadentate carboxylic acid ligand. By using an octadentate carboxylic acid ligand,tetrakis[(3,5-dicarboxyphenoxy)methyl] methane, four novel coordination polymers[Cu4L(H2O)4]·31H2O (1), [Zn4L(H2O)4]·DMF·6H2O (2),[In2L][NH2(CH3)2]2·(DMF)4(H2O)16 (3)和[Mg3L][NH2(CH3)2]2·(H2O)5 (4) have successfully synthesized.Compounds 1 and 2 are isostructural, and possess a(4,8)-connected scu net with the voids filled with coordinated and disordered water molecules. Compound 3 is a (4,8)-connected net with scu topology and exhibited permanent porosity. Compound 4 possesses a 4-connected 3D framework with nbo topology, which was built upon a 4-connecting Mg3 cluster and a 4-connecting L8-ligand. In addition, compounds 3 and 4 exhibited strong fluorescent emissions upon excitation at room temperature. The fluorescence sensing experiments showed that fluorescence intensities of compound 3 changed with the different polarity of solvent.Further experiments showed that compound 3 exhibited a selective, efficient emission quenching response towards nitroaromatic explosives. These results indicate that compound 3 are potentially sensor materials for nitroaromatic explosives. The syntheses of compounds 1-4 imply the use of semi-rigid octadentate carboxylic acid ligand promises the successful synthesis of the open 3D framework.Chapter 3, Coordiantion polymers built on the rigid octadentate carboxylic acid ligand. By using a rigid octadentate carboxylic acid ligand 5,5’,5,",5’"-silanetetrayltetraisophthalic acid (H8L), five novel coordination polymers[Cu4L(H20)4]·2DMF·10H2O (5), [Zn5L2(H20)4][NH2(CH3)2]6·2DMF·4H20 (6),[Cd3(H2L)2][NH2(CH3)2]6·4DMF·14H2O(7),[Cu4(HL)(bipy)(OH)H20)]·4H20 (8)and [(Zn4O)L(H3O)2]·2H2O (9)have successfully synthesized. The structure, thermal stability, gas absorption and fluorescence properties of five compounds were studied.Compound 5 is a (4,8)-connected net with scu topology. The framework of 6 and 7 are intricate, which can be simplified 4-nodal (4,4,4,8)-connected network and 3-nodal (4,4,6)-connected network, respectively. Compound 8 is a complicated framework built on two different Cu4 clusters, between two Cu4 clusters through a carboxyl COO to form an infinite chain. Compound 9 is a uninodal 4-c net with Isz topology. Compound 5 exhibits permanent porosity, thus the adsorption properties has been characterized. Compounds 6,7 and 9 exhibited strong fluorescent emissions upon excitation at room temperature. The results show that the rigid octadentate carboxylic acid ligand provides a feasible method for building a specific structure of coordination polymer and can successfully lead to coordination polymer with high node topology due to its flexible ligand configurations.Chapter 4, Coordiantion polymers built on the tetrahedral carboxylic acid ligands. By using three rigid tetrapodal linkers tetrakis(4-carboxyphenyl)silicon(H4L-4),tetrakis(3-carboxyphenyl)silicon (H4L-3) and semirigid tetrahedral alkoxyl carboxylate ligand (H4L), nine coordination polymers 10-18 have successfully synthesized. Five compounds,formulated as [NdL(H2O)][NH2(CH3)2] 2DMF-4H2O(10), [Eu4L3(H2O)6]·4DMF·2H20 (11), [Er4L3(H2O)6]·2DMF·5H20 (12), [CoL][NH2(CH3)2]2·2.25H2O (13),[Co3L2][H3O]2·6DMA (14),have been prepared via solvothermal synthesis based on rigid tetrahedral ligand tetrakis(4-carboxyphenyl)silicon (H4L-4). Two coordination polymers, formulated as[Zn2L(H20)] 2DMF·2.5H20 (15),[CdL][NH2(CH3)2]2·2DMF·H20 (16),have been prepared via solvothermal synthesis based on rigid tetrahedral ligand tetrakis(3-carboxyphenyl)silicon (H4L-3). Two coordination polymers, formulated as [Co2L(DPE)]·(guest) (17) and [Cd2L(C3N2H3)(H2O)]·(guest) (18),have been prepared via solvothermal synthesis based on semirigid tetrahedral alkoxyl carboxylate ligand (H4L). Compound 10 is a rare (4,8)-connected net with flu topology. Compounds 11 and 12 are isostructural,which is built on a 12-connecting S-shape {M4(COOR)12} cluster (M = Eu,Er) and a 4-connecting L4- ligand.Compounds 13 and 15 are uninodal 4-connected net with sra topology. Compound 14 is a (4,8)-connected net with alb topology. Compound 16 is a bimodal(4,4)-connected network built on a 4-connecting Cd center and a 4-connecting L4-ligand. Compound 17 is a (4,4)-connected PtS net with the voids filled with coordinated DPE and disordered solvent DMF and water molecules. Compound 18 possesses a (4,6)-connected 3D framework with toc topology built upon a 6-connecting Cd3 cluster and a 4-connecting L4- ligand. Compound 10 possesses permanent porosity as confirmed by N2,H2,O2,CO2 and CH4 gas adsorption measurements. Compounds 15 and 16 exhibited strong fluorescent emissions upon excitation at room temperature. From a topology point of view,H4L-4, H4L-3 and H4L ligands in nine compounds can be regarded as 4-connected node. However, it adopts flexible coordination modes to meet various requirements of different metals, thus forming a wealth of topology network.Chapter5, Conclusions. A brief conclusion on this thesis and an outlook for our future work were given.