Flexible Dicarboxylate Research Articles

Structural Diversity in Six Mixed Ligand Zn(II) Metal–Organic Frameworks Constructed by Rigid and Flexible Dicarboxylates and Different N,N′ Donor Ligands

Three different N,N′-donor ligands with Zn(NO3)2·6H2O and two different dicarboxylates, flexible succinate (suc) and rigid fumarate (fum) afforded six different metal–organic frameworks (MOFs). Among the N,N′-donor ligands, one bent 1,4-bis(3-pyridyl)-2,3-diaza-1,3-butadiene (3-bpdb) gives two isostructural two-dimensional MOFs, {[Zn(3-bpdb)(suc)]·(H2O)2}n (1) and {[Zn(3-bpdb)(fum)(H2O)2]}n (2). The use of a straight N,N′-donor ligand, i.e., 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene (4-bpdb), results in two three-dimensional (3D) MOFs, {[Zn4(4-bpdb)2(suc)3(OH)2]·5(H2O)}n (3) and {[Zn(4-bpdb)(fum)]·(H2O)2}n (4). Here, 3 is a pillared layer structure, whereas 4 has a 5-fold interpenetrated dimondoid network. For both the bent and straight N,N′-donor ligands an imine alike motif is embedded in the structure. When this motif is replaced by a C–C double bond by using the ligand 1,2-bis(4-pyridyl)ethylene (bpee), it produces two MOFs, {[Zn(bpee)(suc)]2·(H2O)3}n (5) and {[Zn2(bpee)2(fum)2]·(H2O)}n (6), having a...

Urea-based flexible dicarboxylate linkers for three-dimensional metal-organic frameworks

The metal-organic frameworks (MOFs) 3D-[Mn2(L1)2(DMF)]·2DMF (1), 3D-[Cd2(L2)2(DMF)3] (3), [Zn2(L2)2(DMF)3] (4) and 3D-[Mn2(L2)2(DMF)3] (5) are the first examples of three-dimensional metal-organic networks constructed from a single ditopic dicarboxylate linker (i.e., without bridging co-ligands) with an urea group in the linker axis (L12− = 4,4′-(carbonylbis(azanediyl))dibenzoate; L22− = 4,4′-(carbonylbis(azanediyl))bis(3-methylbenzoate), DMF = dimethylformamide). From Cd2+and L12− a 1D coordination polymer 1D-[Cd(L1)(DMF)3] (2) is formed. The urea group is engaged in hydrogen bonding with the C(4)[R12(6)] motif to an oxygen atom of a DMF solvent (in 1) or a metal-coordinated carboxylate group (in 3–5). Network 1 has infinite channels with parallelepiped cross sections and 30% solvent-filled volume. The 3 D frameworks 3–5 are of diamond (6,6), dia topology with a single framework having large voids with 17.6 Å and 19.7 Å nodal separation. Thus, four symmetry-related nets interpenetrate, organized via H-bonds in the C(4)[R12(6)] motif, still leaving about 50% solvent-filled void volume in the fourfold interpenetrated structure.

Synthesis and structures of a series of d10 coordination compounds based on flexible bis(imidazole) ligand and dicarboxylates

ABSTRACTA series of new coordination compounds based on 1,6-bis(2-methyl-imidazole-yl)-hexane (bimh), namely [Zn(bimh)0.5(chda)]n (1), {[Cd(bimh)0.5(bda)]·H2O}n (2), [Cd(bimh)(oba)]n (3), [Zn(bimh)(oba)]n (4), [Cd(bimh)(ipa)]n (5), {[Zn(bimh)0.5(ipa)]·H2O}n (6), (bimh = 1,6-bis(2-methyl-imidazole-1-yl)hexane, H2chda = 1,4-cyclohexanedicarboxylic acid, H2bda = 2,2′-biphenyldicarboxylic acid, H2oba = 4,4′-oxybis(benzoic acid), and H2ipa = isophthalic acid) have been synthesized by solvothermal route and diffusion method and characterized by elemental analysis, IR spectroscopy, single-crystal X-ray diffraction technology. Compound 1 affords a two-dimensional (2D) wave-like framework with dinuclear paddle-wheel units, where the structures are further assembled via aromatic π–π stacking to generate a 3D network. Compound 2 exhibits a 1D ladder chain, which is further linked by hydrogen bonds to form a 2D architecture. Compounds 3 and 4 are isostructural, possessing a 2D layer network based on hydrogen bonds. Compound 5 displays a 2D wave-like layer structure. Compound 6 has a 1D line chain structure, which is packed into a 3D supermolecule network by two types of hydrogen bonds. Furthermore, the thermal stabilities and photoluminescent properties for compounds 1–6 were investigated.

Porosity and dye adsorption enhancement by ultrasonic synthesized Cd(II) based metal-organic framework

A Cd(II) based metal-organic framework, TMU-7, was synthesized by incorporation of V-shaped flexible dicarboxylate ligand and the N-donor pillar ligand using sonochemical method while morphology and size of particles were investigated and characterized by scanning electron microscopy and X-ray powder diffraction. Moreover, N2 adsorption was applied to examine the effect of synthesis method on porosity. Also TMU-7 was evaluated for its Congo red adsorption.

Syntheses, crystal structures and properties of two coordination polymers derived from flexible dicarboxylate and N-donor ligands

Two coordination polymers, namely [Zn3(PBDC)3(4,4′-bipy)]n (1) and [Co(PBDC)(4,4′-bipy)0.5]n (2) have been prepared via hydrothermal reactions of metal(II) nitrates with 1,4-bis(4-phenoxy)benzenedicarboxylic acid (H2PBDC) and 4,4′-bipyridine. Both complexes were characterized by elemental analyses, FT-IR, thermogravimetric analysis (TGA), powder X-ray diffraction and single-crystal X-ray diffraction. Structure analyses reveal that complex 1 possesses a (3,4,6)-connected 3D topology with point symbol of {4·92}2{42·68·8·92·102}{95·10}, while complex 2 has a 3D 4-fold interpenetrating framework with point symbol of {412·63}. In addition, the luminescent property of complex 1 and magnetic property of complex 2 were also studied.

A series of 1-D, 2-D and 3-D coordination polymers self-assembled from a flexible dicarboxylate and mixed N-donor ligands: syntheses, structural diversity, and luminescent properties

We have synthesized a series of metal–organic coordination frameworks under solvothermal conditions, formulated as [Cu(L)(phen)](1), [Co2(L)2(bib)]·CH3OH(2), [Co(L)(btmb)0.5](3), [Zn(L)(bib)]·2H2O(4), [Cu(L)(bib)]·DMF(5), and [Mn4(L)4(bimb)(CH3OH)](6) based on a flexible multicarboxylic bridging ligand 4,4′-methylenebis(oxy)-dibenzoic acid (H2L) and flexible N-donor ligands 1,4-bis (1H-imidazol-1-yl)-butane (bib), 1,4-bis(1H-1,2,4-triazol- 1-ylmethyl)benzene (btmb), and 1,4-bis(1H-imidazol-1-ylmethyl)benzene (bimb). The structures of the frameworks have been determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectra, and thermogravimetric analyses. The crystal structure determinations reveal that 1 has a 1-D Z-shape chain. Compounds 2 and 3 are 2-D twofold parallel interpenetrating 4-connected net with the Schläfli symbol {44·62}. Compound 4 is a 2-D threefold parallel interpenetrating 4-connected nets with the Schläfli symbol {44·62}. Compound 5 is 3-D 4-connected net with the Schläfli symbol {65·8}. Compound 6 is characterized by a three-dimensional framework with one-dimensional homogeneous Mn-carboxylate chain. We found that flexible carboxylate ligands have different coordination modes under different synthetic conditions. The flexible skeleton of ligands and the coordination angle between the ligand and the metal ion is described. The luminescence and thermogravimetric properties of these compounds have been investigated.

Lanthanide Metal-Organic Frameworks with Six-Coordinated Ln(III) Ions and Free Functional Organic Sites for Adsorptions and Extensive Catalytic Activities

Three chelating-amino-functionalized lanthanide metal-organic frameworks, Y-DDQ, Dy-DDQ and Eu-DDQ, were synthesized with a flexible dicarboxylate ligand based on quinoxaline (H2DDQ = N, N′-dibenzoic acid-2,3-diaminoquinoxaline). The three-dimensional framework is constructed by the H2DDQ linkers connecting the zigzag ladders, showing a net of sra topology. In the structures, one kind of Ln(III) ions metal centers are six-coordinated and thus can potentially behave as open metal sites (OMSs), while the free chelating amino groups can act as free functional organic sites (FOSs). The N2 and Ar adsorption behaviors indicate that these Ln-DDQ exhibits stable microporous frameworks with high surface area after remove of the solvents. Owing to presence of OMSs and FOSs, these MOFs show good ability of CO2, dyes captures and Lewis acid catalyst for cyanosilylation reaction. In view of the existing FOSs in the framework, Pd NPs were immobilized onto the MOFs through graft interactions between free chelating amino groups and metal ions precursor using postsynthetic modification. The well dispersed Pd@Ln-DDQs exhibit efficient and recyclable catalytic reduction of 4-nitrophenol to 4-aminophenol, and they can also act as an excellent catalyst for Suzuki-Miyaura cross-coupling reactions with the exposed Pd NPs.

Diverse topologies of three cobalt(II) coordination polymers constructed from flexible bis(benzimidazole) and dicarboxylate ligands

Three cobalt(II) coordination polymers {[Co(L1)(nda)(H2O)2]·2H2O} n (1), [Co(L2)(tbi)(H2O)] n (2) and [Co(L2)(bpdc)(H2O)] n (3) (L1 = 1,3-bis(5,6-dimethylbenzimidazol-1-yl)-2-propanol, L2 = 1,3-bis(benzimidazol-1-yl)-2-propanol, H2nda = 2,6-naphthalenedicarboxylic acid, H2tbi = 5-tert-butyl isophthalic acid and H2bpdc = 4,4′-biphenyldicarboxylic acid) were synthesized and characterized by physicochemical and spectroscopic methods. Complex 1 exhibits a 1D loop-like structure, which is further extended into a 3D 3,3,4T31 network through two O–H···O hydrogen bonding interactions. Complex 2 displays a 1D ladder-like chain, arranged into a 2D supramolecular network with 3,3,4L34 topology via classical O–H···O hydrogen bonding interactions, whereas complex 3 features a 2D 3,4L13 layer structure and further assembles into a 3D framework with a twofold interpenetrating sqc65 topology through O–H···O hydrogen bonding interactions. The fluorescence and catalytic properties of these complexes for the degradation of Congo red in a Fenton-like process have been investigated.

In situ hydrothermal syntheses, structures and photoluminescent properties of four novel metal-organic frameworks constructed by lanthanide (Ln=Ce(III), Pr(III), Eu(III)) and Cu(I) metals with flexible dicarboxylate acids and piperazine-based ligands

Four novel metal-organic frameworks,[Cu2Cl2(pyrz)]n (1) and (H2pip)n[Ln2(pydc)4(H2O)2]n (Ln=Ce (2), Pr (3) and Eu (4), H2pzdc=2,3-pyrazinedicarboxylic acid, pyrz=pyrazine, H2pydc=2,6-pyridinedicarboxylic acid, H2pip=piperazine) have been synthesized under hydrothermal conditions and characterized by the elemental analysis, ICP, Far IR (FIR), FT-IR spectra, TGA, single crystal X-ray diffraction analysis and powder X-ray diffraction (PXRD). Compound 1 is two-dimensional containing Cl-Cu-Cl sites, while the lanthanide complexes contain one-dimensional infinite Ln–O-Ln chains. All the complexes show high thermal stability. The complexes 1–3 exhibit luminescence emission bands at 584, 598 and 614nm at room temperature when excited at 300nm. Complex 4 exhibits bright red solid-state phosphorescence upon exposure to UV radiation at room temperature.

Bidimensional cadmium metal-organic frameworks based on 1,3-bis(4-pyridyl)propane displaying long lifetime photoluminescence emission

Bidimensional novel cadmium metal-organic frameworks (MOFs) based on the 1,3-bis(4-pyridyl)propane linker and flexible dicarboxylate ligands derived from glutarate (2-methylglutarate, 2-dimethylglutarate and 3-methylglutarate) have been synthesized by conventional routes. These MOFs show fascinating structural features and they display long lifetime photoluminescence emission in the solid state, at room temperature.

Syntheses, Structures and Photoluminescence of Three Cd(II) Coordination Polymers Based on Flexible Bis(Benzimidazole) and Dicarboxylate Ligands

Three new Cd(II) coordination polymers constructed from two structurally related ligands, 1,1′-(1,3-propane)bis-(2-methylbenzimidazole) (pbmb) and 1,1′-(1,4-butanediyl)bis(2-methyl-benzimidazole) (bbmi), have been hydrothermally synthesized: [Cd(pbmb)(hmph)] n (1), [Cd(pbmb)(chdc)] n (2) and [Cd(bbmi)0.5(chdc)] n (3), where H2hmph = homophthalic acid and H2chdc = 1,4-cyclohexanedicarboxylic acid. These complexes were structurally characterized by elemental analysis, IR, and single crystal X-ray diffraction analyses. Complex 1 possesses a two-dimensional 63 honeycombed network structure, which are further extended into a 3D supermolecule framework through weak C–H···O hydrogen bonding interactions. 2 displays an infinite 1D loop-like chain structure, which is further assembled into a 2D supramolecular layer via C–H···O hydrogen bonding interactions. In complex 3, CdII ions are connected by chdc2− anions to form a 1D chain containing binuclear clusters, which is further connected by the bbmi exhibiting a 2D (3,4)-connected network with a point symbol of {42·63·8}{42·6}. The thermal and photoluminescence properties of the three complexes were investigated in detail. Three Cd(II) coordination polymers constructed by flexible bis-(2-methylbenzimidazole) and dicarboxylate anions co-ligands. These compounds display diverse architectures from 1D to 2D. The various structures indicate that flexible dicarboxylate anions have a remarkable effect on the final structures and topologies.

Influence of the steric effect of flexible isomeric phenylenediacetic acids on the resultant lead(II) coordination polymers

To study the steric effect of the flexible dicarboxylate ligands on the resultant formations of coordination polymers (CPs), four new PbII CPs [Pb(1,2-pda)(H2O)]n (1), [Pb(1,3-pda)]n·nH2O (2), [Pb2(1,4-pda)2(H2O)]n·2nH2O (3a and 3b) have been produced by the isomeric phenylenediacetic acids (H2pda). The X-ray crystallography study reveals that CP 1 is a two-dimensional (2D) 4-connected sql (44.62) network via the weak Pb···O interactions built on 1D chain-like structure. CP 2 crystallizes in orthorhombic system with chiral space group P212121, showing a 4-connected sra (42.63.8) framework where a left-handed helical motif is formed by PbII ions and trans-1,3-pda ligands. More interestingly, CPs 3a and 3b are two true 3D polymorphs and have the different morphology. Topologically, the framework of 3a exhibits a 4-connected lon 66 motif, while that of 3b is a (4,6)-connected fsh (43.63)2(46.66.83) net. It is found that the three isomeric pda anions display the various coordination fashions in four CPs. The different structural arrangements show that the steric effect of the isomeric H2pda tectons has a positive role in directing the final products of PbII CPs. Also, the fluorescent properties of the CPs were studied in the solid state at room temperature.

Three N-H functionalized metal-organic frameworks with selective CO2 uptake, dye capture, and catalysis.

Three N-H functionalized metal-organic frameworks, Pb-DDQ, Zn-DDQ, and Cu-DDQ, were synthesized with a new flexible dicarboxylate ligand based on quinoxaline (H2DDQ = N,N'-dibenzoic acid-2,3-diaminoquinoxaline). CO2 adsorptions indicate that Zn-DDQ and Cu-DDQ have greatly enhanced the CO2 uptake due to the opposite N-H groups on pyrazine. With very small adsorption of N2, Cu-DDQ shows high selectivity for CO2 and N2. The three MOFs also have large adsorptions of some selected dyes, while Zn-DDQ and Cu-DDQ with large but different shapes of pores are demonstrated to be promising materials for fast separation of MB/other and CV/other mixtures, respectively. The cyanosilylation of aldehydes and ketones with high yields in a short reaction time for Cu-DDQ indicates that Cu-DDQ has a higher Lewis acidity than the other two MOFs.

Experimental, characteristic evidence and surface photovoltage properties of a series of Cu/Mn complexes with bipyrazolyl-pyridine and different spanning dicarboxylate

By introduction of different spanning flexible dicarboxylate as auxiliary ligands, novel complexes with N-heterocyclic ligand, [Cu(H2L)(ox)]·2H2O (1), [Cu2(HL)2(Hglu)]·2CH3OH·H2O (2), and [Mn(H2L)(ad)]·H2ad (3) (H2L=2,6-di-(5-methyl-1H-pyrazol-3-yl)pyridine, ox=oxalic acid, glu=glutaric acid, ad=adipic acid) are synthesized with hydrothermal method. Structural analysis reveals that the coordination modes of metal center in these complexes are various, in complexes 1 and 2, Cu(II) atom is five-coordinated to form a distorted square pyramid geometry. While in complex 3, Mn(II) atom is six-coordination mode, forming a distorted octahedron. In complexes 1–3, the N-heterocyclic ligand is coordinated with one or two metal centers. While in complexes 2 and 3, two metal centers are connected by bridging coordination fashions of flexible dicarboxylate and N-heterocyclic ligands, which are different from those in complex 1. In addition, the surface electron behaviors of complexes 1 and 3 have also been studied. The results show that the surface photovoltage (SPV) response signals increase when the positive electric field enhances in the range of 300–800nm. This result reveals that these complexes have the potential characterization of being able to trap photogenerated electron or hole, enhancing the separation extent and restrain the recombination of the photogenerated electron and hole.

A series of 3D isomorphous lanthanide coordination polymers based on flexible dicarboxylate ligand: Synthesis, structure, characterization, and properties

Seven lanthanide coordination polymers, namely, {[Ln(BDOA)1.5(H2O)]·H2O}n (Ln = Ce(I), Pr(II), Nd(III), Sm(IV), Eu(V), Gd(VI), and Tb(VII), H2BDOA = benzene-1,4-dioxydiacetic acid), have been synthesized through hydrothermal reactions of lanthanide nitrate with H2BDOA ligands and characterized by elemental analysis, infrared spectroscopy and single crystal X-ray diffraction. Findings indicate that I–VI are isomorphous and isostructural, containing the subunit of cavate 10-membered cages (Ln2O2(OCO)2), while VII possesses the subunit of cavate 14-membered cages (Tb2(OCO)4), based on which to assemble into three-dimensional porous architectures via BDOA2− ligands, hydrogen bonds and C–H⋯π interactions. I and III present antiferromagnetic behaviors and lanthanide contraction effect exists in I–VI. Luminescent studies suggest the typical intense emissions of Ln(III) ions occur in the visible region and therefore the coordination polymers display good selectivity towards some certain metal ions such as Ca2+ and Cd2+, showing promising potential as selective luminescent probes of these metal ions.

Cobalt(II) Coordination Polymers with Three-Dimensional Supramolecular Structure Based on Flexible Dicarboxylate and Imidazole-Containing Ligands

Cobalt(II) Coordination Polymers with Three-Dimensional Supramolecular Structure Based on Flexible Dicarboxylate and Imidazole-Containing Ligands

Different interpenetrated coordination polymers based on flexible dicarboxylate ligands: topological diversity and magnetism

This work evidently indicates that the effect of the secondary ligands, molar ratios and geometric preferences of the metal centers are critical on the resulting entangled motifs.

Flexible dicarboxylate based pillar-layer metal organic frameworks: differences in structure and porosity by tuning the pyridyl based N,N′ linkers

Dicarboxylate supported metal organic hybrids of Co(II), Zn(II) and Cd(II) have been synthesized using two different pyridyl based N,N′ linkers having Schiff base functionalized site. The use of flexible dicarboxylate glutarate in designing such frameworks has created a marked diversity in topology. The different N,N′ donor linkers also played an active part in the channel modification in the synthesized MOFs. The structural and topological diversity has been analyzed from the single crystal X-ray structure. Five compounds, {[Co(azpy)(glut)]·(CH3OH)}n (1), {[Co(meazpy)(glut)(H2O)2]·(H2O)3}n (2), {[Zn(azpy)0.5(glut)(H2O)]·(azpy)0.5}n (3), {[Zn(meazpy)0.5(glut)(H2O)]·(H2O)2}n (4) and {[Cd(azpy)(glut)]·(CH3OH)}n (5), show porous structures with solvent accessible voids. The nature of the pores as well as the existence of lattice solvent molecules in 1 and 2 are different due to the use of a different pillar ligand in their fabrication. In case of 3 and 4 there are some nice effects of non-covalent interaction in the construction of their solid state structure, which has also originated by the change of pillar N,N′ donor linkers. Complex 5 is topologically as well as structurally similar to 1 forming a 2D-grid like structure. In {[Cd2(meazpy)2(glut)(NO3)]2}n (6) there is a formation of 2D sheets with the coordinated counter anion. Interestingly, here the sheets are disposed in a perpendicular fashion to each other and do not contain any solvent accessible void. Upon removal of the solvent molecules, the frameworks 1–5 show moderate CO2 and H2 uptake at 273 K and 77 K, respectively. The desolvated frameworks show different quantities of CO2 and H2 uptake which has been corroborated to their structures.

Bis-thiourea macrocycles incorporating fused [n]polynorbornanes: binding of flexible versus rigid dicarboxylates

Two macrocyclic bis-thiourea hosts 5 and 6 were constructed and their interactions with two dicarboxylates of similar size (pimelate = flexible and terephthalate = rigid) were evaluated using 1H NMR titration techniques. In contrast to previous work with thiourea functionalised [n]polynorbornanes (where a notable increase in H:G affinity was noted for the rigid guest), the new macrocyclic hosts, in particular host 6, bind pimelate more strongly than terephthalate (for 6 binding pimelate log Ka = 4.7, terephthalate log Ka = 3.7). A binding arrangement in which the flexible dicarboxylate is ‘perched’ above the macrocycle is proposed to justify these results.

Syntheses, crystal structures, and magnetic properties of four one-dimensional metal–nitroxide coordination polymers linked by flexible dicarboxylate anions

Four new one-dimensional coordination polymers [Co(IM4Py)2(adi)(H2O)2] n , [Zn(IM4Py)2(adi)(H2O)2] n , [Cd(IM4Py)2(adi)(H2O)2] n , and [Ni(IM4Py)2(glu)(H2O)2] n (IM4Py = 2-(4′-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl, adi = adipate anion and glu = glutarate anion) were synthesized and structurally characterized. The single-crystal X-ray analyses indicate that all four complexes crystallize in neutral one-dimensional chains in which the nitroxide–metal–nitroxide units are bridged by the flexible dicarboxylate anions. The adipate anions adopt the anti/gauche/anti and anti/anti/anti conformations in the Co(II), Zn(II), and Cd(II) complexes, while the glutarate anions only possess the anti/anti conformation in the Ni(II) complex. The magnetic properties of the Co(II) and Ni(II) complexes show the occurrence of weak antiferromagnetic interactions between the metal atoms and the nitroxide radicals.