Syntheses, Structures And Properties Of Organic Carboxylate Coordination Compounds

This dissertation consists of three parts:Firstly, we used rigid ligands biphenyl-3,4’,5-tricarboxylic acid and 4,4"-Dicarboxyl-(1,1’,3’,1")-Terphenyl, and synthesized five coodination compounds with novel structures and properties by hydrothermal method and liquid diffusion method, respectively. Secondly, we synthesized eight coordination compounds with novel structures and properties by assemble of flexible ligands 2,2’-(naphthalene-2,7-diylbis(oxy)) diacetic acid and 2,2’-(biphenyl-4,4’-diylbis(oxy))diacetic acid. Thirdly, we got nine new coordination compounds with novel structures and properties by using semi-rigid ligand 4,4’-(hexafluoroisopropylidene)bis(benzoic acid) and N-donor ancillary ligands to assemble with metal ions.1. Syntheses, Structures, and Properties of Rigid Carboxylic Acid-Based Coordination Compounds1.1. Syntheses, Structures, Photoluminescence and Magnetic Properties of Biphenyl-3,4’,5-tricarboxylic Acid Coordination Compounds.Solvothermal reactions of biphenyl-3,4’,5-tricarboxylate with transition metals, in the presence or absence of auxiliary ligands, produced four new coordination compounds, namely,{[Cd3(L)2(H2O)9]·(H2O)5}n (1), {[Cd2(HL)2(timp)(H2O)4]·(H2O)4}n (2),{Mn(HL)(bipy)0.5(H2O)}n (3), {Co(HL)(bipy)0.5(H2O)}n (4). The carboxylic acid ligand in compound 1 is T-shaped, which can induce the generation of two dimensional (2D) T-shaped molecular bilayer motifs. These 2D motifs give rise to three dimensional (3D) supramolecular frameworks with rectangle channels by polycatenating with each other to give rise to the 3D supramolecular framework with rectangle channels. Compound 2 got its 3D supramolecular network by the π-π interactions between one dimensional (1D) ladders. And 2 exhibits strong emission due to the π-π conjugation between carboxylic acid ligands. Single-crystal X-ray diffraction analyses reveal that 3 and 4 are beautifully nisomorphous and isostructural. They both crystallize in the triclinic PI space group. Although compounds 3 and 4 are isostructural, the magnetic properties of 4 are very different from that of 3 because of the orbital contribution of CoⅡ ions. Compound 3 shows an antiferromagnetic coupling, but the ferromagnetic coupling between CoⅡ ions dominates the magnetic properties of 4.1.2. Syntheses, Structures, Photoluminescence and Magnetic Properties of 4,4"-Dicarboxyl-(1,1’,3’,1")-Terphenyl Coordination Compounds.Reaction of uranium oxynitrate hexahydrate with 4, 4"-dicarboxyl-(1,1’,3’,1")-terphenyl (H2L) by liquid diffusion method resulted in a coordination compound{[UO2(L)(DMF)]·H2O}n (5). The uranyl unit keeps the shape of nearly a straight line in compound 5. The carboxylic acid ligands act as bidentate bridging ligands to connect uranium ions into 1D chain which contains 8-membered rings and 32-membered rings ranged alternatively. Adjacent chains connect by π-π interactions between the ligands to form 2D layer. Compound 5 showed spectrum consisted of absorption components in the UV and visible region, which is typical of uranyl compounds.2. Syntheses, Structures, and Properties of Flexible Carboxylic Acid-Based Coordination CompoundsEight new coordination compounds, namely [ZnL1(H2O)2]]n(6), [CdL1(H2O)2]n(7), [CoL1(H20)3]n(8), [EuL1(NO2)(H2O)]n(9), [SmL1(NO2)(H2O)]n (10), [CdL2(H2O)]n (11), [CoL2(H2O)4]n (12), [NiL2(H2O)4]n (13)were synthesized under solvothermal conditions based on flexible ligands 2,2’-(naphthalene-2,7-diylbis(oxy)) diacetic acid (H2L1) and 2,2’-(biphenyl-4,4’-diylbis(oxy))diacetic acid (H2L2). The two flexible ligands exhibited complicated coordination modes due to the flexibility of-OCH2COO-group. Compounds 6 and 7 both exhibited 3D supramolecular structures formed by 1D chains through intermolecular interactions. Due to the different torsion angles of flexible arms, the π-π stacking interactions exist in compound 7 with hydrogen bonds together to give rise to the 3D network, whereas in compound 6 only hydrogen bonded interactions join adjacent 1D chains. There are two distinct crystallographically independent cobalt atoms (Col and Co2) in compound 8, Co2 atoms are linked by carboxyl bridges to generate 1D chains, and all cobalt atoms are bridged by L12- ligands to form a 2D layer. The large quantities of coordinated water give plentiful hydrogen bonds, the 2D layers are connected by hydrogen bonds to give rise to a 3D structure. Compounds 9 and 10 all crystallize in the monoclinic crystal system, space group are P2(1)/c and exhibit similar structures. There are two types of channels in the structures, which are arranged in "-A-B-A-B-" model. The oxygen atoms of -OCH2- groups did not coordinate to metals in compounds 6-10, which may due to the big steric hindrance of naphthalin rings. While in compound 11, the three oxygen atoms in-OCH2COO-group coordinated to metals together, for the steric hindrance effect of biphenyl rings is weak compared with naphthalin rings of L12- ligand. Compound 11 represents pcu a-Po topology by using flexible L22" ligands as linkers. Compounds 12 and 13 crystallize in the triclinic space group P1 and form 3D supramolecular structures by hydrogen-bonded and π-π stacking interactions. The emission spectra of free ligand H2L1, compounds 6,7 and 9 in the solid state at room temperature are investigated upon the same excitation.6 shows a small blue shift compared with that of the H2L1 ligand, while 7 exhibits the similar emission character to the free H2L1 ligand. The decreased intensity of 6 and 7 are perhaps caused by amounts of coordinated water. The spectrum of compound 9 exhibits the characteristic transitions of Eu(III) ions. The absence of the ligand-based emission suggests that the energy transfer from the ligand to the Eu(III) center is effective (LMCT). The luminescent properties of free ligand H2L2 and compound 11 are also investigated.11 shows similar emission character to the free H2L2 ligand with a small blue shift. In addition, weak antiferromagnetic exchange interactions are observed in 8, 9,12 and 13.3. Syntheses, Structures, and Properties of Semi-rigid Carboxylic Acid-Based Coordination Compounds3.1. Syntheses, Structures, Photoluminescence and Magnetic Properties of Coordination Compounds Assemblied by4,4’-(hexafluoroisopropylidene)bis(benzoic acid) and Trasition Metals.Four new coordination compounds, namely{[Cd3(L)2(μ3-OH)2(H2O)]·H2O}n (14), {Ni(L)(bipy)}n (15),{Cu3(L)2(bipy)(μ2-OH)2(DMF)2}n (16) and{Co2L2(H2L)(H2O)}n (17), have been synthesized by the solvo thermal reaction of 4,4’-(hexafluoroisopropylidene)bis(benzoic acid) (H2L) with different transition metal ions in the presence of co-ligand 4,4’-bipyridine (bipy). Compound 14 displays a 3D framework containing infinite bands constructed of heptanuclear cadmium clusters. The carboxylic acids adopt three coordination modes in structure. In compound 15, [Ni2C2O4] secondary building units (SBUs) are linked by acid ligands into a 1D ribbon, which are further assembled into a 2D non-interpenetrated structure with {44.62} topology. Compound 16 displays a 3D porous framework. With the topological viewpoint, the Cu(Ⅱ) centers can be viewed as 8-connecting nodes, and all crystallographically independent acid ligands act as 3-connecting nodes, the whole structure can be represented as a new{43}2{46.614.88} net. Compound 17 exhibit 3D open framework containing paddle-wheel units. By regarding paddle-wheel unit as a six-connected node, the multidimensional structures can be simplified to a duplicate interpenetrated{412.63} net topology. The magnetic investigation of 16 show that in the higher temperature range above 14 K, the magnetic properties are dominated by ferromagnetic interactions, and below 14 K the magnetic properties are dominated by the effect of antiferromagnetic interactions and/or zero-field splitting.14 showed a broad, weak violet photoluminescence in the solid state.3.2. Syntheses, Structures and Photoluminescence Properties of Coordination Compounds Assemblied by 4,4’-(hexafluoroisopropylidene)bis(benzoic acid) and Different Imidazole Ancillary Ligands with Zn(Ⅱ) and Cd(Ⅱ)Five new compounds, namely{[Zn(L)(L1)]·(H2O)(DMF)2}n (18),{Cd(L)(L1)0.5}n (19),[Zn2(L)2(L2)2]·DMF}n (20),{[Zn(L)(L3)]·(H2O)5}n (21) and {[Cd2(L)2(L3)1.5(H2O)]·2H2O}n (22), have been synthesized by the solvothermal reaction of 4,4’-(hexafluoroisopropylidene)bis(benzoic acid) (H2L) with Zn(Ⅱ) and Cd(II) in the presence of ancillary ligands 1,4-Bis(imidazol-1-ylmethyl)benzene (L1), 4,4’-bis(imidazol-1-ylmethyl)-biphenyl (L2), and 4,4’-bis(benzimidazol-1-ylmethyl)biphenyl (L3). Compound 18 display a 3D supramolecular structure formed by the π-π interactions between neighboring L1 ligands. Imidazole rings and phenyl rings are both have contributions to π-π interactions. All Cd atoms in compound 19 are connected to form a 1D chain by oxygen bridges and carboxyl bridges, alternately. Then the L1 ligands of trans-configuration joined all infinite 1D chains into a 2D layer. The 3D framework of 19 is finally obtained by linking 2D layers through acid ligands. The whole structure can be represented as a {422.53.63} net. Because left-handed and right-handed helical chains coexist in the crystal structure, the whole crystal of compound 20 is racemic and does not exhibit chirality. Neighboring helical chains polycatenated to each other and formed a 2D layer, then the adjacent 2D layers give rise to a 3D supramolecular structure by π-π interactions between the L2 ligands. Compound 21 contain meso-helical chains with a long pitch of 41.108(4) A. The acid ligands join neighboring Zn atoms to form a 1D zigzag chain. The final 3D framework of 21 is obtained by the interconnection with both meso-helical chains and zigzag chains. The simplified structure of 21 is a{42.6.83} net topology. The structure of compound 22 is a 2D framework, in which L3 ligands adopt both cis and trans configurations. From a topological perspective,22 represents{414.6} topology.