A water-stable metal-organic framework as a luminescent Fe~(3+) sensor under weak acidic and weak basic conditions

A three-dimensional(3 D) metal-organic framework(MOF) ZnL·0.5 H_2O·0.75 DMF(H_2L=9-(pyridin-4-yl)-9 H-carbazole-3,6-dicarboxylic acid, DMF=N,N-dimethylformamide) has been synthesized under solvothermal condition. Crystal structure analysis shows that, in ZnL, each dinuclear Zn_2(COO)_2 unit is doubly-bridged to the other two by the carbazole moieties to form the 1 D chains, which are further connected together by pyridine moieties to lead to the 3 D framework. ZnL exhibits both high structural stability and good luminescent stability in water with the pH range of 4–10. ZnL displays the luminescent quenching response for Fe~(3+) in water with good linear correlation between the quenching efficiency and the concentration with K_(sv) of 10800 M~(-1) in the low concentration range of 0–0.1 mM. Interestingly, it is observed that the sensing performance for Fe~(3+) is stable in the pH range of 4–9, enabling ZnL to detect Fe~(3+) ions in weak acidic and weak basic solutions.     

A novel pillared-layer-type porous coordination polymer featuring three-dimensional pore system and high methane storage capacity

Solvothermal reaction of Zn(NO_3)_2, 4-(1H-pyrazol-4-yl)pyridine(Hpypz) and 1,3,5-benzenetricarboxylic acid(H_3btc) in N,N-dimethylacetamide(DMA) produced a new porous coordination polymer [Zn_5(pypz)_4(btc)_2](1). Single-crystal X-ray diffraction study of 1 showed that deprotonated pypz~– ligands served as 1,2,4-triazolate-like ligands, linking Zn(II) ions to form porous two-dimensional(2-D) sql-a layers {Zn(pypz)}~+, which were further connected by eight-legged pillars {Zn_2(btc)_4(H_2O)_2}~(8–) based on the typical paddlewheel dinuclear Zn_2(RCOO)_4(H_2O)_2 cluster to form a novel type of non-interpenetrated pillared-layer framework with 3-D intersecting pore system and large pore volume. Gas sorption measurements revealed that 1 possesses large BET surface area of 2061 m~2 g~(–1) and very high methane total uptake of 245 cm~3(STP) cm~(–3) at 298 K and 65 bar.     

Layered and three-dimensional uranyl–organic assemblies with 4,4′-oxidiphthalic acid

Hydrothermal reactions of uranyl nitrate and 4,4'-oxidiphthalic acid(H_4L) resulted in the formation of three new uranyl-organic framework materials,namely(NH_4)_2[(UO_2)_3(L)_2]·5H_2O(1),(NEt_4)[(UO_2)_3(H_2O)(L)(HL)](2) and(UO_2)_7(H_2O)_2(phen)_4(L)_2(HL)_2(3)(NEt_4 = tetraethylammonium,phen = 1,10-phenanthroline).These three structures all comprise common uranyl pentagonal bipyramids.In 1,UO_7polyhedra are linked by hexadentate ligands to form a 3D framework with 1D channels,in which are located NH_4~+ ions and water molecules.While in 2,the organic ligands adopt pentadentate and hexadentate coordination modes,ligating UO_7 units to create a layered structure with channels filled by NEt_4~+ ions.For 3,uranyl square bipyramids are also accommodated together with pentagonal bipyramids,which are linked by tetradentate carboxylate ligands to produce the layered assembly.Phen molecules also coordinate to the uranyl centers to build up the structure.Luminescent studies indicate that 2 and 3 exhibit the characteristic uranyl emission.     

Steric Effect Modulating the Structures of Trinuclear Zinc Carboxylate Frameworks

By the reaction of different aromatic dicarboxylic acid with zinc nitrate, three metal-carboxylate frameworks, [Zn_3(BDC)_3(EtOH)_2](1), [Zn_3(BDC)_3(py)_2]·2DMF(2), and [Zn_3(NH_2-BDC)_3(H_2O)_2]·5DMF(3) which are constructed on the same linear trinuclear Zn_3(RCOO)_6 secondary building units, have been synthesized and characterized by X-ray diffraction analyses. Structural analyses showed that there are terephthalic acids as ligand linkers to form the hxl topological layer structures for 1 and 2. The introduction of the rigid aromatic ring pyridine in 2 as the terminal co-ligand of Zn3-SBU to instead of the flexible ethanol in 1, will form the layer-pillared supramolecular systems with 2-D crisscross channels, through its π-π stacking interactions. Owing to the steric hindrance of amino groups, 3 was assembled into a three-dimensional porous structure with pcu topology derived from the 2-amino-terephthalic acid as linkers to connect the Zn3-SBUs through a head-to-tail type.     

Construction of a New(4,8)-Connected Coordination Polymer Based on the Zinc Cluster: Structure,Topology, and Luminescence

The title complex, [Zn_3(L)_2(H_2 O)_2]_n(1, H_3 L = 5-((3-formylphenoxy)methyl)isophthalic acid), has been synthesized under hydrothermal conditions and structurally characterized by single-crystal X-ray diffraction, IR spectroscopy and thermogravimetric analysis. Compound 1 exhibits a 3D binodal(4,8)-connected net based on trinuclear [Zn_3(COO)4] clusters with the topology symbol of(4~(16)·6~(12))(4~4·6~2)_2. It crystallizes in monoclinic system, space group P2_1/c, with a = 13.548(3), b = 13.291(3), c = 8.2750(1) ?, β = 97.08(3)°, V = 1478.7(6) ?~3, Z = 2, M_r = 858.6 g/mol, D_c = 1.928 mg/m~3, μ = 2.49 mm-1, F(000) = 864, GOOF = 1.12, the final R = 0.0457 and wR = 0.1329 for 4334 observed reflections with I 2σ(I). Additionally, the photoluminescent behaviours of 1 and H3 L have also been investigated in the solid state at room temperature.     

Hydrothermal Synthesis,Crystal Structure and Luminescence Property of a 2D Manganese(Ⅱ) Coordination Polymer

Solvothermal reactions of MnCl_2·4H_2O with(pyridin-2-yl)methyl 4-(2-(4-((pyridin-2-yl)methoxy)phenyl)diazenyl)benzoate(L1) via an in situ ligand transformation reaction produced a new coordination polymer, {[Mn_(2.5)Cl_3L_2(H_2O)]·H_2O}_n(1, where HL = 4-(2-(4-((pyridin-2-yl)methoxy)phenyl)diazenyl)benzoic acid). The L1 ligand was decomposed in situ to L~- which was coordinated with Mn(Ⅱ) to form compound 1 in the solvothermal synthesis process. Complex 1 was characterized by IR spectroscopy, powder X-ray diffraction and single-crystal X-ray diffraction.Compound 1 possesses a 2D network. In addition, stability and photoluminescent property of 1 were also investigated.     

Lanthanide-organic frameworks based on terphenyl-tetracarboxylate ligands: syntheses,structures, optical properties and selective sensing of nitro explosives

Three isostructural three-dimensional(3D) lanthanide-based metal-organic frameworks [Ln_2L(H_2L)(NMP)_2].H_2O(Ln=Sm(1), Eu(2), Gd(3); H_4L=1,1′:4′,1″-terphenyl-2′,4,4″,5′-tetracarboxylic acid; NMP=N-methyl-2-pyrrolidone) have been synthesized and structurally characterized. In 1–3, two Ln3+ ions are doubly-bridged by two oxygen atoms of two carboxylate groups to form the dinuclear Ln_2(OCOO–)_2 unit. Each Ln_2(OCOO–)_2 unit links with four H_2L~(2-) ligands and four L4. ligands to lead to the 3D framework,which can be rationalized as a new trinodal 4,4,8-connected(44.62)(45.6)(412.616) topological network by considering the dinuclear Ln_2(OCOO–)_2 units as 8-connected nodes and L~4./H_2L~(2-) ligands as planar 4-connected nodes, respectively. 1 and 3 exhibit blue emission originated from the ligand with the emission maximum at 384 nm, while 2 shows intense characteristic red emission of Eu~(3+) ions and weak ligand-centered emission. Moreover, 2 has fluorescent quenching response towards the aromatic nitro compounds, especially for the 3,4-dinitrotoluene(3,4-DNT) with the linear Stern-Volmer relationship in the concentration range of 0–1 mM and the quenching constant(Ksv) of 2.084×10~3 M~(-1).     

Non-covalent Bonded 3D Supramolecular Architectures Based on Acid-base Adducts

Two novel acid-base adducts,[H_2L_1~(2+)](Hpbda)_2(1,L_1 = l,4-di(lH-imidazol-4-yl)benzene,H_2pbda = 1,4-benzenedicarboxylic acid) and[H_2L_2~(2+)](NO_3)_2(2,L_2 = l,4-di(l-carboxymethyl-imidazol-4-yl)benzene),have been prepared and characterized by single-crystal X-ray diffraction,IR spectroscopy and elemental analysis.Compound 1 crystallizes in monoclinic,space group P2_1/n with a = 5.3525(11),b = 9.1471(19),c = 19.314(4) ?,β = 92.342(3)°,V= 944.8(3) ?~3,Z = 2,C_(16)H_(16)N_6O_(10),M_r = 452.35,D_c = 1.590 g/cm~3,μ = 0.135 mm~(-1),S = 1.058,F(000) = 468,the final R = 0.0661 and wR = 0.1887 for 2298 observed reflections(I 2σ(I)).Compound 2 crystallizes in monoclinic,space group P2_1/c with a = 9.6923(10),b = 17.2950(17),c = 7.1880(7) ?,β =94.801(2)°,V= 1200.7(2) ?~3,Z = 2,C_(28)H_(22)N_4O_8,M_r = 542.50,D_c = 1.501 g/cm~3,μ = 0.112 mm~(-1),S= 1.060,F(000) = 564,the final R = 0.0394 and wR = 0.1017 for 2768 observed reflections(I 2σ(I)).In the title compounds,both of L_1 and L_2 ligands act as weak base to accept protons to exhibit diprotonated H_2L_1~(2+) and H_2L_2~(2+) form,which can effectively employ as hydrogen bonding donors to combine anion moieties to form binary adducts respectively.In the crystal packing diagram of two polymers,there exist extensive noncovalent interactions including charge-transfer interactions,C(N)-H…π and N-H…O,C-H…O,O-H…O hydrogen bonding interactions between co-crystal moieties which consolidate the structures of supramolecular polymers,thus generating three-dimensional(3D) frameworks.     

A Metal-organic Framework Containing Octanuclear Zn(Ⅱ) Clusters Constructed by 5-Methoxyisophthalate and Flexible Bis(imidazolyl) Ligand

The hydrothermal reaction of 5-methoxyisophthalic acid(MeO-H_2ip), 1,3-bis(2-methylimidazol-1?-yl)propane(bmip) and Zn(NO_3)_2·6H_2O in the presence of NaOCH_3 gave rise to a three-dimensional(3-D) metal-organic framework containing octanuclear Zn(II) units, [Zn_4(MeO-ip)_3(OH)_2(bmip)]n. Single-crystal X-ray diffraction analysis reveals that the complex crystallizes in the triclinic space group P1 with a = 11.348(3), b = 14.163(4), c = 15.088(4) ?, α = 108.537(2), β = 106.542(2), γ = 103.106(1)o, V = 2065.4(9) ?~3, Z = 2, M_r = 334.62, D_c = 1.740 g·cm~(-3), μ = 2.375 mm~(-1), S = 1.015, F(000) = 1096, the final R = 0.0272 and w R = 0.0715 for 8929 observed reflections(I 2σ(I)). The complex is thermally stable up to 370 oC, and exhibits photoluminescent emission at 450 nm on 350 nm excitation.     

Syntheses and Structures of a New Tetrazylphosphonate Ligand and the Coordination Polymer Based on Zn~(Ⅱ)

A novel tetrazylphosphonate ligand, namely ethyl 4-(2-ethyl-2H-1,2,3,4-tetrazol-5-yl) benzylphosphonate(Et-L), was designed and successfully achieved from p-cyano benzyl chloride, based on which a zinc coordination polymer(1) with a 2D layer structure has been hydrothermally synthesized and structurally characterized by elemental analysis, IR, TGA and X-ray single-crystal diffraction. The colorless block crystals of H_2L·H_2O were also obtained under the same hydrothermal conditions, which belongs to monoclinic system, space group P2_1/c with a = 13.3141(7), b = 5.1650(3), c = 21.9839(18) ?, β = 115.307(5)°, V = 1366.69(15) ?~3, Z = 4, D_c = 1.391 mg/cm~(-3), Mr = 349.58, F(000) = 600, R = 0.0748 and wR = 0.1917 for 2392 observed reflections(I 2σ(I)). The colorless block crystals of complex 1([Zn(L)(H_2O)]_n) also belong to monoclinic system, space group P2_1/c with a = 22.7464(10), b = 6.0430(3), c = 9.7704(4) ?, β = 92.525(4)°, V = 1341.70(10) ?~3, Z = 4, D_c = 1.731 mg/cm_(-3), M_r = 349.58, F(000) = 712, R = 0.0596 and wR = 0.1688 for 2357 observed reflections(I 2σ(I)). Only the oxygen atoms of phosphonic group are coordinated with the metal zinc probably because the hydrogen atom of tetrazole has been substituted by ethyl group. Photoluminescence properties of the complex are also investigated.