A blue fluorescent Cd(II) coordination polymer with 3,5-diaminobenzoic acid ligand: synthesis, crystal structure and fluorescent property

Under hydrothermal conditions, the reaction of 3,5-diaminobenzoic acid (HDABC) with Cd(ClO₄)₂ ∼ 6H₂O affords a novel 2D network, {[Cd(DABC)₂][Cd(DABC)₂(H₂O)₂]}_n (1), which, represents the first example of 2D neutral polymeric material containing DABC ligand with strong blue fluorescent emission in the solid state.     

Supramolecular architectures of cadmium(II) built of 2,2′-biimmidazole and bifunctional carboxylates: Syntheses, crystal structure and properties

A series of four new supramolecular complexes of cadmium(II), {[CdBr(H₂biim)(PyCO₂)(H₂O)](H₂O)}_∞ (1) (H₂biim = 2,2′-biimidazole, PyCO₂ = isonicotinate), [Cd(H₂biim)₂(HBDC)₂] (2) (H₂BDC = terephthalic acid), [Cd(H₂biim)₂(H₂O)₂](BDC) (3) and [Cd(H₂biim)₂(H₂O)₂](PyCO₂)₂ · 4H₂O (4) have been prepared and characterized by X-ray crystallography, IR, fluorescence spectra and thermogravimetric analysis. Compound 1 exhibits an infinite chain-like structure through bridging isonicotinate. Strong interchain hydrogen bonds between isonicotinate and H₂biim result in the robust 2-D sheet structure, responsible for the insolubility. The similar hydrogen bonds between H₂biim and the coordinated 1,4-bdc and complementary hydrogen bonds between monoprotonated bdc are responsible for the robust 2-D layered structure of 2 that is insoluble in aqueous solution. 1,4-Bdc becomes uncoordinated in the soluble complex 3, although it has hydrogen bonded 2-D structure as well.     

Three zinc-organic frameworks based on 1,4-benzenebis(thioacetic acid): Syntheses, crystal structures, and luminescent properties

A new flexible aromatic multithiocarboxylate ligand: 1,4-benzenebis(thioacetic acid) (H₂L), was synthesized and introduced to construct three interesting metal-organic frameworks (MOFs) with the photoluminescent properties. Three MOFs were characterized by the elemental analysis, infrared (IR) spectrum, and single crystal X-ray diffraction. [Zn₃L₃(2,2′-bipy)₂]_n (1) is a two-dimensional (2D) layered architecture that consists of the linear trinuclear units of Zn atoms. [ZnL(2,2′-bipy)(H₂O)]_n·0.7nH₂O (2) is a one-dimensional (1D) helical chain, which further forms a 2D structure with 30-membered ring with a size of 7.64 × 15.53 Å via O−H···O hydrogen bonds. [ZnL(phen)(H₂O)]_n·0.35nH₂O (3) presents a 2D supramolecular network through the O−H···O interactions. Their thermal and photoluminescent properties in solid state were given.     

2D network coordination polymers of lanthanide with N-(2-pyridylmethyl)iminodiacetic acid: Hydrothermal syntheses, crystal structures and luminescent properties

Six lanthanide two-dimensional network coordination polymers with the general formula of [Ln(pmida)(NO₃)(H₂O)]_n, where Ln = La (1), Nd (2), Sm (3), Gd (4), Dy (5), Er (6) and pmida²⁻ = N-(2-pyridylmethyl)iminodiacetate, have been synthesized by hydrothermal process and characterized by elemental analysis, Infrared spectroscopy, thermogravimetric analysis and single-crystal X-ray diffraction. All crystals are isostructural and crystallize in the monoclinic space group P2₁/a. The lanthanide(III) ion is nine-coordinated in a geometry of distorted tricapped trigonal prism by two N atoms and two O atoms from one pmida²⁻ ligand, two bridging carboxylate O atoms from other two pmida²⁻ ligands, two O atoms of a bidentate chelating nitrate and a O atom of a coordinated water molecule. The luminescent properties of [Sm(pmida)(NO₃)(H₂O)]_n (3) and [Dy(pmida)(NO₃)(H₂O)]_n (5) were investigated.     

A novel one-dimensional chain-like structure based on sandwich-type tungstoantimonate and cadmium(II)

A novel cadmium-substituted tungstoantimonate [Sb₂W₂₁Cd(OH)₂O₇₃]¹⁴⁻ (1), has been synthesized in aqueous solution and characterized by IR, elemental analysis, TGA and cyclic voltammetry (CV). Single-crystal X-ray analysis was carried out on K_4.5Na_9.5[Sb₂W₂₁Cd(OH)₂O₇₃] · 31H₂O (1a). Polyanion 1 consists of two Cd(W) ions linked to a [Sb₂W₂₀O₇₀]¹⁴⁻ fragment via Cd-O(W) bonds leading to a sandwich-type structure. Interestingly, the polyanion [Sb₂W₂₁Cd(OH)₂O₇₃]¹⁴⁻ (1) as basic building unit is assembled into a one-dimensional (1D) chain-like structure by Cd and W atoms sharing the same site with the 50% occupations, respectively. The electrochemical behavior of 1 was investigated in buffer solution (pH 3.0) by CV. In the potential range between −0.75 and 0.2 V, the compound 1 exhibits the successive redox processes of the addenda atoms (W). The electrocatalytic experiments of the compound show that this compound has good electrocatalytic activity towards the reduction of H₂O₂.     

6-羟基烟酸3-单加氧酶(NicC)催化反应机理研究

恶臭假单胞菌(Pseudomonas putida)KT2440中的6-羟基烟酸(6HNA)3-单加氧酶(NicC)是烟酸代谢过程中的关键酶。NicC通过在吡啶环上加羟基对吡啶环进行活化,从而使吡啶环可在双加氧酶催化下开环,最终被完全降解。通过去除NicC的N端稀有密码子增加了NicC的表达量,进一步利用Ni-Sepharose重力柱对NicC进行了纯化。通过实验发现,NicC的最适反应温度为30～40℃,最适反应pH为8.0。Cd~(2+)对NicC的酶活有明显的抑制作用。当NADH的浓度为0.25mmol/L时,底物6HNA所对应的NicC的最大酶活为14.1U/mg,K_m值为51.8μmol/L;当6HNA的浓度为0.25mmol/L时,底物NADH所对应的NicC的最大酶活为10.79U/mg,K_m值为15.0μmol/L。通过HPLC和LC-MS分析表明,NicC可以在NADH和氧气的参与下催化6HNA转化生成2,5-二羟基吡啶(2,5-DHP)和甲酸,还可以将对羟基苯甲酸转化生成对苯二酚。同位素标记实验表明,产物2,5-DHP中的氧原子来源于参与反应的氧气。为研究吡啶类化合物微生物代谢提供了理论基础。     

In situ hydrothermal syntheses, crystal structures and luminescent properties of two novel zinc(II) coordination polymers based on tetrapyridyl ligand

Two novel Zn(II) coordination polymers, [Zn(2-pytpy)(fum)]_n·nH₂O (1) and [Zn₆(4-pytpy)₃(mal)₄]_n·5n(H₂O) (2), (2-pytpy = 4′-(4-pyridyl)-2,2′:6′,2″-terpyridine, 4-pytpy = 4′-(4-pyridyl)-4,2′:6′,4″-terpyridine, H₂fum = fumaric acid and H₂mal = malic acid) have been hydrothermally synthesized and structurally characterized. Notably, in situ ligand reactions occur in the formation of complexes 1 and 2, in which maleic acid is converted into fumaric acid and malic acid, respectively. Complex 1 is a 1D infinite chain structure, which is extended into a supramolecular layer by intermolecular π…π stacking interactions. Complex 2 is a 3D network structure, in which the bidentate-bridging 4-pytpy ligands link the layers based on the tetranuclear Zn(II) subunits to form the (4,10)-connected network. The luminescent properties of 1 and 2 have been investigated with emission spectra and UV-Vis diffuse reflectance spectra in the solid state. Additionally, these two complexes possess great thermal stabilities.     

Syntheses, structures and properties of copper(II) and cobalt(II) metal-organic frameworks based on R-isophthalate (R = -CH3 or -C(CH3)3) and 1,1′-(1,4-butanediyl)bis(imidazole) ligands

Three new complexes [Cu₂(mip)₂(bbi)]_n (1), {[Cu₂(tbip)₂(bbi)₂(H₂O)]·2H₂O}_n (2) and {[Co₂(tbip)₂(bbi)₂]·2H₂O}_n (3), were prepared through hydrothermal reactions of Cu(II) and Co(II) acetate with H₂mip or H₂tbip (H₂mip = 5-methyl isophthalic acid and H₂tbip = 5-tert-butyl isophthalic acid) and the flexible ligand bbi (bbi = 1,1′-(1,4-butanediyl)bis(imidazole)). All these complexes were structurally characterized by elemental analysis, IR spectroscopy and X-ray single-crystal diffraction. Complex 1 exhibits a 3D network, which are constructed from 2D carboxylate layer and bbi pillar. Complex 2 possesses a 2D layer structure, and exists extensive hydrogen-bonding interactions, while complex 3 is constructed from 2D layers which consists of alternating left- and right-handed helical chains, and further assembled to form a 3D framework by hydrogen-bonding interactions. The thermal stabilities of the corresponding complexes have been briefly investigated. In addition, dominant antiferromagnetic coupling was observed in complex 1.     

Bioelectrochemical transformation of nicotinic acid into 6-hydroxynicotinic acid on Pseudomonas fluorescens TN5-immobilized column electrolytic flow system

Pseudomonas fluorescens TN5 catalyzes the hydroxylation of nicotinic acid (NA) into 6-hydroxynicotinic acid (6HNA), an important compound as a starting material for the synthesis of a new type of pesticides. Under aerobic conditions, however, 6HNA is metabolized in the P. fluorescens cells. The use of Fe(CN)₆³⁻ as an extracellular electron acceptor enhances the biotransformation of NA into 6HNA and completely suppresses the subsequent oxidation of 6HNA. The function of the P. fluorescens cell was combined with the electrode process by immobilizing the P. fluorescens cells on the carbon fiber electrode surface in the column, where Fe(CN)₆³⁻ was used as an electron transfer mediator. Continuous-flow electrolysis of NA in the presence of Fe(CN)₆³⁻ at the P. fluorescens-immobilized column electrode realized the accelerated and complete transformation of NA into 6HNA without any by-product.     

pH responsive luminescent switches of ruthenium(II) complexes containing two imidazole groups: Synthesis, spectroscopy, electrochemistry and theoretical calculations

A series of new mononuclear polypyridyl ruthenium(II) complexes containing two imidazole groups have been synthesized and characterized by ¹H NMR, ES-MS, FAB-MS, IR spectra and elemental analysis. Their electrochemistry and spectroscopic properties including UV-Vis absorption, steady-state and time-resolved emission have been studied using both experimental methods and theoretical calculations. These complexes have been found to be sensitive luminescent pH switches, as their absorption and emission spectra respond to the solutions pH disturbances with extraordinary sensitivity, through the protonation and deprotonation of the imidazole groups. DFT calculations have been carried out to reveal the exact protonation and deprotonation route. The ground-state and excited-state ionization constants (pK_a and ) of each acid-base equilibrium have also been calculated according to the absorbance and emission data under different pH.     

Synthesis and structural characterization of cadmium(II) complexes with 2-(2-pyridyl)imino-N-(2-thiazolin-2-yl)thiazolidine (PyTT)

We have carried out the synthesis of the cadmium coordination compounds [Cd(NO₃)₂(PyTT)(H₂O)] (1) and [CdCl₂{(μ-Cl)₂CdCl(μ-Cl)(μ-PyTT)Cd}₂]_n (2), together with their structural determination by means of X-ray diffraction. The compounds were also characterized through elemental analysis and infrared spectroscopy. The first complex presents a distorted pentagonal bipyramidal geometry with the axial positions occupied by one oxygen atom from a water molecule and a second one from a nitrate ion which acts as a monodentate ligand, whereas the equatorial plane contains three nitrogen atoms from the organic moiety and two oxygen atoms coming from the other nitrate group, which is bidentate. The structure of the second complex consists of parallel sheets linked by van der Waals forces, each one made up of structural units [CdCl₂{(μ-Cl)₂CdCl(μ-Cl)(μ-PyTT)Cd}₂], which possesses two PyTT ligands, 10 bridging chloro ligands and 5 cadmium(II) centres belonging to three environment types: octahedral CdN₂Cl₄, octahedral CdCl₆, on which a centre of symmetry is located, and tetrahedral CdNCl₃, present in a 2:1:2 ratio.     

3D supramolecular network assembly and thermal decomposition of new copper(II) complexes with pyrazine-2,6-dicarboxylic acid

Four new Cu(II) complexes [Cu(pzda)(2,2′-bpy)(H₂O)] · 2.5H₂O (1), [Cu(pzda)(phen)(H₂O)] · H₂O (2), [Cu(pzda)(4,4′-bpy)] · H₂O (3) and [Cu(pzda)(bpe)_0.5(H₂O)] (4) were synthesized by hydrothermal reactions of copper salt (acetate or sulphate) with pyrazine-2,6-dicarboxylic acid (H₂pzda), and 2,2′-bipyridine (2,2′-bpy), 1,10-phenanthroline (phen), 4,4′-bipyridine (4,4′-bpy) or 1,2-bis(4-pyridyl)-ethane (bpe), respectively. For 1 and 2, they are both monomeric entities which are further assembled into 3D supramolecular networks by hydrogen bonds and π-π stacking interactions. Complex 3 has a 2D metal-organic framework which is connected into 3D supramolecular network by hydrogen bonds. However, for 4, the bpe ligand bridges two Cu(II) ions into binuclear unit, and then the binuclear molecules are assembled into 3D supramolecular network by hydrogen bonds between the coordination water molecule and the carboxylate oxygen atoms. The thermal decomposition mechanism of complexes 1 and 2 cooperated with powder XRD at different temperatures is discussed. The results reveal that once liberation of water molecules takes place the supramolecular network of 1 and 2 collapses.     

Double-bowed nanoscale decanuclear copper(II) assemblies based on tartaric acid

The tartaric acid (H₄L), serving as versatile tectons, link Cu^II atoms with three different bridging modes to form a unique double-bowed nanosized Cu₁₀-assembly, namely, [Cu^II₁₀(H₂L)₄(HL)₄]·(apy)₈·13H₂O (1) (apy = 2-aminopyridine). Single-crystal analysis reveals that the nano-cluster is composed of two bow-shaped pentameric subunits joined together by carboxyl O bridges, in which eight Cu^II atoms are in distorted octahedral site, while the other two Cu^II atoms display the square-pyramidal geometries. Interestingly, such decanuclear SUBs are connected by (12) H-bonding rings into a 3D α-Po network. Magnetic studies show an antiferromagnetic interaction between Cu^II centers.     

Synthesis and crystal structures of four pH-dependent Pb(II) and Cd(II) phosphonates based on a novel ligand, 3-phosphono-benzoic acid

Four metal phosphonate hybrid compounds, [Pb(Hpbc)] (1), [Pb₃(pbc)₂(H₂O)₂] (2), [Cd(H₂pbc)₂(H₂O)₂] (3) and [Cd_1.5(pbc)(H₂O)_1.5] · 0.5H₂O (4) (H₃pbc = 3-phosphono-benzoic acid) were successfully synthesized by the hydrothermal/solvothermal reaction of metal acetate and 3-phosphono-benzoic acid. Compounds 1-4 were pH-dependent products and characterized by elemental analysis, Fourier transform infrared (FT-IR) spectra and single-crystal X-ray diffraction studies. Compound 1 is a two-dimensional (2D) structure constructed by inorganic layer and organic pendant. With the increase of pH value, structure 2 shows 3D inorganic framework with distributing organic moieties in the channels. In 3, the Cd₂O₁₀ dimers are linked by alternating terminal and bridging ligands, resulting in 1D chain structure. Compound 4 is a 2D structure where the 1D inorganic chains are connected by the organic moieties of the ligands.     

Five-, seven-, and eight-coordinate Cd(II) coordination polymers built by anthranilic acid derivatives: Synthesis, structures and photoluminescence

Two novel Cd(II) coordination polymers, [(CH₃)₂NH₂]₂[Cd(cma)₂](H₂O) (1) and [Cd₃(bcma)₂(H₂O)](H₂O) (2) (H₂cma = N-(carboxymethyl)-anthranilic acid, H₃bcma = N,N′-bis-(carboxymethyl)-anthranilic acid), have been synthesized under hydrothermal conditions and characterized by X-ray single crystal analysis, IR spectra and TGA. Compound 1 possesses 1D double-stranded chain, which further packs into square channels. Compound 2 consists of a novel 3D framework, which not only possesses unique meniscus-like channels but also contains infinite helical chains. Compound 2 is the first example of Cd(II)-aminopolycarboxylate coordination polymers containing three crystallographically independent Cd(II) centres, in which Cd(1), Cd(2), and Cd(3) present distorted pentagonal bipyramidal, tetragonal antiprismatic, and trigonal bipyramidal coordination geometry, respectively. Both compounds display intense room temperature photoluminescence in the solid state.     

Syntheses, crystal structures and properties of Cd(II) and Co(II) complexes with 4,4′-dipyridylsulfide ligand

Two new coordination polymers [Cd(dps)₂Cl₂] (1) and [Co(dps)₂(H₂O)₂]·(abs)₂(H₂O)₂ (2) (dps = 4, 4′-dipyridylsulfide, Habs = 4-amino benzenesulfonic acid) have been synthesized under similar conditions and characterized by elemental analysis, fluorescence spectra and single crystal X-ray diffraction. Compound 1 displays a dps-bridged 2D puckered, grid-like layer, which is further linked by C-H?Cl hydrogen bonds to form a 3D supramolecular architecture. Compound 2 shows a dps-bridged double-stranded chain structure, which is extended by N-H?O and O-H?O hydrogen bonds generating a 3D network. Solid-state fluorescence results reveal that both complexes can emit strong emission bands, at 467 nm and 518 nm for 1 and 344 nm for 2, respectively. Magnetic measurements show that there are weak antiferromagnetic interactions between the adjacent Co(II) ions in 2.     

Supramolecular isomers of lanthanides(III): Synthesis, crystal structures and luminescent properties

Six lanthanide coordination polymers La₂(1,4-BDOA)₂(OX)(H₂O) (1), Ln₂(1,4-BDOA)₂(OX)(H₂O) [Ln = La (2); Ln = Pr (3); Ln = Sm (4); Ln = Eu (5); Ln = Tb (6)], [BDOA = benzene-1,4-dioxydiacetate; OX = oxalate] had been prepared under hydrothermal conditions, which were characterized by elemental analysis, infrared spectroscopy, thermogravimetric analysis, and single-crystal X-ray diffraction. Compounds 1-6 crystallize in a triclinic system, space group ; compounds 1 and 2 are true structural supramolecular isomers based on BDOA ligands constructed from different acid effects; compounds 2-5 are isostructural and exhibit new 3D 12-connected topological networks, which are the same as the topological structure of 6, while 1 shows another 3D 11-connected topological architecture. Furthermore, the luminescent properties of 5 and 6 were studied.     

Organic-inorganic hybrid materials constructed from Cu(II)-organonitrogen coordination complex cations and oxovanadium-arsonate subunits

The hydrothermal reactions of NH₄VO₃, Cu(NO₃)₂·H₂O or Cu(CH₃CO₂)₂·H₂O As₂O₅ and the appropriate organonitrogen ligand in the presence of HF as mineralizer yield a series of bimetallic oxides of the Cu/V/O/As family. The materials [Cu(bpy)(VO₂)(AsO₄)] (1) and [Cu(bpy)VO₂(OH)(AsO₄H)]·H₂O (2·H₂O) are one-dimensional (bpy = 2,2′-bipyridine). While phase 1 is constructed from chains decorated by {Cu(bpy)}²⁺ groups, compound 2 consists of {V₂O₄(OH)₂(AsO₄H)₂}²⁻ clusters linked through {Cu(bpy)}²⁺ subunits. In contrast, the structure of [Cu₂(bpyrm)(VO₂)₂(AsO₄)₂]·H₂O (3·H₂O) is three-dimensional, consisting of layers, linked through {Cu₂(bpyrm)}⁴⁺ rods (bpyrm = bipyrimidine).     

Supramolecular networks of hexanuclear cadmium (II): Synthesis, crystal structure and emission property

A new hexanuclear cadmium(II) complex of Cd₆(pyim)₄(Hpyim)₆(sal)₄ (Hpyim = 2-pyridylbenzimidazole, H₂sal = salicylic acid) (1) has been synthesized under hydrothermal condition and characterized by element analysis, FT-IR spectroscopy and luminescent analysis. X-ray crystallographic studies reveal that complex 1 displays a novel hexanuclear unit in which six cadmium ions are bridged by deprotonated salicylic and pyridylbenzimidazole ligands. In 1, the hexanuclear units are further assembled into a 3D supramolecular framework by hydrogen bonding, π-π and C−H?π stacking interactions. In the solid state, complex 1 shows blue photoluminescent property at room temperature.     

Hydrothermal syntheses, structural characterizations and magnetic properties of cobalt(II) and manganese(II) coordination polymeric complexes containing pyrazinecarboxylate ligand

Two novel coordination polymeric complexes [Co(pzca)₂(H₂O)]_n (1) and [Mn(pzca)₂]_n (2) (pzca=2-pyrazinecarboxylate) have been synthesized by hydrothermal reaction of M(CH₃COO)₂·4H₂O (M=Co, Mn) and 2-pyrazinecarboxylic acid. The complex 1 displays an infinite zigzag chain structure in which each cobalt(II) center was coordinated by three nitrogen and three oxygen atoms to generate a CoN₃O₃ octahedral geometry. The existence of hydrogen bond leads to the formation of the interpenetrating stacking structure. Complex 2 indicates a two-dimensional layer structure through the linkage of bridging oxygen atom of pzca ligand. Each Mn(II) center exhibits a distorted octahedral coordination environment with four oxygen atoms and two nitrogen atoms. The distances of adjacent Mn(II) atoms are 3.503 and 5.654 Å, respectively. The magnetic property analyses reveal that both complexes show weak antiferromagnetic exchange interactions between the metal centers.