- A “Thermodynamically Stable” 2D Nickel Metal–Organic Framework over a Wide pH Range with Scalable Preparation for Efficient C2s over C1 Hydrocarbon Separations
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The design and construction of “thermodynamically stable” metal–organic frameworks (MOFs) that can survive in liquid water, boiling water, and acidic/basic solutions over a wide pH range is highly desirable for many practical applications, especially adsorption-based gas separations with obvious scalable preparations. Herein, a new thermodynamically stable Ni MOF, {[Ni(L)(1,4-NDC)(H2O)2]}n (IITKGP-20; L=4,4′-azobispyridine; 1,4-NDC=1,4-naphthalene dicarboxylic acid; IITKGP stands for the Indian Institute of Technology Kharagpur), has been designed that displays moderate porosity with a BET surface area of 218 m2 g?1 and micropores along the [10?1] direction. As an alternative to a cost-intensive, cryogenic, high-pressure distillation process for the separation of hydrocarbons, MOFs have recently shown promise for such separations. Thus, towards an application standpoint, this MOF exhibits a higher uptake of C2 hydrocarbons over that of C1 hydrocarbon under ambient conditions, with one of the highest selectivities based on the ideal adsorbed solution theory (IAST) method. A combination of two strategies (the presence of stronger metal–N coordination of the spacer and the hydrophobicity of the aromatic moiety of the organic ligand) possibly makes the framework highly robust, even stable in boiling water and over a wide range of pH 2–10, and represents the first example of a thermodynamically stable MOF displaying a 2D structural network. Moreover, this material is easily scalable by heating the reaction mixture at reflux overnight. Because such separations are performed in the presence of water vapor and acidic gases, there is a great need to explore thermodynamically stable MOFs that retain not only structural integrity, but also the porosity of the frameworks.
- Sahoo, Rupam,Chand, Santanu,Mondal, Manas,Pal, Arun,Pal, Shyam Chand,Rana, Malay Kumar,Das, Madhab C.
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- Control over catenation in metal-organic frameworks via rational design of the organic building block
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(Chemical Equation Presented) Metal-organic frameworks (MOFs), a hybrid class of materials comprising inorganic nodes and organic struts, have potential application in many areas due to their high surface areas and uniform pores and channels. One of the key challenges to be overcome in MOF synthesis is the strong propensity for catenation (growth of multiple independent networks within a given crystal), as catenation reduces cavity sizes and diminishes porosity. Here we demonstrate that rational design of organic building blocks, which act as strut-impervious scaffolds, can be exploited to generate highly desired noncatenated materials in a controlled fashion.
- Farha, Omar K.,Malliakas, Christos D.,Kanatzidis, Mercouri G.,Hupp, Joseph T.
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- Synthesis and characterization of four novel manganese(II) chains formed by 4,4′-azobis(pyridine) and benzoate or nitrobenzoates: Stabilization of unusual ladder structures
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Four new manganese(II) coordination polymers: [Mn(4,4′-azpy)(C 6H5COO)2](4,4′-azpy)0.5 (1), [Mn(4,4′-azpy)(p-(NO2)C6H4COO) 2] (2), [Mn(4,4′-azpy)(m-(NO2)C6H 4COO)2] (3) and [Mn(4,4′-azpy)(o-(NO 2)C6H4COO)2(H2O) 2] (4), where 4,4′-azpy = 4,4′-azobis(pyridine), have been synthesized by self-assembly of MnX2 (X = benzoate, p-, m-, or o-nitrobenzoates) together with 4,4′-azpy. All four complexes were characterized by elemental analyses, IR spectroscopy, thermal analyses, single-crystal X-ray diffraction analyses and variable-temperature magnetic measurements. The structural analyses reveal that complexes 1, 2 and 3 feature a 1D molecular ladder formed by syn-syn (complex 1) or syn-anti (complexes 2 and 3) carboxylate-bridged dimeric Mn(II) units which are joined together by 4,4′-azpy ligands. In complex 1, these ladders assemble with the help of π-π and C-H?π interactions to form a nanoporous framework that incorporates non coordinated 4,4′-azpy molecules by exploiting host-guest C-H?π and hydrogen bonding interactions. Complex 2 presents a 3D supramolecular framework by π-π and CH?π interactions, whereas, complex 3 having a similar ladder structure to 1 and 2, forms a 2D grid through π-π interactions. On the other hand, complex 4 is a 4,4′-azpy bridged fish-bone chain of carboxylate-coordinated mononuclear manganese(II) units, which are linked together by strong hydrogen bonds to form a 2D structure. Variable-temperature (2-300 K) magnetic susceptibility measurements show the presence of weak antiferromagnetic interactions within the discrete Mn-(OCO)2-Mn dimers for complexes 1, 2 and 3 that have been fitted with a S = 5/2 dimer model (J = -0.8, -0.5 and -0.4 cm-1 respectively). The magnetic data of complex 4 can be reproduced with a S = 5/2 monomer model including a Zero Field Splitting (|D| = 1.7 cm-1).
- Kar, Paramita,Drew, Michael G.B.,Gómez-García, Carlos J.,Ghosh, Ashutosh
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- Two Closely Related Zn(II)-MOFs for Their Large Difference in CO2 Uptake Capacities and Selective CO2 Sorption
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Two azo functionalized Zn(II)-based MOFs, {[Zn(SDB)(3,3′-L)0.5]·xG}n, IITKGP-13A, and {[Zn2(SDB)2(4,4′-L)]·xG}n, IITKGP-13B (IITKGP stands for Indian Institute of Technology Kharagpur), have been constructed through the self-assembly of isomeric N,N′-donor spacers (3,3′-L = 3,3′-azobispyridine and 4,4′-L = 4,4′-azobispyridine) with organic ligand 4,4′-sulfonyldibenzoic acid (SDBH2) and Zn(NO3)2·6H2O (G represents disordered solvent molecules). Single-crystal X-ray diffraction studies reveal the 2D structure with sql topology for both MOFs. However, the subtle change in positions of coordinating N atoms of spacers makes IITKGP-13A noninterpenetrated, while IITKGP-13B bears a 2-fold interpenetrated structure. IITKGP-13A exhibits higher uptake of CO2 over CH4 and N2 with high IAST selectivities for mixed CO2/CH4 (50:50, biogas) and CO2/N2 (15:85, flue gas) gas systems. In contrast, IITKGP-13B takes up very low amount of CO2 gas (0.4 mmol g-1) compared to IITKGP-13A (1.65 mmol g-1) at 295 K. Density functional theory (DFT)-based electronic structure calculations have been performed to explain the origin of the large differences in CO2 uptake capacity between the two MOFs at the atomistic level. The results show that the value of the change in enthalpy (ΔH) at 298 K temperature and 1 bar pressure for the CO2 adsorption is more negative in IITKGP-13A as compared to that in IITKGP-13B, thus indicating that CO2 molecules are more favored to get adsorbed in IITKGP-13A than in IITKGP-13B. The computed values for the Gibbs' free energy change (ΔG) for the CO2 adsorption are positive for both of the MOFs, but a higher value is observed for the IITKGP-13B. The noncovalent types of interactions are the main contribution toward the attractive energies between the host MOF frameworks and guest CO2 molecules, which has been studied with the help of energy decomposition analysis (EDA).
- Chand, Santanu,Chattaraj, Pratim K.,Das, Madhab C.,Das, Prasenjit,Pal, Arun,Saha, Ranajit,Sahoo, Rupam
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- 4-Pyridylnitrene and 2-pyrazinylcarbene
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Both flash vacuum thermolysis (FVT) and matrix photolysis generate 2-diazomethylpyrazine (22) from 1,2,3-triazolo[1,5- a]pyrazine (24). FVT of 4-azidopyridine (18) as well as of 24 or 2-(5-tetrazolyl)pyrazine (23) affords the products expected from the nitrene, i.e., 4,4'-azopyridine and 2- and 3-cyanopyrroles. Matrix photolyses of both 18 and 24 result in ring expansion of 4-pyridylnitrene/2-pyrazinylcarbene to 1,5-diazacyclohepta-1,2,4,6-tetraene (20). Further photolysis causes ring opening to the ketenimine 27.
- Wentrup, Curt,Reisinger, Ales,Kvaskoff, David
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- Bifunctional Cs?Au/Co3O4 (Basic and Redox)-Catalyzed Oxidative Synthesis of Aromatic Azo Compounds from Anilines
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An eco-friendly alkali-promoted (Cs?Au/Co3O4) catalyst, with redox and basic properties for the oxidative dehydrogenative coupling of anilines to symmetrical and unsymmetrical aromatic azo compounds, was developed. We realized a base additive- and molecular O2 oxidant-free process (using air), with reasonable reusability of the catalyst achieved under milder reaction conditions. Notably, the enhanced catalytic activity was also linked to the increased basic site concentration, low reduction temperatures, and the effect of lattice oxygen on the nanomaterials. The increased basic strength of the cation-promoted catalyst improved the electron density of the active Au species, resulting in higher yields of the desired aromatic azo compounds.
- Oseghale, Charles O.,Fapojuwo, Dele Peter,Alimi, Oyekunle Azeez,Akinnawo, Christianah Aarinola,Mogudi, Batsile M.,Onisuru, Oluwatayo Racheal,Meijboom, Reinout
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supporting information
p. 5063 - 5073
(2021/09/30)
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- Electrochemical dehydrogenation of hydrazines to azo compounds
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A strategy for the electrochemical dehydrogenation of hydrazine compounds is disclosed under ambient conditions. This protocol proceeded smoothly in ethanol by employing electrons as clean oxidants. Its synthetic value is well demonstrated by the highly efficient synthesis of symmetric and unsymmetric azo compounds. It is an environmentally friendly transformation and the present protocol was effective on a large scale.
- Du, Ke-Si,Huang, Jing-Mei
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supporting information
p. 1680 - 1685
(2019/04/08)
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- Reversing Chemoselectivity: Simultaneous Positive and Negative Catalysis by Chemically Equivalent Rims of a Cucurbit[7]uril Host
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Enzyme catalysis has always been an inspiration and an unattainable goal for chemists due to features such as high specificity, selectivity, and efficiency. Here, we disclose a feature neither common in enzymes nor ever described for enzyme mimics, but one that could prove crucial for the catalytic performance of the latter, namely the ability to catalyze and inhibit two different reactions at the same time. Remarkably, this can be realized by two identical, spatially resolved catalytic sites. In the future, such a synchronized catalyst action could be used not only for controlling chemoselectivity, as in the present case, but also for regulating other types of chemical reactivity.
- Rad, Nazar,Danylyuk, Oksana,Sashuk, Volodymyr
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supporting information
p. 11340 - 11343
(2019/07/16)
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- Induction of chirality in 4,4′-azopyridine by halogen-bonding interaction with optically active ditopic donors
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Optically active ditopic halogen bond donors bearing two 4-iodotetrafluorophenyl groups were obtained by reaction of chiral diols with iodopentafluorobenzene. Co-crystallization of these donors with anti-4,4′-azopyridine afforded binary complexes containing infinite chains of the alternating component molecules connected by halogen bonds. The solid state CD measurements confirmed that complexation induces optical activity of the azo chromophore due to the twisting of the aryl-N═N system or external chiral perturbation exerted by host molecules.
- Alfuth, Jan,Chojnacki, Jaros?aw,Po?oński, Tadeusz,Olszewska, Teresa
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p. 5512 - 5517
(2019/04/04)
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- Thermally Twistable, Photobendable, Elastically Deformable, and Self-Healable Soft Crystals
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The first example of a smart crystalline material, the 2:1 cocrystal of probenecid and 4,4′-azopyridine, which responds reversibly to multiple external stimuli (heat, UV light, and mechanical pressure) by twisting, bending, and elastic deformation without fracture is reported. This material is also able to self-heal on heating and cooling, thereby overcoming the main setbacks of molecular crystals for future applications as crystal actuators. The photo- and thermomechanical effects and self-healing capabilities of the material are rooted in reversible trans–cis isomerization of the azopyridine unit and crystal-to-crystal phase transition. Fairly isotropic intermolecular interactions and interlocked crisscrossed molecular packing secure high elasticity of the crystals.
- Gupta, Poonam,Karothu, Durga Prasad,Ahmed, Ejaz,Naumov, Pan?e,Nath, Naba K.
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supporting information
p. 8498 - 8502
(2018/07/14)
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- Dehydrogenation of the NH?NH Bond Triggered by Potassium tert-Butoxide in Liquid Ammonia
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A novel strategy for the dehydrogenation of the NH?NH bond is disclosed using potassium tert-butoxide (tBuOK) in liquid ammonia (NH3) under air at room temperature. Its synthetic value is well demonstrated by the highly efficient synthesis of aromatic azo compounds (up to 100 % yield, 3 min), heterocyclic azo compounds, and dehydrazination of phenylhydrazine. The broad application of this strategy and its benefit to chemical biology is proved by a novel, convenient, one-pot synthesis of aliphatic diazirines, which are important photoreactive agents for photoaffinity labeling.
- Wang, Lei,Ishida, Akiko,Hashidoko, Yasuyuki,Hashimoto, Makoto
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supporting information
p. 870 - 873
(2017/01/14)
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- Characterization and magnetic properties of two novel copper(II) coordination polymers prepared by different synthetic techniques
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Two novel ternary Cu(II) coordination polymers with formulas {[Cu(μ2-AZPY)(H2BTC)2]}n (1) and {[Cu(μ2-AZPY)(μ2-HBTC)(H2O)]·AZPY}n (2) (AZPY – trans-4,4′-azobis(pyridine), BTC – benzene-1,3,5-tricarboxylate) have been synthesized using the solvothermal or diffusion techniques, respectively. Compounds were characterized by single crystal X-ray diffraction, thermogravimetry, infrared spectroscopy, elemental analysis and AAS. Removal of water and AZPY from the framework of 2 was investigated by wide-angle X-ray scattering measurements during in-situ heating. A magnetic study showed on antiferromagnetic coupling in 1 and 2 and magnetic properties may be influenced by both crystal field (CF) and inter-molecular interactions. The effective magnetic moment decreases from the values μeff = 4.97 μB for 1 and μeff = 3.39 μB for 2 at T = 290 K to the values of μeff = 1.41 μB for 1 and μeff = 1.27 μB for 2 at T = 2 K. The origin of the observed behavior is discussed.
- Almá?i, Miroslav,Zeleňák, Vladimír,Zeleňáková, Adriana,Vargová, Zuzana,Císa?ová, Ivana
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- 4,4'-Azopyridine as an easily prepared and recyclable oxidant for synthesis of symmetrical disulfides from thiols or alkyl halides(tosylates)/thiourea
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Heterocyclic azo compounds, prepared from corresponding amines in one step, are used as effective oxidants for the conversion of thiols into symmetrical disulfides in high yields. Among the studied azo compounds, 4,4'-azopyridine was found to be very efficient for the odorless conversion of alkyl halides into disulfides in the presence of thiourea. An attractive feature of this azo compound is that its obtained solid side product hydrazine is easily separated by filtration and can be recycled to its azo compound for further use.
- Khalili, Dariush,Iranpoor, Nasser,Firouzabadi, Habib
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p. 544 - 555
(2015/10/19)
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- Interdependence of structure and physical properties in co-crystals of azopyridines
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To establish how intermolecular interactions influence the supramolecular assembly of azopyridines, a total of five co-crystals of 3,3′ and 4,4′-azopyridine; 3,3′-azpy:succinic acid (3,3′-azpy:SA), 3,3′-azpy:adipic acid (3,3′-azpy:AA), 3,3′-azpy:suberic acid (3,3′-azpy:SuA), 3,3′-azpy:sebacic acid (3.3′-azpy:SeA), and 4,4′-azpy:suberic acid (4,4′-azpy:SuA) were synthesized. In all co-crystals of 3,3′-azopyridine, there are infinite 1-D zig-zag tapes composed of alternating 3,3′-azpy and diacids held together by COOH...N(py) hydrogen bonds. Neighbouring chains are arranged into 2-D sheets via secondary inter-chain C-H...O interactions between azopyridine ring hydrogen atoms and carbonyl oxygen atoms in an in-phase manner. However, in the co-crystal of 4,4′-azopyridine:suberic acid, the adjacent chains form 2-D sheets in an out-of-phase motif via two types of inter-chain C-H...O interactions, i.e. between azopyridine ring hydrogen atoms and carbonyl oxygen as well as hydroxyl oxygen atoms. The structural consistency within the 3,3′-azopyridine co-crystals has made it possible to establish a correlation between melting point of the homomeric molecular solids and co-crystals of the corresponding carboxylic acids.
- Aakeroey, Christer B.,Panikkattu, Sheelu,Dehaven, Baillie,Desper, John
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p. 463 - 470
(2013/03/13)
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- Pillaring role of 4,4′-azobis(pyridine) in substituted malonate-containing manganese(II) complexes: Syntheses, crystal structures, and magnetic properties
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Six new manganese(II) complexes of formulas [Mn2(Rmal) 2(H2O)2(azpy)]n (1-3), [Mn(Phmal)(H2O)(azpy)]n (4), [Mn2(Et 2mal)2(H2O)4(azpy)2] n (5), and [Mn(Bzmal)(H2O)3(azpy)] (6) [azpy = 4,4′-azobispyridine (1-6), Rmal = methylmalonate (Memal) (1), dimethylmalonate (Me2mal) (2), and butylmalonate (Butmal) (3), Phmal = phenylmalonate (4), Et2mal = diethylmalonate (5), and Bzmal = benzylmalonate (6)] were synthesized and structurally characterized by single-crystal X-ray diffraction. Complexes 1-3 are three-dimensional compounds whose structure consists of corrugated layers of manganese(II) linked through syn-anti carboxylate (Rmal) bridges, which are pillared through the bis-monodentate azpy molecule. Complex 4 has a layered structure of manganese(II) ions connected by carboxylate (Phmal) bridges in the syn-anti coordination mode as in 1-3, the azpy group acting here as a terminally bound monodentate ligand. The structure of 5 consists of Et2mal-Mn(II) neutral chains linked through the azpy ligand, giving rise to a complex three-dimensional network. Complex 6 is constituted by neutral [Mn(Bzmal)(H 2O)3(azpy)] mononuclear units, which are interlinked through O-H???O, O-H???N, and π-π type intermolecular interactions to afford a three-dimensional supramolecular structure. The topological analysis of these crystallographic structures shows the occurrence of four different nets: a (3,4)-connected InS-type (1-3), a binodal layered hcb (4), a uninodal CdS-type (5), and a (4,5)-connected tcs topology (6). The magnetic properties of 1-5 were investigated in the 2.0-300 K temperature range. Overall antiferromagnetic behavior occurs in 1-4 with susceptibility maxima in the range 2.8-5.5 K, the exchange pathway being provided by the syn-anti carboxylate (substituted malonate) bridge [manganese-manganese separation in the range 5.4365(3)-5.5274(1) A]. Very weak antiferromagnetic interactions are observed in 5 through the trans-bis-monodentate Et2mal ligand, the intrachain manganese-manganese separation being 7.328(3) A. The much larger manganese-manganese separation through the bis-monodentate azpy ligand in 1-5 (values greater than 13.5 A) accounts for the lack of any significant magnetic interaction though this extended bridge.
- Deniz, Mariadel,Hernandez-Rodriguez, Irene,Pasan, Jorge,Fabelo, Oscar,Canadillas-Delgado, Laura,Ruiz-Perez, Catalina,Yuste, Consuelo,Julve, Miguel,Lloret, Francesc
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p. 4505 - 4518,14
(2020/08/31)
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- 4,4'-azobis(halopyridinium) derivatives: Strong multidentate halogen-bond donors with a redox-active core
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In summary, an easily accessible class of highly potent bis(pyridinium)-based multidentate XB donors has been introduced, which, in addition to their inherent XB acidity, also include a built-in redox option. In the previously established benchmark reaction to test the carbon-bromine bond-activation potential of XB donors, these compounds (2a, 2a', and 2b) are slightly more effective than bis(imidazolium)- based XB donors. Initially, the analysis of the overall process was complicated by the oxidation of bromide to elemental bromine by the azobis(halopyridinium) compounds during the reaction. The bromine thus formed was part of an additional activation process, which could, however, be suppressed by addition of cyclohexene. Two directions will be pursued in future work: since we demonstrated the activation capabilities of pyridinium-based XB donors towards carbon-bromine bonds, we plan to develop other types of activating reagents with redox-innocent bridging motives. Parallel to this, we strive to exploit the coupled oxidation/ XB-activation potential of the activators presented herein in suitable reactions.
- Kniep, Florian,Walter, Sebastian M.,Herdtweck, Eberhardt,Huber, Stefan M.
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supporting information; experimental part
p. 1306 - 1310
(2012/03/26)
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- The first mitsunobu protocol for efficient synthesis of α-acyloxyphosphonates using 4,4′-azopyridine
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This is the first report on applying the Mitsunobu protocol for the synthesis of various α-acyloxyphosphonates using 4,4′-azopyridine and PPh3 with diverse aromatic and aliphatic carboxylic acids. Under these conditions, diethyl azodicarboxylat
- Iranpoor, Nasser,Firouzabadi, Habib,Khalili, Dariush
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experimental part
p. 2166 - 2171
(2012/04/04)
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- New heteroaromatic azo compounds based on pyridine, isoxazole, and benzothiazole for efficient and highly selective amidation and mono-N-benzylation of amines under Mitsunobu conditions
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4,4′-Azopyridine (2c) is used in conjunction with triphenylphosphine for the efficient conversion of carboxylic acids into amides via Mitsunobu reaction with primary and secondary aliphatic and aromatic amines. The highly selective amidation of only primary aromatic amines with new heterogeneous azo compounds based on benzothiazole 2d and isoxazole 2e is also described. These azo compounds 2c-2e can also be applied for selective mono-N-benzylation of primary aromatic amines. The solid side product heteroaromatic hydrazines obtained under the developed Mitsunobu conditions are easily separated by simple filtration and can be reoxidized to azo compounds for further use.
- Iranpoor, Nasser,Firouzabadi, Habib,Khalili, Dariush
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experimental part
p. 923 - 934
(2010/10/01)
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- Easily prepared azopyridines as potent and recyclable reagents for facile esterification reactions. An efficient modified mitsunobu reaction
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(Chemical Equation Presented) The 2,2′-, 3,3′-, and 4,4′-azopyridines (azpy) and their alkyl pyridinium ionic liquids were studied as a new class of electron-deficient reagents for Mitsunobu esterification reactions. Among these compounds, 4,4′-azopyridine was found to be the most suitable one for esterification and thioesterification reactions. This new reagent promises to provide general and complementary solutions for separation problems in Mitsunobu reactions without restricting the reaction scope and facilitates the isolation of its hydrazine byproduct. The pyridine hydrazine byproduct can be simply recycled to its azopyridine by an oxidation reaction.
- Iranpoor, Nasser,Firouzabadi, Habib,Khalili, Dariush,Motevalli, Somayeh
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p. 4882 - 4887
(2008/09/21)
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- Iron(II) molecular framework materials with 4,4′-azopyridine
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Three new iron(II) molecular-framework materials incorporating the bridging ligand 4,4′-azopyridine (azpy) have been synthesized and structurally characterized: Fe2(azpy)4(NCS)4 ·(azpy) (A), Fe(azpy)(NCSe)2(EtOH)2 · (azpy) (B), and Fe(azpy)2(NCSe)2 · 2(MeCN) (C). A and C consist of non-interpenetrating (4,4) grids of iron(II) centres bridged by azpy ligands with non-coordinating azpy ligands or acetonitrile molecules occupying the spaces within and between the layers. For B, hydrogen-bonding interactions between coordinated ethanol molecules and non-coordinated azpy ligands link linear Fe-azpy chains to give a two-dimensional framework. CSIRO 2005.
- Halder, Gregory J.,Kepert, Cameron J.
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p. 311 - 314
(2007/10/03)
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- Mass spectrometric characterization and gas-phase chemistry of self-assembling supramolecular squares and triangles
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A detailed mass spectrometric characterization of self-assembling polynuclear metal complexes is described. The complexes can only be ionized as intact species under a surprisingly narrow range of conditions by electrospray ionization. Comparison with the results from NMR experiments shows that several solution-phase features of these squares and triangles (such as trends in bond energies, ligand-exchange reactions, or square-triangle equilibria) are qualitatively reflected in the gas-phase data. Consequently, mass spectrometry represents a valuable method for the characterization of these compounds. Nevertheless, the formation of unspecific aggregates during the ionization process occurs and its implications are discussed. Beyond the chemistry in solution, the fragmentation pathways of these complexes in the gas phase have been studied by infrared multiphoton dissociation (IRMPD) experiments. The results of IRMPD studies allow us to draw conclusions with respect to the structure and energetics of fragmentation products. In this tandem MS experiment, reaction pathways can be observed directly which can hardly be analyzed in solution. According to these results, the equilibration of triangles and squares involves the supramolecular analogue of a neighboring-group effect.
- Schalley, Christoph A.,Mueller, Thomas,Linnartz, Petra,Witt, Matthias,Schaefer, Mathias,Luetzen, Arne
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p. 3538 - 3551
(2007/10/03)
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- Azopyridinium-containing [2]pseudorotaxanes and hydrazopyridinium-containing [2]catenanes
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Benzylation of 4,4′-azopyridine, followed by counterion exchange, yields the bis(hexafluorophosphate) salt of the dibenzyl-4,4′-azopyridinium dication, which is bound by bis-p-phenylene-34-crown-10 (BPP34C10) and by 1,5-dioxynaphtho-38-crown-10 (1/5DN38C1
- Ashton, Peter R.,Brown, Christopher L.,Cao, Jianguo,Lee, Ju-Young,Newton, Simon P.,Raymo, Francisco M.,Stoddart, J. Fraser,White, Andrew J. P.,Williams, David J.
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p. 957 - 965
(2007/10/03)
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- A novel synthesis of unsymmetrical azo aromatics inaccessible by diazo-coupling reaction
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A novel synthesis of unsymmetrical azo aromatics inaccessible by diazo-coupling reaction is reported. The synthesis involved the reaction of acetanilides with nitroarenes under moderate reaction conditions. A reaction pathway via a nitrosoarene intermediate involving elimination of the elements of the acetate anion, is proposed.
- Ayyangar,Naik,Srinivasan
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p. 7253 - 7256
(2007/10/02)
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- Photoreponsive Crown Ethers. Part 7. Proton and Metal Ion Catalyses in the cis-trans Isomerisation of Azopyridines and an Azopyridine-bridged Cryptand
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A 2,2'-azopyridine-bridged crown ether (5) has been synthesised for the purpose of controlling the ion-binding functions by an on-off light switch mechanism.Since the trans-azopyridine moiety of compound (5) is vertically over the crown ether ring and the photoisomerised cis-azopyridine moiety of (5) is almost parallel to the crown ether plane, it would be expected that only the pyridine nitrogen of trans-(5) are capable of co-ordinating to metal ions bound into the crown ether ring.The thermal isomerisation of cis-2,2'-azopyridine to trans-2,2'-azopyridine was speeded up either by protonation of the pyridine nitrogen or by complexation with heawy-metal ions (e.g.Cu2+, Ni2+, and Co2+).Similarly, the thermal isomerisation of cis-(5) to trans-(5) was speeded up by protonation of azopyridine, but the metal ion catalysis was observed only for the metal ions which were bound into the crown ether ring (e.g.Cu2+ and Pb2+).The result of solvent extraction of alkali-metal ions with (5) was very similar to that with an azobenzene-bridged crown ether (1), indicating that the 2,2'-azopyridine-bridge of (5) has almost no effect on the extraction of alkali-metal ions.On the other hand, trans-(5) was capable of extracting considerable amounts of heavy-metal ions (Cu2+, Ni2+, CXo2+, and Hg2+), whereas photoisomerised cis-(5) scarcely extracted these metal ions.Such a difference in the extractability was not observed between trans-(1) and photoisomerised cis-(1).Neither the trans- nor the cis-form of 6,6'-bis(morpholinocarbonyl)-2,2'-azopyridine could extract these metal ions under comparable extraction conditions.These results suggest that pyridine nitrogens of trans-(5) are directed towards the crown ether plane so as to co-ordinate to metal ions in the crown ether ring, whereas those of cis-(5) have no such coordination ability due to the distorted configuration.Therefore, compound (5) would act as a 'photoresponse cryptand' for heavy metal ions.
- Shinkay, Seiji,Kouno, Takeshi,Kusano, Yumiko,Manabe, Osamu
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p. 2741 - 2748
(2007/10/02)
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- Seed treatment fungicides for control of seed-borne diseases
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This invention relates to a method for controlling seedborne fungus diseases in plants, by applying to the seed a fungicidally effective amount of 4,4'-azodipyridine or acid salts of the formula STR1 wherein A is an acid having acidic dissociation constant greater than 1×10-6 ; and P is equal to the number of hydrogens on the acid A which have an acidic dissociation constant greater than 1×10-6.
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