Different two-dimensional metal-organic frameworks through ligand modification

Through ligand modification, we have replaced the central benzene ring of H₂TDBA ([1,1′:3′,1″-terphenyl]-4,4″-dicarboxylic acid) with the pyridine structurally related ligand H₂PDDA (4,4′-(pyridine-2,6-diyl)dibenzoic acid), which makes the central pyridine ring of H₂PDDA more coplanar with two benzene rings on both sides of the ligand. The modification results in a dramatically different linkage configuration, thereby allowing structural changes to the metal-organic frameworks (MOFs). Two 2-D MOFs, [Cu(TDBA)(DMA)₂]·H₂O (BUT-221, DMA = N,N-dimethylacetamide), and [Cu₃(PDDA)₃(DMA)₂(H₂O)]·5H₂O (BUT-223) have been synthesized through reactions of two ditopic carboxylate ligands with Cu(NO₃)₂·3H₂O under solvothermal conditions, and characterized by single-crystal X-ray diffraction, powder X-ray diffraction, thermogravimetric analysis and infrared spectroscopy. Topological analysis shows that BUT-221 is a twofold parallel interpenetrating 4⁴ 2-D network with a skl topology, while BUT-223 is a 2-D network with a kgm topology.     

Nanocage containing metal-organic framework constructed from a newly designed low symmetry tetra-pyrazole ligand

1368-Tetra(1H-pyrazol-4-yl)-9H-carbazole (H₄CTP), a tetra-pyrazole ligand with C_s symmetry, has been synthesized based on a carbazole core. A solvothermal reaction of this ligand with NiCl₂·6H₂O gave a three-dimensional (3-D) metal-organic framework (MOF), [Ni(H₄CTP)Cl₂]·nS (BUT-41), which crystallized in the cubic space group Pm-3 in spite of H₄CPT with a central carbazole core and four peripheral pyrazole rings has low symmetry. The framework of BUT-41 can be regarded as a four-connected 3-D net with the rhr topology when both the organic ligand and the metal center are considered as four-connected nodes. Nanocages with internal diameter of 2 nm are present in the framework of BUT-41, which are formed by interconnecting 12 H₄CTP ligands and 20 Ni(II) ions. Each nanocage connects with six adjacent cages through sharing hexagonal windows with diameter over 7 Å, resulting in 3-D intersecting channels of the MOF. Although the tetra-pyrazole ligand is not deprotonated after coordination with the metal ions, powder X-ray diffraction and N₂ adsorption experiments reveal that the framework of BUT-41 is rigid and permanently porous with the Brunauer-Emmett-Teller surface area up to 1551 m² g^?1. Furthermore, gas adsorption experiments show that this MOF selectively adsorbs CO₂ over N₂ and CH₄.     

New copper(II) complexes including pyridine-2,5-dicarboxylic acid: synthesis,spectroscopic, thermal properties,crystal structure and how these complexes interact with purified PON 1 enzyme

We report the synthesis of two square-pyramidal copper(II) complexes, [Cu(2,5-pydc)(2-aepy)(H₂O)]·H₂O, 1, and [Cu(2,5-pydc)(2-ampy)(H₂O)]·H₂O, 2 (2-aepy = 2-(aminoethyl)pyridine, 2-ampy = 2-(aminomethyl)pyridine, 2,5-pydc = pyridine-2,5-dicarboxylic acid or isocinchomeronic acid). The synthesized complexes have been characterized by X-ray diffraction, FT-IR, elemental, and thermal analysis techniques. The crystal structure of 1 was established by X-ray analysis. Powder X-ray diffraction analysis showed that the complexes are pure. The inhibition of human serum paraoxonase 1 (PON 1, EC 3.1.8.1) enzyme with these complexes were investigated. We used diethyl 4-nitrophenyl phosphate as a substrate to measure the paraoxonase activity of PON 1 enzyme spectrophotometrically. Complexes 1 and 2 decreased the in vitro PON 1 activity with different inhibition mechanisms. Complexes 1 and 2 inhibited paraoxonase activity of this enzyme as competitively and noncompetitively, respectively.     

Synthesis,crystal structures and photoluminescent properties of two Cd(II)/Zn(II) coordination polymers with rarely 8-/2-fold interpenetrated based on 4,4′-stilbenedicarboxylic acid and imidazole ligands

Two coordination polymers, [Cd(sbdc)(bmib)]_n (1) and {[Zn(sbdc)(tib)]·0.5H₂O}_n (2) (H₂sbdc = 4,4′-stilbenedicarboxylic, bmib = 1,4-bis(2-methylimidazol-1-yl)butane, tib = 1,3,5-tris(1-imidazolyl)benzene), have been synthesized under solvothermal conditions, characterized by elemental analysis, infrared spectra, thermogravimetric analysis, and single-crystal X-ray diffraction. Single-crystal X-ray diffraction analysis reveals that 1 and 2 show 8-fold and 2-fold interpenetrating 3-D frameworks, respectively. Complexes 1 and 2 display a 4-connected (6⁶) sqc6 and a 4-connected (4⁴·6²) sql topology, respectively. Photoluminescent and thermal properties of 1 and 2 have also been investigated.     

Synthesis,crystal structure,and third-order non-linear optical properties of a new Cd(II) polymer constructed from pyrazine-2-carboxylic acid

A new cadmium(II) pyrazine-2-carboxylate coordination polymer, {[Cd(L)(H₂O)₂(SO₄)_0.5]₂·H₂O}_n (1) (HL = pyrazine-2-carboxylic acid), has been synthesized by low-temperature solid-state reaction. Single-crystal X-ray analyses reveal that 1 possesses a 3-D framework structure. The polymer 1 was characterized by elemental analyses, thermogravimetric analyses, X-ray powder diffraction analyses, IR spectra, and UV–visible spectra. The third-order non-linear optical properties were also investigated and they exhibit nice non-linear absorption and self-defocusing performance with modulus of the hyperpolarizability (γ) 1.30 × 10^?30 esu for 1 in a 2.01 × 10^?4 M?dm^?3 DMF solution.     

The syntheses,crystal structure,thermal analysis,and anticancer activities of novel dipicolinate complexes

[Cu(pydc)(eim)₃]?H₂O (1), [Cu(pydc)(4hp)(H₂O)] (2), and [Ni(pydc)(3hp)(H₂O)₂][Cu(pydc)(3hp)(H₂O)₂]?3H₂O (3) (H₂pydc = 2,6-pyridinedicarboxylic acid or dipicolinic acid, eim = 2-ethylimidazole, 4hp = 4-hydroxypyridine, 3hp = 3-hydroxypyridine) were synthesized and characterized by elemental analysis, spectroscopic measurements (UV–vis and IR spectra), and single-crystal X-ray diffraction. Crystal analysis revealed that the complexes extended to 3-D supramolecular networks through intermolecular H-bonding and molecular interactions between the ligand moieties and water molecules. The thermal stabilities of complexes are investigated by thermogravimetry, differential thermogravimetry, and differential thermal analysis techniques. The effects of complexes on the proliferation of HT-1080 fibrosarcoma cells were investigated using the quick cell proliferation assay. The cell viability changes were found to depend on the concentrations and type of complex.     

Coordination polymers constructed from an asymmetric dicarboxylate and N-donors: preparation,characterization, and properties

Two new coordination polymers with an asymmetric dicarboxylate and 4,4′-bipyridine ligand, {[Co(bpy)(H₂O)₄]·(cpa)·0.5H₂O}_n (1) and {[Ag(cpa)(bpy)][Ag(bpy)]·4H₂O}_n (2) (H₂cpa = 4-(2-carboxyethyl)benzoic acid, bpy = 4,4′-bipyridine), have been hydrothermally synthesized and characterized by elemental analysis, FT-IR spectroscopy, and single-crystal X-ray diffraction. Compound 1 displays a linear chain with guest molecule (cpa)^2? ions existing in the structure. Compound 2 contains two independent units, [Ag(cpa)(bpy)]^– (A) and [Ag(bpy)]⁺ (B), which form a 1-D + 1-D structure. A shows a 1-D chain structure bearing hooks formed by the carboxylates and organized into a tubular structure by hydrogen-bonding interactions. B has linear chains formed from Ag⁺ and bpy. The A and B chains co-crystallize with waters of crystallization to provide two linear [Ag(bpy)]⁺ chains embedded in the tubular structure formed by A via π…π stacking contacts. In 1 and 2, hydrogen-bonding and π…π stacking interactions connect the discrete 1-D chains into 3-D supramolecular structures. The fluorescent properties, TG analysis, and X-ray powder diffraction patterns for 1 and 2 were also measured.     

The synthesis,characterization, and theoretical hydrogen gas adsorption properties of copper(II)-3,3′-thiodipropionate complexes with imidazole derivatives

Three new coordination polymers, [Cu(μ₃-tdp)(im)₂]_n (1), {[Cu(μ₃-tdp)(1-mim)₂]·0.5H₂O}_n (2) and {[Cu₂(μ₃-tdp)₂(4-mim)₄]·H₂O}_n (3) [tdpH₂ = 3,3′-thiodipropionic acid, im = imidazole, 1-mim = 1-methylimidazole and 4-mim = 4-methylimidazole], have been prepared and characterized by spectroscopic techniques (IR and UV–Vis), elemental analyzes, magnetic measurements, thermal analyzes, and single-crystal X-ray diffraction. Complexes 1–3 crystallize in the monoclinic system with space groups of C2/c and P2₁/c, respectively. In 1–3, tdp is a bridging ligand to form 1-D chains, which are extended into a 2-D layer by hydrogen bonding and π···π interactions. The 3,3′-thiodipropionate exhibits an unexpected coordination mode in 1–3. Simulations were used to assess the potential of the complexes in H₂ storage applications.     

A two-fold interpenetrating porous metal–organic framework with a large solvent-accessible volume and selective sensing of nitroaromatic explosives

A cadmium(II) 3-D porous metal–organic framework, (Me₂NH₂)₄[Cd₂(TTCA)₂Cl₂]·7DMF·2Diox·6H₂O (1) (TTCA = triphenylene-2,6,10-tricarboxylate, DMF = N,N-dimethylformamide, diox = 1,4-dioxane), has been synthesized through solvothermal conditions. Single-crystal X-ray analysis reveals that the structure of 1 has a two-fold interpenetrating framework with a large solvent-accessible volume of 52% per unit cell. The result of topological analysis shows that 1 is a (3,3)-connected 3-D network with {10³} topology. Luminescence tests illustrate that 1 can selectively sense nitroaromatic explosives via a luminescence quenching mechanism.     

2-D coordination polymers of copper and cobalt with 3,4-pyridinedicarboxylic acid: synthesis,characterization, and crystal structures

Two new complexes involving 3,4-pyridinedicarboxylic acid (3,4-H₂pdc), copper(II) and cobalt(II) complexes, {[Cu(3,4-Hpdc)₂(H₂O)₂]·2dmso}_n (1) and {[Co(3,4-Hpdc)₂(H₂O)₂]·2H₂O·2dmso}_n (2) (dmso = dimethylsulfoxide), have been synthesized by the diffusion method and characterized by elemental analysis, IR spectroscopy, thermal analysis, powder and single-crystal X-ray diffraction analysis, and electron paramagnetic resonance (EPR). In both compounds, the metal coordination sphere is composed of a trans-MO₄N₂ core and adopts a distorted octahedral geometry in accordance with X-ray diffraction and EPR results. 3,4-Hpdc^? ligands bridge the metal centers giving two-dimensional (2-D) coordination polymers with four-connected uninodal nets of (4,4) topology.     

Syntheses,crystal structures,and luminescent properties of three metal coordination polymers based on adipic acid and 2-(pyridine-3-yl)-(1H)-benzimidazole

Three new metal coordination polymers constructed from adipic acid and 2-(pyridin-3-yl)-(1H)-benzimidazole ligands, [M(ADP)(3PBI)₂(H₂O)₂]·2H₂O (M = Ni and Co for 1 and 2, respectively) and [Cd(ADP)(3PBI)(H₂O)] (3) [ADP = adipic acid dianion; 3PBI = 2-(pyridin-3-yl)-(1H)-benzimidazole], have been synthesized by hydrothermal reactions and were characterized by X-ray single-crystal diffraction, elemental analyses, IR, powder X-ray diffraction, and thermogravimetry. Complexes 1 and 2 are isostructural. Both form a 1-D linear chain structure, which is further assembled into a 3-D supramolecular framework by π?π stacking and hydrogen bonding interactions. Complex 3 possesses a binuclear unit and displays a 2-D layer which is further extended to a 3-D supramolecular architecture via hydrogen bonding and other weak packing interactions. The luminescent properties of 3 were investigated in the solid state at room temperature.     

A blue luminescent binuclear cadmium-orotate coordination polymer: synthesis,crystal structure,and thermogravimetric analysis

Assembly of orotic acid (H₃Or, 1,2,3,6-tetrahydro-2,6-dioxo-4-pyrimidinecarboxylic) and Cd(NO₃)·6H₂O yielded a coordination polymer, [(Cd(Hor)·2.5H₂O)₂]_n (1), which has been characterized by X-ray single-crystal diffraction, TGA, and ?uorescence spectra. Single-crystal X-ray structural analyses reveal that 1 is a hydrogen-bonded binuclear Cd-orotate coordination polymer in which both Cd²⁺ ions have different coordination environments with identical distorted octahedral geometry. Crystal data for 1: monoclinic, space group P2₁/n, a = 7.0209(10) Å, b = 13.974(2) Å, c = 17.541(3) Å, β = 98.842(2)°, V = 1700.5(4) Å, Z = 4, R1 = 0.0269, wR2 = 0.0612, θ_max = 25.960. The emission spectrum of the Cd-complex recorded with 265 nm excitation wavelength reveals the complex has strong blue luminescence with the peak maximum 420 nm (2.95 eV) as a result of the n–π* and π–π* transitions on the H₃Or ligand.     

Syntheses,structural determination,and binding studies of nine-coordinate multinuclear (mnH)2[EuIII(egta)]2·6H2O and binuclear (mnH)4[EuIII2(dtpa)2]·6H2O

Two lanthanide complexes, (mnH)₂[Eu^III(egta)]₂·6H₂O (1) (H₄egta = ethyleneglycol-bis-(2aminoethylether)-N,N,N′,N′-tetraacetic acid) and (mnH)₄[Eu^III₂(dtpa)₂]·6H₂O (2) (H₅dtpa = diethylenetriamine-N,N,N′,N″,N″-pentaacetic acid), have been synthesized and characterized by FT-IR spectroscopy, thermal analysis, and single-crystal X-ray diffraction. X-ray diffraction reveals that 1 is multinuclear nine-coordinate and crystallizes in the monoclinic crystal system with space group C2/c. The obtained cell dimensions are a = 38.513(3)?Å, b = 13.5877(8)?Å, c = 8.7051(5)?Å, β = 99.6780(10)°, and 4490.6(5)?ų. Each methylamine (mnH⁺) cation in 1, through hydrogen bonds, connects three adjacent [Eu^III(egta)]^? anions. The [Eu^III(egta)]^? anions connect one another forming a 1-D multinuclear zigzag chain structure along the c-axis. Complex 2 is nine-coordinate binuclear structure with tricapped trigonal prismatic conformation and crystallizing in the monoclinic crystal system, but with space group P2₁/n. The obtained cell dimensions are a = 9.9132(8)?Å, b = 24.1027(18)?Å, c = 10.7120(10)?Å, β = 109.1220(10)°, and 2418.2(3)?ų. For 2, there are two kinds of methylamine cations (mnH⁺) connecting [Eu^III₂(dtpa)₂]^4? complex anions and lattice waters through hydrogen bonds, leading to formation of a 2-D ladder-like layer structure.     

Preparation,structure and photocatalysis of metal-organic frameworks derived from aromatic carboxylate and imidazole-based ligands

Three 3-D metal-organic frameworks (MOFs), [Cd(NDC)(biim-4)]·0.5H₂O (1), [Cd₂(TDC)₂(biim-4)₂(H₂O)₂] (2) and [Zn₂(biim-4)₂(TDC)₂]·2.5H₂O (3) (biim-4 = 1,4-bis(1-imidazolyl) butyric alkyl; H₂NDC = 1,4-naphthalene dicarboxylic acid; H₂TDC = thiophene-2,5-dicarboxylic acid), have been synthesized under hydrothermal conditions and structurally characterized by single X-ray diffraction. The three MOFs have high photocatalytic degradation effects on methyl orange under UV irradiation. Through electronic structure analysis combined with time-dependent density functional theory calculations, catalytic performances of these materials are correlated with the molecular composition and the optoelectronic properties of the samples.     

A fluorescent 3-D metal-organic framework with unusual tetranuclear zinc secondary building units

A 3-D metal-organic framework (MOF) {Zn₄(μ₃-OH)₂(bdc)₃(pad)₂}·2H₂O (1, H₂bdc = 1,4-benzenedicarboxylic acid, pad = 1,10-phenanthroline-5,6-dione) with unusual Zn₄(μ₃-OH)₂(COO)₆(N₂)₂ secondary building units (SBUs) has been hydrothermally synthesized and characterized by single crystal X-ray diffraction, powder X-ray diffraction, thermogravimetric analysis, elemental analysis, and infrared spectroscopy. The tetranuclear Zn₄ SBU was formed through two dinuclear Zn₂ clusters by sharing two μ₃-OH bridges. Considering this Zn₄ SBU as a six-connected node, the overall framework of 1 has a pcu topology. This tetranuclear Zn₄ SBU can be used as a node in construction of MOFs.     

Synthesis,characterization, and structural determination of copper(II) complexes with alkyl derivatives of hydroxybenzophenones

Four mononuclear copper(II) complexes, [Cu(LFQM-115)₂] (1), [Cu(LFQM-116)₂] (2), [Cu(LFQM-117)₂] (3) and [Cu(octyloxy)₂] (4) [LFQM-115 = 2-hydroxy-4-O-methylbenzophenone (C₁₄H₁₁O₃), LFQM-116 = 2-hydroxy-4-O-butylbenzophenone (C₁₇H₁₈O₃), LFQM-117 = 2-hydroxy-4-O-(33-dimethylallyl)benzophenone (C₁₈H₁₈O₃) and octyloxy = 2-hydroxy-4-O-octylbenzophenone (C₂₁H₂₅O₃)], have been prepared and investigated by infrared spectroscopy, thermal analysis, and powder and single crystal X-ray diffraction. Even though the synthesis and infrared analysis of 1, 2, and 4 have been reported previously, their crystal structures were elucidated for the first time here. In addition, the crystal structures of LFQM-116 and LFQM-117 were also determined by single crystal X-ray diffraction. The pseudo-translational symmetry found in LFQM-116 and the isomorphism between LFQM-115 and LFQM-117 are discussed. The complexes were prepared from a reaction of copper(II) nitrate trihydrate and the respective ligand in a (1:2) molar ratio in methanol (for 1 and 2) or THF (for 3 and 4) with addition of NaOH. Furthermore, crystallographic studies show that each copper(II) exhibits a square planar geometry, coordinated by four oxygens of two ligands. The nature and crystal packing of the intermolecular interactions are discussed. Compounds 2 and 3 are isomorphic crystals and all structures have the same supramolecular synthon.     

Synthesis,characterization, and magnetochemical properties of two Mn4 clusters derived from 2-pyridinecarboxaldehyde Schiff base ligands

Two tetranuclear manganese complexes, [Mn₄(L¹)₆](ClO₄)₂?2.75H₂O (1) [HL¹ = 4-methyl-2-((pyridin-2-ylmethylene)amino)phenol] and [Mn₄(L²)₄(NO₃)₃(OH)]?pz?3H₂O (2) [HL² = (1H-pyrazol-1-yl)(pyridin-2-yl)methanol, pz = pyrazole], have been synthesized and characterized by IR spectroscopy, elemental analysis, single-crystal X-ray diffraction, and magnetic measurements. The structural analysis revealed that the central manganese ion is linked with three apical manganese ions through six phenoxo-bridges creating a Mn₄O₆ core for 1; 2 has a cubane-like topology with the Mn(II) ions and the deprotonated oxygens from L² alternatively occupying vertices. The magnetic studies indicated a weak ferromagnetic coupling interaction (J = 0.48 ± 0.087 cm^?1, g = 2.00, θ = ?0.78 K) for 1 and a weak antiferromagnetic spin-exchange interaction (J₁ = ?0.50 ± 0.075 cm^?1, J₂ = ?0.13 ± 0.082 cm^?1, g = 1.98) between Mn(II) ions for 2. The magnetostructural correlations of the two Mn₄ clusters have been discussed tentatively.     

Variation in crystalline architectures through supramolecular interactions in copper(II) complexes with tridentate N2O donor Schiff bases

Three copper(II) complexes, [Cu(L¹)(H₂O)(ClO₄)]·0.5H₂O (1), [Cu(L²)(H₂O)(ClO₄)]·0.5H₂O (2), and [Cu(L²)(NCNC(OCH₃)NH₂)]ClO₄ (3), where HL¹ = 4-bromo-2-(-(quinolin-8-ylimino)methyl)phenol and HL² = 1-(-(quinolin-8-ylimino)methyl)naphthalen-2-ol, have been prepared and characterized by elemental analysis, IR, UV–vis and fluorescence spectroscopy and single-crystal X-ray diffraction studies. The copper(II) centers assume five-coordinate square-pyramidal geometries in 1 and 2, whereas square planar copper(II) is present in 3. A methanol molecule has been inserted in the pendant end of the ligated dicyanamide in 3. Various supramolecular architectures are formed by hydrogen bonding, π?π, C–H?π, and lp?π interactions.     

Syntheses,structures and luminescent properties of a series of ladder-shaped [Ln2Sr3] heterometal-organic frameworks

A series of Ln^III–Sr^II heterometallic coordination polymers formulated as [Ln₂Sr₃(pda)₆(H₂O)₁₈]·nH₂O (Ln = Pr-1, n = 14; Nd-2, n = 12; Sm-3, n = 11; Eu-4, n = 11; Gd-5, n = 16; Tb-6, n = 13; Dy-7, n = 13) were synthesized via assembly of Ln(NO₃)₃·6H₂O, SrCl₂·6H₂O, pyridine-2,6-dicarboxylic acid (H₂pda) and imidazole (im) in H₂O/C₂H₅OH solution. Single crystal X-ray diffraction revealed that they are isostructural. All of these complexes possess ladder-shaped 1-D chain structures. The luminescent properties of Sm-3, Eu-4, Gd-5, Tb-6 and Dy-7 have been investigated. The solid-state quantum yields and the lifetimes of Eu-4 and Tb-6 are also studied.     

A supramolecular organic framework with ant topology featuring interdigitation and interpenetration

H₄BOPTC reacts with IMI to yield a supramolecular organic framework, formulated as [IMIH⁺]₂√[H₂BOPTC^2 ? ]√0.5H₂O (1) (IMI = imidazole, H₄BOPTC = benzophenone-3,3′,4,4′-tetracarboxylic acid). Single-crystal X-ray diffraction analysis reveals that 1 shows a novel architecture with two-level hierarchical entanglement. H₂BOPTC^2 ?  connects to IMIH⁺ through hydrogen bonds, providing 1D ribbon. The basic ribbons are entangled into a 3D net with ant topology. Then the ant nets further interpenetrate to give the final entangled framework. The thermal stability, optical band gap energy and photoluminescent property of 1 have also been investigated.