Metal-organic Framework Constructed From Flexible Ligand: Design、Synthesis And Properties

As an emerging research area, metal-organic frameworks (MOFs) have attractedconsiderable attention in recent years because of their large potential applications in gas storage,ion-exchange, luminescence, catalysis, magnetism and electrochemistry. Metal coordinationpolymers based on carboxylic acid ligand are prevalent because of their high structural stabilityand various coordination modes. Amide decorated aromatic carboxylate ligands can increase theflexibility of the ligand, and also generate a large inner cavity. In this research, we designed andsynthesized a series of amide decorated aromatic carboxylate ligands, and we obtained15novelMOFs through the assesibly reaction between the synthesized ligands and transition metals andrare-earth metals. All complexes have been characterized by single-crystal X-ray diffractionanalyses, thermogravimetric analyses, powder X-ray diffraction (PXRD), fluorescencemeasurement, magnetic measurement and gas absorption. These results were briefly described asfollows:1、Two d10polymers based on amide decorated aromatic carboxylate ligands, namely,[Cd2L(1)(DMA)2(H2O)](DMA)3(1) and [ZnL(2)](DMA)(C2H8N)2(H2O)3(2) were synthesizedunder hydrothermal condition. We have analysised the crystal structure and studied theluminescence and gas absorption properties. Compound1is a (4,4)-connected3D frameworkwith a1-D channels along crystallographic a-axis. Compound2is a (4,4)-connected dia or(3,4)-connected tfa topological2-fold interpenetrating3D coordination network. Thefluorescence emissions spectrum of complex1tentatively assigned to the ligand-to-metal chargetransfer (LMCT) and complex2tentatively assigned to the intraligand charge transfer.Compound2exhibited a good adsorption properties.2、We designed and synthesized four amide decorated N-containing carboxylic acids ligandsH2L(3)、H2L(4)、H2L(5)、H2L(6), and coordinated with Cd(Ⅱ)、Co(Ⅱ)、Zn(Ⅱ)、Cu(Ⅱ)、Ce(Ⅲ) ions to construct six coordination polymers:[CoL(3)(pyr)2](H2O)3(DMA)(3),[CeL(3)(NO3)(H2O)](DMA)3(4),[CuL(4)(DMA)](DMA)(5),[CdL(4)(DMA)(H2O)](6), [CoL(5)(pyr)2](DMA)(H2O)(7),[ZnL(6)(C2H6N)(H2O)](DMA)6(8). Compound3is acoordination polymer with one dimensional double strand chain, which further formstwo-dimensional architecture through π-π stacking interaction. Compound4exhibits1D Cechain, linking H2L(3) to form two-dimensional plane structure, and thus are extended into a3-Darchitecture through π-π stacking interaction. Compound5exhibits helical structure andcompound6displays a dinuclear structure-shuttle unit. Compound7has the same configurationcompared with compound3, compound8exhibits a rhombus structure, which further formstwo-dimensional architecture through hydrogen bonds and π-π stacking interaction. Moreover,the fluorescent properties of complexes4,6,8, magnetic properties of complexes3,7and gasabsorption properties of complexes3,4,5have been investigated.3、We designed and synthesized three amide decorated nitro-substitution carboxylic acidsligands H2L(7)、H2L(8)、H2L(9), and coordinated with Cd(Ⅱ)、Co(Ⅱ)、Zn(Ⅱ) ions to constructseven coordination polymers:[ZnL(7)(H2O)2](H2O)(9),[CdL(7)(bimb)0.5(H2O)](H2O)(10),[CoL(7)(pyr)2](CH3OH)(H2O)2(11),[CoL(7)(bimb)](H2O)2(12),[Co2L(8)2(bimb)(H2O)8](13),[CoL(9)2(bimb)](H2O)4(14),[ZnL(9)2(bimb)](H2O)5(15)(bimb=1,4-bis(1-imidazolyl) benzene).Compound9,10,11and12based on the same ligand [H2L(7)] were constructed. Compound9exhibits a dinuclear1D chain, and forms a3D architecture through π-π interactions andhydrogen bonds. Compound10is a mixed-ligand coordination polymer based on H2L(7) andbimb, and exhibits similar dinuclear1D chain compared with compound9. Bimb ligands act asbidentate bridging connectors to link1D chains. Compound11and12adopt different auxiliaryligand pyridine and bimb. Both exhibit a dinuclear1D chain, which further forms a3Dsupramolecular architecture via inter-chain π-π interactions. Compound13exhibits S-type unit,and forms a3D architecture with hydrogen bonds. Compound14and15are isostructures andeach displays an one-dimensional (1D) zigzag chain, which further forms a3D supramoleculararchitecture with1-D channels via inter-chain π-π interactions and hydrogen bonds. Moreover,the fluorescent properties of complexes9,10,15, magnetic properties of complexes11,12,13have been investigated.