Hydrothermal synthesis and structure characterization of two six-connected metal–organic frameworks based on the mixed ligands

Two metal–organic frameworks, namely, [Ni₂(BIMB)₂(ndd)₂·H₂O]_n (1) and [Zn₃(ndd)_2.5(μ₃-OH)(1,3-dpp)]_n (2) (H₂ndd = 2,2′-(naphthalene-1,5-diylbis(oxy))diacetic acid, BIMB = 1,4-bis[(1H-imidazol-1-ly)methyl]benzene, 1,3-dpp = 1,3-di(pyridin-4-yl)propane) have been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction and thermogravimetric analysis. Compound 1 presents a two-dimensional network with point symbol of (3⁶·4⁶·5³)-hxl topology. Moreover, compound 2 displays a novel 2-fold interpenetrated structure with the point symbol of (4¹²·6³)-pcu topology based on the hexanuclear [Zn₆(CO₂)₁₀(N)₄] unit as a six-connected node. Meanwhile, compound 2 shows good fluorescence property in the solid state at room temperature.     

Luminescent nanoscale metal–organic frameworks for chemical sensing

Metal–organic frameworks(MOFs) are a fascinating class of crystalline materials constructed from selfassembly of metal cations/clusters and organic ligands. Both metal and organic components can be used to generate luminescence, and can further interact via antenna effect to increase the quantum yield,providing a versatile platform for chemical sensing based on luminescence emission. Moreover, MOFs can be miniaturized to nanometer scale to form nano-MOF(NMOF) materials, which exhibit many advantages over conventional bulk MOFs in terms of the facile tailorability of compositions, sizes and morphologies, the high dispersity in a wide variety of medium, and the intrinsic biocompatibility. This review will detail the development of NMOF materials as chemical sensors, including the synthetic methodologies for designing NMOF sensory materials, their luminescent properties and potential sensing applications.     

Inorganic–organic hybrids assembled by flexible multidentate linker: design,structure and luminescence

Transition Metal Chemistry - Three coordination complexes, [Cu(L1)(2,2–bipy)]2n·3nH2O (1), [Cu(L1)(2,2–bipy)2]·xH2O (2: x = 3.5 and 3: x?=?5), were synthesized by...     

Hydrothermal syntheses,structures, and properties of four metal–organic coordination polymers assembled from V-shaped tetracarboxylate ligands and N-donor ancillary ligands

A series of four metal–organic frameworks, namely, [Cu(sdpa)_0.5(2,2′-bpy)]·H₂O (1), [Zn₂(sdpa)(2,2′-bpy)₂(H₂O)₂]·3H₂O (2), [Zn₂(sdpa)(4,4′-bpy)]·3H₂O (3), [Cd₂(sdpa)(4,4′-bpy)_1.5(H₂O)₂](4), have been hydro(solvo)thermally synthesized through the reaction of 2,3,2′,3′-sulfonyldiphthalic acid (H₄sdpa) with divalent copper, zinc and cadmium salts in the presence of ancillary nitrogen ligands (4,4′-bpy = 4,4′-bipyridine, 2,2′-bpy = 2,2′-bipyridine) and structurally characterized by elemental analysis, IR and X-ray diffraction. Both complex 1 and 2 show metal–organic chain structure, and the adjacent chains are further linked by π?π and C–H?π interactions for 1 and hydrogen bonds and π?π interactions for 2 to form 3D supramolecular structure. In complex 3, two Zn1 and two Zn2 atoms appear alternately and are bridged by sdpa⁴⁻ anion ligands to form an infinite Zn-sdpa chain. Such chains are further linked together through 4,4′-bpy ligands in four orientations to form a robust 3D metal–organic network. In compound 4, a 3D Cd-sdpa metal–organic network is accomplished through sdpa⁴⁻ anion ligands, and further stabilized by 4,4′-bpy in six orientations. Their luminescence and thermal analysis have also been investigated.     

Synthesis,characterization and magnetic properties of supramolecular metal–organic complexes constructed from flexible–rigid mixed ligands

Two new supramolecular metal–organic complexes have been synthesized under hydrothermal conditions. Complex 1 exhibits a three-dimensional supramolecular network, constructed from [Co₂(H₃BPTC)₂(phen)₂] (H₄BPTC = 3,3′4,4′-benzophenone tetracarboxylate acid, phen = 1,10-phenanthroline) discrete units. Complex 2 similarly exhibits discrete [Cu₂(DPA)₂(bipy)₂(H₂O)₂] (DPA = 1,1′-biphenyl-2,2′-dicarboxylate acid, bipy = 2,2′-bipyridine) units, which are linked to form a three-dimensional supramolecular network through π–π interactions. It is interesting that during the synthesis of complex 1, the H₄BPTC ligands undergo partial decomposition to give 1,2,4-benzenetricarboxylate (H₃BTC) ligands, which react with Co to form [Co₃(BTC)₂]_n (3). Complex 3 shows a three-dimensional covalent network. The magnetic properties of complexes 1 and 2 have been studied.     

Selective adsorption of potassium and rubidium by metal–organic frameworks supported supramolecular materials

Journal of Radioanalytical and Nuclear Chemistry - A new MOFs-based adsorbent UiO-66@iPCC5 was prepared by hybridization of 25,27-bis(iso-propoxyl)-calix[4]arene-26,28-crown-5 (iPCC5) into the...     

Self‐assembled diols: synthesis,structure and dielectric studies

In single‐, double‐, and triple‐chain amphiphilic diols the CONH group was replaced by CON(CH₃) in order to reduce the number of proton donor groups available for intermolecular hydrogen bonding. The resulting three new liquid crystalline diols were studied by DSC, X‐ray and dielectric measurements, and show the mesophases SmA, Col_H2 or Cub_I2, depending on the number of decyloxy groups in the hydrophobic part of the molecule. The process of self‐assembly to different liquid crystalline phases is well seen in the dielectric spectrum and details of this process are discussed together with results from the X‐ray measurements. All the compounds show a high frequency dielectric absorption caused by the dynamics of the network of hydrogen bonds. An additional low frequency process related to the internal dynamics of the columns is seen only in the columnar phase.     

Hydrogen physisorption in metal–organic frameworks: concepts and quantum chemical calculations

Storage of hydrogen by physisorption in metal–organic frameworks is reviewed from the perspective of quantum chemistry. Concepts regarding the interaction of hydrogen with metals are revised and the specific features of metal–organic frameworks are explained. The influence of the type of inorganic cluster and hydrogen loading and its relation to hydrogen storage are analysed. Heats of hydrogen adsorption in previous studies are critically discussed and estimations are made regarding the adsorption strength needed for storage applications and how to approach commercial targets.     

Syntheses,crystal structures,and characterization of three metal–organic complexes with 2,2′-biphenyldicarboxylic acid and phenanthroline ligands

Three complexes constructed with 2,2′-biphenyldicarboxylic acid, multidentate nitrogen donors, and metal salts, {[Cd(2,2′-dpdc)(tppp)(H₂O)]₂?·?2H₂O} _n (1), {[Pb(2,2′-dpdc)(pyphen)]₂} _n (2), and {[Pb(2,2′-dpdc)(dppz)]} _n (3) (H₂dpdc = 2,2′-diphenyldicarboxylic acid; tppp = 4-(1H-1,3,7,8-tetraazacyclopenta[l]phenanthren-2-yl)phenol; pyphen?=?pyrazino[2,3-f]-[1,10]phenanthroline; and dppz = dipyrido[3,2-a:2′,3′-c]phenazine), are synthesized under hydrothermal conditions. These complexes are characterized by single-crystal X-ray diffraction, elemental analysis, IR, TGA, and photoluminescence. In 1, two 2,2′-dpdc ions bridge two Cd(II) ions to form an isolated cluster with Cd?···?Cd distance of 5.023(4)?Å. These clusters are further linked by intermolecular hydrogen bonds, yielding a 2-D supramolecular structure. Complex 2 contains two crystallographically independent Pb(II) ions in the asymmetric unit. Pb1 ions are bridged by 2,2′-dpdc anions to form a chain along the x-axis. Two Pb2 ions are coordinated by two 2,2′-dpdc anions and two pyphen ligands to form a cluster. These clusters are linked by π–π interactions to yield a 1-D supramolecular chain along the y-axis. In 3, neighboring Pb(II) atoms are bridged by 2,2′-dpdc anions to form a 1-D chain structure. Further, the chains are linked into a 3-D supramolecular network through aromatic π–π interactions.     

A three-dimensional highly stable cobalt(II) metal–organic framework based on terephthalic acid: synthesis, crystal structure, thermal and physical properties

A metal?Corganic framework complex, [Co(??₃?Ctp)(??₂?pyz)] _n , where H₂tp?=?1,4-benzenedicarboxylic acid (terephthalic acid) and pyz?=?pyrazine, has been synthesized under hydrothermal conditions and characterized by physico-chemical and spectroscopic methods, thermogravimetric analysis and single-crystal X-ray diffraction. Each Co(II) center is surrounded by four carboxylate oxygen atoms from three tp ligands and two nitrogen atoms from two pyrazine ligands, giving a distorted octahedral geometry. The entire framework is made up of two-dimensional sheets of dicobalt ions linked via terephthalate ligands to form rectangles. The sheets are then linked into each other via the axial pyrazine ligands, forming an interlocked 3-D network, which is finally arranged as an ABAB interconnected pattern. Photoluminescence measurements for the polymer in the solid state show an emission at 414?nm, which suggests this complex as a potential blue-light material. The electrochemical behavior of a modified carbon paste electrode prepared from the complex has been studied by cyclic voltammetry, indicating quasi-reversible redox behavior.     

A 2D cadmium metal–organic framework: Synthesis,structure and luminescence sensing for chromate,permanganate, cupric,silver and ferric

A multi-responsive Cd metal–organic framework {[Cd (ttpe)(H₂O)(ip)]•4H₂O•DMAC}_n ( 1•4H ₂ O•DMAC ) was synthesized using hydrothermal method (ttpe = 1,1,2,2-tetra(4-(1H-1,2,4-triazol-1-yl)phenyl)ethylene, ip = isophthalate, DMAC = N,N-dimethylacetamide), and characterized. 1 exhibits a 2D (4,4) network. The luminescent sensing experimrnts showed that 1•4H ₂ O•DMAC as a new MOF luminescent sensor can detect Cr₂O₇²⁻, CrO₄²⁻, MnO₄⁻, Cu²⁺, Ag⁺ and Fe³⁺ in aqueous solution with simultaneously high efficiency and high sensitivity. The quenching constants K_sv for Cr₂O₇²⁻, CrO₄²⁻, MnO₄⁻, Cu²⁺, Ag⁺ and Fe³⁺ are 4.231 × 10⁴ M⁻¹, 2.471 × 10⁴ M⁻¹, 6.459 × 10³ M⁻¹, 7.617 × 10³ M⁻¹, 1.563 × 10⁴ M⁻¹ and 3.574 × 10⁴ M⁻¹, respectively. The detection limits are 0.094 μM for Cr₂O₇²⁻, 0.108 μM for CrO₄^{2 −} , 0.346 μM for MnO₄⁻, 0.302 μM for Cu²⁺, 0.221 μM for Ag ⁺ , and 0.100 μM for Fe³⁺. 1•4H ₂ O•DMAC exhibits high photocatalytic efficiency for degradation of methylene blue under visible light irradiation.     

Ultrasonic synthesis,crystal structure,luminescent, and magnetic properties of a new metal–organic complex based on Ce(IV)–Sr(II)

Research on Chemical Intermediates - This paper presents the sonochemical synthesis of a new hetero-metallic inorganic complex, formulated as [(Sr(OH2)5Ce(dipic)3Sr(OH2)6][Ce(dipic)3]·6H2O...     

Syntheses,crystal structures,and magnetic properties of three one-dimensional metal–nitroxide complexes linked by 1,4-cyclohexanedicarboxylate ligands

Three one-dimensional metal–nitroxide complexes [Cu(NIT4Py)₂(1,4-chdc)] _n (1), {[Cu(IM4Py)₂(1,4-chdc)(H₂O)]·H₂O} _n (2) and {[Zn(IM4Py)₂(1,4-chdc)(H₂O)₂]·H₂O} _n (3) (NIT4Py = 2-(4′-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, IM4Py = 2-(4′-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl and 1,4-chdc = 1,4-cyclohexanedicarboxylate anion) have been synthesized and characterized structurally as well as magnetically. All three complexes crystallize in neutral one-dimensional chains in which the nitroxide–metal–nitroxide units are linked by linear 1,4-cyclohexanedicarboxylate anions. The 1,4-chdc ligands only present the e,e-trans-configuration in these complexes, although there are both cis- and trans-isomers in the free ligand. Magnetic measurements show that complexes 1 and 2 both exhibit weak antiferromagnetic interactions between the copper atoms and nitroxide radicals.     

Design and development of several polymeric metal–organic frameworks,spectral characterization,and their antimicrobial activity

Coordination polymers were obtained by the reaction of metal acetates, M(CH₃COO)₂·xH₂O {where M = Mn(II), Co(II), Ni(II) and Cu(II)} with AFP ligand (AFP = 5,5'-(piperazine-1,4-diylbis(methylene))bis(2-aminobenzoic acid). The AFP ligand was prepared by the one-pot, two-step reaction of formaldehyde, 2-aminobenzoic acid, and piperazine. Structural and spectroscopic properties have been studied by elemental, spectral (FT-IR, ¹H NMR, ¹³C NMR, and UV–vis), and thermogravimetric analysis. UV–vis spectra and magnetic moment values indicate that Mn(II), Co(II), and Ni(II) polymer–metal complexes are octahedral, while Cu(II) and Zn(II) polymer–metal complexes are distorted octahedral and tetrahedral, respectively. The analytical data confirmed that the coordination polymers of Mn(II), Co(II), Ni(II), and Cu(II) are coordinated with two water molecules, which are further supported by infrared spectra and thermogravimetric analysis data. The prepared polymer–metal complexes showed good antibacterial activities against all tested microorganisms; however, the AFP ligand was also found to be effective, but relatively less than their polymer–metal complexes. Along with antibacterial activity, all the polymer–metal complexes exhibit significant antifungal activity against most of the tested fungal strains. The results of antimicrobial activity reveals that the AFP–Cu(II) showed the highest antibacterial and antifungal activity than other polymer–metal complexes.