Low-temperature heat capacities and standard molar enthalpy of formation of pyridine-2,6-dicarboxylic acid

This paper reports that the low-temperature heat capacities of pyridine-2,6-dicarboxylic acid were measured by a precision automatic calorimeter over a temperature range from 78 K to 380 K. A polynomial equation of heat capacities as a function of temperature was fitted by the least-squares method. Based on the fitted polynomial, the smoothed heat capacities and thermodynamic functions of the compound relative to the standard reference temperature 298.15 K were calculated and tabulated at intervals of 5 K. The constant-volume energy of combustion of the compound was determined by means of a precision rotating-bomb combustion calorimeter. The standard molar enthalpy of combustion of the compound was derived from the constant-volume energy of combustion. The standard molar enthalpy of formation of the compound was calculated from a combination of the datum of the standard molar enthalpy of combustion of the compound with other auxiliary thermodynamic quantities through a Hess thermochemical cycle.

Synthesis of 3 or 4-Substituted Pyridine-2, 6-Dicarboxylic Acid

Various 4-alkoxypyridine-2, 6-dicarboxylic acids were synthesized starting from 2, 6- lutidine. Through aldol condensation and Michael addition, various 4-arylpyridine-2, 6-dicarboxylic acids were synthesized starting from aromatic aldehydes and 2-acetylfuran.

Synthesis and fluorescence properties of Tb(Ⅲ) complexes with pyridine-2,6-dicarboxylic acid derivatives

Two novel ligands named 4-styrylpyridine-2,6-dicarboxylic acid (4-SPDA) and 4-(4-(2-(2, 6-dicarboxypyridin-4-yl)- vinyl)styryl)pyridine-2,6-dicarboxylic acid(DSPDA) and their complexes with Tb(Ⅲ) were synthesized and characterized by infrared spectrometry, 1H nuclear magnetic resonance, elemental analysis and gas chromatograph-mass spectrometry. The ligand synthetic route was optimized. The fluorescence properties of the complex in solid state, in different kind of solvents and in solutions with different pH values were investigated in detail. The results show that the yields of DSPDA and 4-SPDA reach over 78% by Wittig-Horner reaction and other eight pyridine-2, 6-dicarboxylic acid derivatives with different substituents on pyridine ring, and their complexes with Tb(Ⅲ) are also obtained. The fluorescence intensities of the complexes with electron-donating groups are more intense than those of the complexes with electron-withdrawing groups on pyridine ring; fluorescence intensities of the complexes are the strongest in neutral solution (pH=7), and the less the dipole moment of solvent molecule is, the stronger the fluorescence intensity is. It is found that the two ligands (4-APDA and DSPDA) are the good sensitizers for Tb(Ⅲ) ion.

The Synthesis of Pyridine 2,6-dicarboxylic Acid Using Microwave Irradiation

This research took 2,6-dimethylpyridine as raw materials under microwave irradiation to syntheses pyridine 2,6-dicarboxylic acid by adding oxidation potassium permanganate. However, there are lots of factors affecting the yield including the amount of potassium permanganate and sulfuric acid, reaction time, power, 2,6-dimethylpyridine dosage. We made the further research, using orthogonal experiment to find the optimal process conditions. Thus our research changed the synthesis process from a traditional method to a new type of microwave technology.

A Benzimidazole-pyridine-2,3-dicarboxylic Acid Bridged Zinc(Ⅱ)Coordination Complex–crystal Structure,Quantum Chemistry and Luminescence

The structure of a zinc（Ⅱ） coordination complex（1）, [C14 H10 N3 O5 Zn1.5]n or [Zn1.5（bzim）（pydc）（H2 O）]n（H2 pydc = pyridine-2,3-dicarboxylic acid, Hbzim = benzimidazole）, has been determined by X-ray crystallography and characterized by elemental analysis, IR spectrum and luminescence. Chemical formula： C14 H10 N3 O5 Zn1.5. It crystallizes in the monoclinic system, space group P21/c with a = 12.303（4）, b = 12.052（4）, c = 10.212（3） ？, β = 104.147（4）, V = 1468.3（8） ？3, Z = 4, Mr = 398.30, Dc = 1.802 g/cm3, F（000） = 800, μ = 2.501 mm-1 and S = 1.000. The 2-D network architecture of 1 is constructed from benzimidazole, zinc and pyridine-2,3-dicarboxylic acid. The quantum-chemical calculations have been performed on ‘molecular fragments’ extracted from the crystal structure using the B3 LYP method in Gaussian 09. The luminescence spectrum shows that complex 1 emits blue luminescence.

Hydrothermal Synthesis and Crystal Structure of a Coordinated Polymer: [Ni(pda)(H_2O)_3]_n (pda =Pyridine-2,3-dicarboxylate)

The coordinated polymer [Ni（pda）（H2O）3]n 1 （pda = pyridine-2,3-dicarboxylate） with one-dimensional chain structure has been obtained by hydrothermal method. Its structure was determined by X-ray crystallography with the following data： monoclinic, space group P21/c, a = 6.4153（4）, b = 21.6454（14）, c = 7.3783（5） A, β = 113.079（1）°, V = 942.56（11） A^3, Z = 4, C7H9NNiO7, Mr = 27.7.86, Dc = 1.958 g/cm^3,F（000） = 568 and μ（MoKa） = 2.081 mm^-1. The final R = 0.0194 and wR = 0.0515 for 1511 observed reflections with I 〉 2σ（I）. The title complex presents an infinite 1-D polymeric chain structure consisting of repeated basic units [Ni（pda）（H2O）3]n. The center Ni（Ⅱ） ions are coordinated by one nitrogen atom and three oxygen atoms from pda ligand as well as three H2O molecules in a slightly distorted octahedral environment. The intermolecular hydrogen bonds link the 1 D chains to form a 2D layered architecture.

Synthesis and Crystal Structure of a New One-dimensional Zn(II) Nitronyl Nitroxide Complex Bridged by Pyridine-2,4-dicarboxylate Anion

A new one-dimensional （1-D） Zn（Ⅱ） nitronyl nitroxide complex bridged by pyridine-2,4-dicarboxylate anion, [Zn（NIT4Py）（2,4-PDA）（H2O）2], （NIT4Py = 2-（4′-pyridyl）-4,4,5,5- tetramethylimidazoline-1-oxyl-3-oxide and 2,4-PDA = pyridine-2,4-dicarboxylate anion）, has been synthesized and structurally characterized by X-ray diffraction. It crystallizes in monoclinic, space group P21/c with a = 16.834（2）, b = 7.4376（10）, c = 18.295（3） A, β = 102.848（2）°, V = 2233.2（5） A^3, C19H23N4O3Zn, Mr = 500.78, Dc = 1.489 g/cm^3,μ（MoKa） = 1.152 mm^-1, F（000） = 1036, Z = 4, the final R = 0.0390 and wR = 0.0915 for 3234 observed reflections. In the complex, each zinc（Ⅱ） ion is six-coordinated by one nitrogen atom of the radical ligand （NIT4Py）, one nitrogen atom and two oxygen atoms of two 2,4-PDA anions and two oxygen atoms of two water molecules. Each 2,4-PDA anion bridges two Zn（Ⅱ） ions via a tridentate mode into a 1-D chain, and these 1-D chains are further linked into a 2-D network via hydrogen-bonding interactions.

Synthesis and Crystal Structure of [Zn(HPDB)_2(H_2O)_2]n·2nDMSO·2nH_2O (H_2-PDB = Pyridine-3,4-dicarboxylic Acid)

The title complex [Zn（HPDB）2（H2O）2]n·2nDMSO·2nH2O（H2-PDB is pyridine-3, 4-dicarboxylic acid and DMSO the dimethyl sulphoxide） was synthesized under traditional solution condition. Its crystal （C18H28N2O14S2Zn） belongs to monoclinic system, space group P21/c with a = 8.2791 （6）, b = 12.5495（10）, c = 13.6519（ 11 ）A°, β = 105.294（2）°, V = 1368.18（18）A°^3, Z = 2, Mr = 625.91, Dx = 1.514 g/cm^3,μ = 1.117 mm^-1, F（000） = 648, R = 0.0654 and wR = 0.1654 for 2414 observed reflections （I 〉 2σ（I））. It has a 2-D planar network, in which the Zn atom is six-coordinated and hydrogen bonds between carboxylate groups, DMSO and water molecules result in the final 3D structure.

The mechanism of unexpected reduction of dimethyl pyridine-2,3-dicarboxylate to l,2,3,4-tetrahydrofuro[3,4-b]-pyridin-5(7H)-one with sodium borohydride

An unexpected reduction of dimethyl pyridine-2,3-dicarboxylate to 1,2,3,4-tetrahydrofuro[3,4-b]pyridin-5（7H）-one with sodium borohydride in ethanol and tetrahydrofuran, respectively, is described, a hypothetic mechanism for the unusual reductive product is proposed.

Rapid Microwave-accelerated Multi-step Synthesis of 2,6-di（naphthalene Thioureido Carbamino）Pyridine

A rapid and simple procedure for synthesis of 2,6-di（naphthalene thioureido carbamino）pyridine fluorescine anion acceptor by the reaction between pyridine-2,6-dicarbohydrazide obtained from 2,6-dimethylpyridine after three-step reaction and 1-napbthyl isothiocyanate is described, and all reactions could be carried out under microwave heating condition.

Synthesis, Structure and Property of a Novel Coordination Polymer [Tb(C_7H_3NO_4)(C_6H_4NO_2)(H_2O)]

A novel terbium(III) coordination polymer [Tb(C7H3NO4)(C6H4NO2)(H2O)] was successfully synthesized hydrothermally and characterized by single-crystal X-ray diffraction. The complex is of monoclinic, space group P21/c with a = 9.2252(11), b = 14.1477(16), c = 10.5134(12) A, β = 95.770(2)°, V = 1365.2(3) A3, Z = 4, Dc = 2.248 g·cm-3, F(000) = 880, the final R = 0.0176 and w R = 0.0411 for 2149 observed reflections with I 】 2σ(I). The complex is extended into a three-dimensional network structure with 24-atom rings which are composed of Tb, C and O atoms. The complex displays green fluorescence emission in the solid state at room temperature, which corresponds to 5D4 → 7F5 transition of the Tb(III) ion.

A Chain Structure Based on Homodinuclear Scandium Units: [Sc(μ-OH)(2,5-pydc)(H_2O)]_n

The reaction of pyridine-2,5-dicarboxylic acid with Sc2O3 under hydrothermal con- dition yields a new complex [Sc（μ-OH）（2,5-pydc）（H2O）]n 1 which has a chain structure based on homodinuclear scandium units. Crystal data for 1： space group P^-1, a = 6.7192（13）, b = 7.6131（13）, c = 8.9313（14） A, α = 95.976（6）, β = 101.663（6）, γ = 108.151（5）^o, V= 418.26（13） A^3, Z = 2, Dc = 1.946 g/cm^3, g = 0.889 mm^-1, F（000） = 248, C7H6NO6Sc, Mr = 245.09, the final R = 0.0429 and wR = 0.1086.

Syntheses and Crystal Structures of Four New Complexes [Mn(4,4′-bip)_2(OH_2)_4](DBA)·4H_2O and [M(OH_2)(HDPA)_2]·3H_2O (M = Mn,Co,Ni)

Four new transition metal complexes, [Mn（4,4′-bip）2（OH2）4]（DBA）-4H2O 1 （4,4′-hip = 4,4′-bipyridine, H2DBA = benzene-1,3-dicarboxylic acid） and [M（OH2）（HDPA）2]-3H2O （M = Mn 2, M = Co 3, M = Ni 4, H2DPA = 2,6-pyridine-dicarboxylic acid）, have been prepared from the reaction of transition metals and carboxylic acids, and characterized by X-ray and elemental analyses. For compound 1, the packing diagram shows that a three-dimensional network is formed via hydrogen bonds and strong π-πinteractions. For compounds 2, 3 and 4, a double-helical chain is formed through hydrogen bonds. Moreover, a three-dimensional network is constructed from chains via complicated hydrogen bonds between crystal water molecules and oxygen atoms of HDPA^-.

PdCl_2-catalyzed heterocyclotrimerization in MeOH/scCO_2:A versatile approach to dimethyl pyridine-3,5-dicarboxylate from methyl acrylate and urea

A novel and green method for the synthesis of dimethyl pyridine-3,5-dicarboxylate has been developed. It is PdCl2-catalyzed heterocyclotrimerization of methyl acrylate with urea in methanol/supercritical carbon dioxide. The target compound was obtained with a 75% isolated yield under the optimized con-ditions.

One-pot Synthesis of 1,5-Diaza-2,6-cyclooctadiene-3,7-dicarboxylates Through a Multiple-component Reaction

Methyl propiolate, formaldehyde, and various acyclic amines were assembled in one-pot into a series of 1,5-diaza-2,6-cyclooctadiene-3,7-dicarboxylates in moderate to good yields. This multiple-component reaction benefits from operational simplicity as well as good material economy.

Synthesis, Structure and Luminescent Properties of Three 1D Chain Rare Earth Complexes

Three 1 D chain coordination polymers [Ln(pydc)2(H2 O)2]n·n Him(Ln = Dy(1), Gd(2), Sm(3), H2 pydc = pyridine-2,5-dicarboxylic acid, Im = imidazole), were solvothermally synthesized by the reaction of pyridine-2,5-dicarboxylic acid(H2 pydc), Ln(Ⅲ) salts and imidazole. They have been characterized by X-ray single-crystal diffraction, IR spectra, TGA analysis and elemental analysis. Structural analyses revealed that complexes 1~3 have similar 1 D chain structures and belong to P1 space group. It is noteworthy that complexes 1~3 exhibited excellent thermal stability and no weightlessness below 117 ℃. Meanwhile, 1 and 3 show characteristic fluorescence of corresponding lanthanide metal ions in solid state at room temperature.

Synthesis, Crystal Structure and Luminescence of a New Europium(Ⅲ) Coordination Polymer with Imidazole Carboxylic Ligand

A new luminescent compound, {[Eu3（L）4（H2 O）8]·（NO3）·4 H2 O}n（1, H2 L = 2-（pyridine-3-yl）-imidazole-4,5-dicarboxylic acid） has been solvothermally synthesized and structurally characterized by elemental analyses, IR and single-crystal X-ray diffraction. 1 crystallizes in monoclinic, space group C2/c with a = 21.0183（19）, b = 9.5227（6）, c = 28.227（3） ?, β = 106.885（5）o, V = 5406.1（8） ?3, Dc = 2.038 g/cm3, μ = 3.358 mm-1, Mr = 1658.76, F（000） = 3247, Z = 4, the final R = 0.0488, wR = 0.1195 and S = 1.075. The deprotonated L ligand employs a μ4-bridge to coordinate with three Eu（Ⅲ） ion, forming a wave-like（3,4）-connected 2 D structure. The existence of π···π interaction between the pyridine rings of L ligands leads to an infinite 3 D network. Furthermore, the thermal analysis, powder diffraction and solid-state photoluminescent properties of compound 1 have also been investigated.

Synthesis and luminescent properties of novel pyrazolone rare earth complexes

A novel pyrazolone pyridine-containing ligand, 2,6-bis（1-phenyl-4-ethoxycarbonyl-5-pyrazolone-3-yl）pyridine （H2L） was designed and synthesized from pyridine-2,6-dicarboxylic acid （1）, and its Eu（III） and Tb（III） complexes were prepared. The ligand and complexes were characterized in detail based on FT-IR spectra, ^1H NMR, elemental analysis and thermal analysis, and the formula of Ln2L3·4H2O （Ln=Eu or Tb） of rare earth complexes was confirmed. The UV-vis absorption spectra and photoluminescence properties of the complexes were investigated, which showed that the Eu（III） and Tb（III） ions could be sensitized efficiently by the ligand （H2L） and emit the photolumi- nescence with high intensity, narrow half-peak width, and monochromic light. The results indicated that the complexes showed potential as excellent luminescent materials.

A 4d-4f heterometallic coordination polymer: Synthesis, crystal structure and near-infrared luminescent properties

A 4d-4f heterometallic coordination polymer, [AgNd（pydc）2].2H2O （1） （H2pydc=pyridine-3,4-dicarboxylic acid）, was synthesized under hydrothermal conditions, and fimher characterized by elemental analysis, IR, thermogravimetric analysis and single-crystal X-ray dif- fraction. Complex 1 featured a three-dimensional （3D） framework containing one-dimensional （1D） channels occupied by free water molecules, which was constructed from 1D inorganic heterometallic chains and linear pydc linkers. To our knowledge, complex 1 represented a rare example of 3D open-framework 4d-4f heterometallic coordination polymer. After removal of the water molecules fi＇om complex 1, the remaining material had high thermal stability. Moreover, the near-infrared luminescent properties of 1 were also investigated in the solid state.