The Design, Synthesis And Characterization Of Metal-Organic Frameworks Based On Multi-Functional Ligands

Coordination polymer is an important research field of crystal engineering, which can enrich the theory of crystallography and show a wealth of physical and chemical properties as well.ΑBy simply varying the metal ion and/or organic ligands, a variety of coordination polymer materials with unique structural features have been prepared, greatly broadening the structural chemistry of coordination compounds. The MOF materials based on multi-functional ligands containing amide and carboxylate group exhibit interesting physicochemical properties and potential applications in the fields of gas sorption and storage, catalysis, optics, magnetics and electrics.In this thesis, three multi-functional ligands containing amide and carboxylate group are synthesized. Reaction of these ligands with transition metal ions resulted in the formation of a series of ID.2D and 3D coordination polymers under solvothermal conditions or via diffusion method. These compounds have been characterized by means of single crystal X-ray analyses. IR spectra, elemental analyses and thermogravimetric analyses. The main points are addressed:1. Three multi-functional ligands. namely, a C3-symmetric ligand 4,4',4"-[1,3,5-Benzenetriyltris(carbonylimino)]tris-benzoic acid (L1), a C2-symmetric ligand 4,4'-[isophthaloylbis(azanediyl)]dibenzoic acid (L2) and methyl 4-isonicotinamidobenzoate (L3) are synthesized and characterzied by IR spectra, H-NMR etc. Single crystals suitable for X-ray diffraction of LI and L3 are abtained. L1 is found to self-assemble into an interesting core-rosette structure driven by intermolecular hydrogen-bonding interactions. L3 is a 3D network involving hydrogen-bonding andπ-πstacking interaction.2. Reaction of L1 with Zn2+, Co2+ and Cd2+ under solvothermal conditions generated four new coordination polymers having interesting structural motifs: [Zn2(L1)(OH)(H2O)(DMF)]DMF·H2O (1), [Co3(L1)2(DMF)(CH3OH)]xG, (2) [Co1.5(L1)(H20)(DMF)]DMF (3) and [Cd1.5(L1)(H2O)(DMF)]DMF (4). Single-crystal structural analysis revealed that complex 1 exhibits a rare example of two-fold interpenetrating two-dimensional CdI2-type net structure with tetranuclear Zn4(μ3-OH)2(COO)6(H2O)(DMF) serving as secondary building unit (SBU), whereas in 2. theμ3-oxo-tricobalt basic carboxylate SBUs are connected by L3- ligands, leading to a two-fold three-dimensional (6,3)-honeycomb structure. The iso-structural complexes 3 and 4 each has a (4,4)-grid layered architecture in which the SBU is a linear Co3/Cd3 cluster.3. Solvothermal reaction of L2 and Cd2+ afforded one coordination polymer Cd(L2)(H2O) (5). Structural analysis revealed a 3D condensed framework which displayed intense luminescence as a result of the efficient ligand-to-metal charge transfer. On the other hand, the employment of L2 as additive gave rise to the formation of Zn(IN)2 (7) with two-fold interpenetrated 3D metal-organic framework.4. Cryatal engineering of coordination polymers based on 4,5-imidazoledicarboxylic acid and light metal ions K-, Mg2+ resulted in the formation of three simple coordination polymers K(H2idc)(μ-O) (9), K(H2idc)·H2O (10) and Mg(Hidc)(H2O)2·2H2O (11) under solvothemral condition.