Syntheses, Structures and Magnetic Properties of Two Co(II) Coordination Polymers with 2,5-Pyridine Dicarboxylic Acid

The hydro(solvo)thermal reactions of cobalt powder or its chloride with 2,5- pyridine dicarboxylic acid (H2PYDC) yielded two new complexes: [Co(II)2(PYDC)2(H2O)2- (H2O)4]n 1 and {Co(II)[NH2(CH3)2]2(PYDC)2}n 2. It is observed that the reactive solvents result in different connectivity modes of ligand and diverse dimensional extension of crystal structures. The correlation between structure and magnetic property will be discussed in this paper. Crystal data for 1: space group P1, a = 7.0419(17), b = 8.937(2), c = 9.6182(19) ?, α = 91.532(4), β = 99.869(10), γ = 107.889(11)o, V = 565.5(2) ?3, Z = 1, Dc = 1.845 g/cm3, μ = 1.56 mm-1, F(000) = 322 , R = 0.0505 and wR = 0.1580; and those for 2: space group C2/c, a = 14.9075(6), b = 8.2523(3), c = 16.9643(2) ?, β = 100.982(2)o, V = 2048.75(11) ?3, Z = 4, Dc = 1.560 g/cm3, μ = 0.892 mm-1, F(000) = 996, R = 0.0443 and wR = 0.1134.

Separation Behavior of U(VI) and Th(IV) on a Mixed Ion Exchange Column Using 2,6-Pyridine Dicarboxylic Acid as a Complexing Agent and Determination of Trace Level Thorium in Uranium Matrix Employing High Performance Ion Chromatography

Retention behavior of U(VI) and Th(IV) as their 2, 6-pyridine dicarboxylic acid (PDCA) complexes on reversed phase and ion exchange (cation, anion and mixed ion exchange) columns was studied and based on the results, a simple ion chromatography method for the determination of trace level thorium in uranium oxide using 0.075mM 2, 6-pyridine dicarboxylic acid (PDCA) and 1M KNO3 in 1.2M HNO3 as eluent (flow rate 1 mL/min)was proposed. The advantage of the developed method is that the separation of uranium matrix is not required prior to the ion chromatographic determination of trace Th. Separation was carried out on a mixed ion exchange stationary phase and a 10?4 M arsenazo (III) solution was used as post column reagent for detecting the separated metal ions. The separation of Th from uranium using PDCA in the present investigation is attributed through cation exchange mechanism. A calibration plot was constructed by following the standard addition method over the concentration range of 0.25 to 10 ppm of Th in the presence of uranium matrix, which resulted in a linear regression coefficient of 0.9978. The precision of the method was better than 5% and the LOD for Th was found to be 0.1ppm (S/N=3). The method has been validated by comparing the results with the results obtained from ICP-MS analysis where the This separated from the uranium matrix. The proposed method is simple, rapid, accurate and cost effective compared to techniques like ICP-MS or ICP-AES and is suitable for the routine kind of analysis.

Synthesis of 2,6-pyridine Dimethyl Formate under Microwave Irradiation

An efficient synthesis of 2,6-pyridine dimethyl formate happened under the microwave irradiation is proposed. It is noteworthy that some factors influence the product yield such as time, temperature, ratio of reactants, and acidity which were discussed. The optimized quantity of 2,6-pyridine dimethyl acid is 10 mmol and methanol is 25 mmol. The yield is up to 95%-96% when using 2 mL 30% sulfuric acid. All products have been characterized by IR and 1H NMR.

Synthesis, Crystal Structure and Properties of a New Zn(II) Coordination Polymer Constructed from 2,3-Pyridine Dicarboxylic Acid and 1,1′-(1,4-Butanediyl)bis(imidazole)

A new coordination polymer, namely [Zn（pdc）（bbi）]n {H2 pdc = 2,3-pyridine dicar- boxylic acid, bbi = 1,1-（1,4-butanediyl）bis（imidazole）}, has been prepared under hydrothermal conditions and characterized by elemental analysis, IR, and single-crystal X-ray diffraction. It crystallizes in monoclinic, space group P21 /n with a = 8.436（3）, b = 16.988（5）, c = 12.106（4）, β = 92.204（5）°, V = 1733.6（9）3, Z = 4, C17 H17 N5 O4 Zn, Mr = 420.73, Dc = 1.612 g/cm3, F（000） = 864, μ（MoKa） = 0.452 mm-1, the R = 0.0672 and wR = 0.1645. In the mononuclear complex, each Zn（II） is five-coordinated by one carboxylate O and one pyridyl N atoms from one pdc anion, one carboxylate O atom from another pdc anion, and two N atoms from two bib ligands. The Zn（II） ions are connected by pdc ligands to form skeleton chains, and bbi ligands further link them to construct a 2D framework. The thermal and luminescence properties of the complex were also investigated.

Simple, Selective, and Sensitive Spectrophotometric Method for Determination of Trace Amounts of Nickel(Ⅱ), Copper (Ⅱ), Cobalt (Ⅱ), and Iron (Ⅲ) with a Novel Reagent 2-Pyridine Carboxaldehyde Isonicotinyl Hydrazone

A selective and sensitive reagent of 2-pyridine carboxaldehyde isonicotinyl hydrazone（2-PYAINH） was synthesized and studied for the spectrophotometric determination of nickel, copper, cobalt, and iron in detail. At a pH value of 7.0, 9,0, 9.0, and 8.0, respectively, which greatly increased the selectivity; nickel, copper, cobalt, and iron reacted with 2-PYAINH to form a 1：2 yellow-orange, 1：2 yellow-green, 1：2 yellow and 1：1 yellow complexes, with absorption peaks at 363, 352, 346, and 359 nm, respectively. Under the optimal conditions, Beer＇s law was obeyed over the ranges of 0.01-1.4, 0.01-1.5, 0.01-2.7, and 0.01-5.4 mg/L respectively. The apparent molar absorptivity and Sandell＇s sensitivities were 8.4×10^4, 5.2×10^4, 7.1×10^4, and 3.9×10^4 L·mol^-l·cm^-1, respectively, and 0.00069, 0.0012, 0.00078, and 0.0014 μg·cm2, respectively. The detection limits were found to be 0.001, 0.002, 0.003, and 0.01 mg/L, respectively. The detailed study of various interfering ions to make the method more sensitive was carried out and selective and several real samples were analyzed with satisfactory results.

The First Example of a Supramolecular Structure Containing [2-(1H-Pyrazol-3-yl)-pyridine] Complex and both α-and β-Octamolybdates

The title compound, [Ni（C8N3H7）3]4[Mo8O26]2·6H2O 1, has been synthesized from the reaction of 2-（1H-pyrazol-3-yl）-pyridine （L） with （NH4）2MoO4·2H2O and NiCl2·6H2O. Elemental analysis, IR, UV spectra and X-ray single-crystal diffraction were carried out to determine the composition and crystal structure of the compound. Crystal data： C96H96Mo16N36Ni4O58, Mr = 4451.97, monoclinic system, space group P21/n, a = 20.846（5）, b = 14.825（5）, c = 23.122（5） A ,β= 91.594（5）°, V = 7143（3）A^3, Z = 2, F（000） = 4344, Dc = 2.070 g/cm^3,μ = 1.968 mm^-1, R = 0.0452 and wR = 0.1056 for 17102 independent reflections （Rint = 0.0442） and 11074 observed reflections （I 〉 2σ（I））. Structural analysis indicates that two kinds of octamolybdates （[α-Mo8026]^4- and [β-Mo8026]^4-） co-exist in the compound. This is the first example of a supramolecular structure containing L complex as well as both α- and β-octamolybdate clusters.

Syntheses and Crystal Structures of [Ni(L)_2(NCS)_2] and [Co(L)_2(NCS)_2](L=Azobis(2-pyridine)

The ligand azobis(2-pyridine) L was used in the synthesis of two new organic-inorganic coordination complexes: [Ni(L)2(NCS)2] 1 and [Co(L)2(NCS)2] 2. Crystal data for 1: monoclinic, space group C2/c, a = 13.361(18), b = 10.731(15), c = 18.14(2) ? β = 109.86(2)? V = 2446(6) 3, Z = 4, Mr = 543.25, Dc = 1.410 g/cm3, μ = 0.993 mm-1, F(000) = 1064, T = 298(2) K, R = 0.0454 and wR = 0.1010 for 1288 observed reflections with I > 2s(I); and those for 2: monoclinic, space group C2/c, a = 13.35(2), b = 10.806(15), c = 18.06(2) , β = 110.34(2)? Z = 4, Mr = 543.49, Dc = 1.413 g/cm3, μ = 0.902 mm-1, F(000) = 1060, T = 298(2) K, R = 0.0699 and wR = 0.1354 for 728 observed reflections with I > 2s(I). Single-crystal X-ray diffraction studies revealed that 1 and 2 have similar structures, in which each Ni(II) or Co(II) cation is coordinated by two L ligands and two terminal thiocynates (NCS-).

An unexpected reaction of cyanothioacetamide:Novel preparation of pyrazolo[3,4-b]-pyridine derivatives under MWI

An unexpected multi-component reaction of cyanothioacetarnide with aldehyde and aminopyrazole under MWI was reported. Through this reaction, a series of pyrazolo[3,4-b]-pyridine derivatives was prepared in high yields via simple operational procedure.

Regioselective Synthesis of 2,6-Dimethyl-3,5-bis[（3-aryl-5- trifluoromethyl）-isoxazol-4-carbonyl]-pyridine Derivatives

Ethyl 4,4,4-trifluoro-3-oxo-butyrate reacted with 2,6-dimethyl-3,5-diacetyl-pyridine 1 in the presence of NaOC2H5 at 0 ℃ to give 2,6-dimethyl-3,5-bis（4,4,4-trifluoro-1,3-oxo-butyl）-pyridine （2a） in good yield. Cyclization reaction of 2a and aryl imidoyl chlorides 5a--5i, obtained from chlorination of aryl oximes with N-chlorosuccimide, afforded 2,6-dimethyl-3,5-bis[（3-aryl-5-trifluoromethyl）-isoxazol-4-carbonyl]-pyridine derivatives 6a=6i.

Colorimetric and electrochemical Pb^(2+) detection by imine-bridged tetrathiafulvalene-pyridine derivatives

Imine-bridged TTF-π-pyridine derivatives, 2NTTF, 3NTTF and 4NTTF, were synthesized and the cation-binding study was performed. It is noted that with the addition of the micromolar concentration of Pb2+ to the solution, these compounds display remarkable changes in solution color, 1H NMR spectra and electrochemical properties. The nitrogen atom of the imine-bridge in 2NTTF not only serves as a π-conjugated spacer but also participates in the sensing and coordinating properties.

Synthesis and Crystal Structure of a Cu(Ⅱ) Coordination Polymer: [Cu(L)(1,10-phen)]_n

A new complex [Cu（L）（1,10-phen）]n （1, L = N-3-pyridine sulfonyl amino acid） has been synthesized and characterized by IR, elemental analysis and X-ray diffraction analysis, and its crystal belongs to monoclinic, space group P2Jc with a = 11.481 （2）, b = 1 8.094（4）, c = 8.5198（17） ]°, β= 102.26（3）°, V = 1729.5（6） ,/k3, Z = 4, Dc = 1.759 g/cm3, F（000） = 932, p = 1.422 mm-1, R = 0.0368 and wR = 0.0893. In 1, the Cu（ll） ion adopts a slightly distorted five-coordinated square pyramidal geometry. The L2- ligand adopts O of the carboxyl bridging adjacent Cu（Ⅱ）units to form an infinite chain structure along the c axis. Also, π-π stacking interactions between the adjacent chains expanded the 1-D structures into a 3-D supramolecular structure.

Asymmetric Sequential Aza-Diels-Alder and O-Michael Addition： Efficient Construction of Chiral Hydropyrano[2,3-b]pyridines

An asymmetric aza-Diels-Alder and O-Michael addition sequence has been developed to construct chiral hy- dropyrano[2,3-b]pyridine derivatives with good yields and excellent stereoselectivity, by starting with N-Ts-l-aza- 1,3-butadienes and aliphatic aldehydes tethered to an α,β-unsaturated ketone motif. A tandem O-Michael addition reaction was completed via acid catalysis.