- Multiplying the electron storage capacity of a bis-tetrazine pincer ligand
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An unexpected doubling in redox storage emerging from a new pincer ligand upon bis-ligation of iron(ii) is described. When tetrazine arms are present at the two ortho positions of pyridine, the resulting bis-tetrazinyl pyridine (btzp) pincer ligand displays a single one-electron reduction at ca. -0.85 V vs. Ag/AgCl. Complexation to iron, giving the cation Fe(btzp)2 2+, shows no oxidation but four reduction waves in cyclic voltammetry instead of the two expected for the two constituent ligands. Mossbauer, X-ray diffraction and NMR studies show the iron species to contain low spin Fe(ii), but with evidence of back donation from iron to the pincer ligands. CV and UV-Vis spectroelectrochemistry, as well as titration studies as monitored by CV, electronic spectra and EPR reveal the chemical reversibility of forming the reduced species. DFT and EPR studies show varying degrees of delocalization of unpaired spin in different species, including that of a btzp-1 radical anion, partnered with various cations. This journal is the Partner Organisations 2014.
- Benson, Christopher R.,Hui, Alice K.,Parimal, Kumar,Cook, Brian J.,Chen, Chun-Hsing,Lord, Richard L.,Flood, Amar H.,Caulton, Kenneth G.
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- Syntheses of dual-radioisotope-labeled CP-I, a GABAA receptor partial agonist
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CP-I is a potent subtype-selective GABAA receptor partial agonist. Owing to its significant metabolic cleavage at C8 observed in preliminary biotransformation studies with non-radiolabeled CP-I, the syntheses of CP-I labeled at the right or left hand side with 14C or labeled with 3H at the right hand side were required. The two compounds labeled with 14C at the left or right hand side were synthesized in 2 and 5 radio-synthetic steps using [14C]2-chloroacetyl chloride and [ 14C]NaCN as starting radiolabeled materials, respectively. CP-I was labeled with tritium at the right hand side by a tritium de-halogenation method. Batches of radiolabeled CP-I were mixed to give dual-radioisotope-labeled CP-I. An efficient approach to [14C]fluoropyridinyl imidazole was developed, and a short synthesis of iodo-substituted fluoropyridinyl imidazole was also achieved. The details of these syntheses are discussed. Copyright
- Zhang, Yinsheng,Greenfield, Laura,Hong, Yang
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- Experimental and theoretical studies of a triazole ligand and complexes formed with the lanthanides
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The crystal structure of 2DBTZP·H2O [DBTZP = 2,6-bis(5-butyl-1,2,4-triazol-3-yl)pyridine] has been determined and shows a dimeric structure in which two ligands, with different protonation patterns, form four hydrogen bonds with an enclosed water molecule. Several crystal structures have been determined of lanthanide complexes with the corresponding 5-methyl derivative (DMTZP) which cover the lanthanide series. Four different structural types are reported: LaIII forms [La(DMTZP)(NO3)(H2O)5][NO3) 2; NdIII, SmIII and TbIII in the first part of the lanthanide series form [M(DMTZP)(NO3)3(H2O)] which is crystallographically disordered over a two-fold axis, HoIII forms [Ho(DMTZP)(NO3)3(H2O)], with one monodentate nitrate giving nine co-ordination, while ErIII and YbIII form [M(DMTZP)(NO3)3] complexes which are also nine-co-ordinate.
- Drew, Michael G. B.,Hudson, Michael J.,Iveson, Peter B.,Madic, Charles,Russell, Mark L.
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- An example of unusual pyridine donor Schiff base uranyl (UO22+) complexes
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The pentadentate coordination environment of a 2,6-bis[1-[(2-hydroxyphenyl)imino]ethyl] pyridine ligand scaffold was designed to accommodate the larger atomic radius of uranium as the uranyl dioxo cation, while fully occupying its equatorial plane. Here, two new uranyl (UO22+) complexes utilizing this scaffold have been synthesized from successive condensation reactions and subsequent metal complexation. Surprising Zn fluorescence is also discussed.
- Hardy,Wyss,Eddy,Gorden
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- Environmentally benign and economic synthesis of covalent triazine-based frameworks
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Covalent triazine-based frameworks (CTFs) are important microporous materials with a wide range of applications. Here, we demonstrate an environmentally benign and economic synthetic pathway to CTFs. The monomers used for CTFs, aromatic nitriles, were obtained by cyanation using nontoxic potassium hexacyanoferrate(II) in place of commonly used toxic cyanides. Then, the CTFs were synthesized by trimerization of the corresponding cyano monomers in molten zinc chloride. A series of CTFs was synthesized, and the highest Brunauer-Emmett-Teller surface area measured in this series was 2404 m2/g. Among the synthesized CTFs, CTFDCP exhibited excellent CO2 adsorption properties, with a CO2 uptake of 225 mg/g at 0 °C.
- Zhang, Ling,Liu, Xue,Yang, Rui-Xia,Huang, Nian-Yu,Deng, Wei-Qiao
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- Bis-(1,2,4-triazin-3-yl) ligand structure driven selectivity reversal between Am3+and Cm3+: solvent extraction and DFT studies
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Selectivity between Am3+and Cm3+was investigated after their aqueous complexation with three structurally tailored hydrophilic bis-(1,2,4-triazin-3-yl) ligands followed by their extraction withN,N,N′N′-tetraoctyl diglycolamide (TODGA) dissolved in an ionic liquid (C4mim·Tf2N). The three hydrophilic ligands used were SO3PhBTP, SO3PhBTBP, and SO3PhBTPhen. It was evident from the solvent extraction studies that SO3PhBTP formed a stronger complex with Cm3+than with Am3+, but SO3PhBTPhen showed better complexation ability for Am3+than for Cm3+, and SO3PhBTBP showed no selectivity for the two actinide ions. DFT calculations indicated that the coordinating ‘N’atoms in BTP were more co-planar in the complex and this co-planarity was higher in the Cm3+complex as compared to that in Am3+. In the case of BTBP and BTPhen ligands, on the other hand, the co-planarity was more pronounced in the Am3+complexes. Mayer's bond order calculations of M-N bonds in the complexes also indicated a reversal of the complexation ability of the BTP and BTPhen ligands for Am3+and Cm3+. Calculations of the complexation energies further supported the higher selectivity of the BTP ligand for Am3+by ?52.0 kJ mol?1, and better selectivity of the BTPhen ligand for Cm3+by ?24.7 kJ mol?1
- Ansari, S. A.,Bhattacharyya, Arunasis,Karthikeyan, N. S.,Mohapatra, P. K.,Rao, T. S.,Ravichandran, C.,Seshadri, H.,Venkatachalapathy, B.
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supporting information
p. 7783 - 7790
(2021/06/16)
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- Immobilized palladium nanoparticles on a cyclodextrin-polyurethane nanosponge (Pd-CD-PU-NS): An efficient catalyst for cyanation reaction in aqueous media
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Immobilized palladium nanoparticles on a cyclodextrin-polyurethane nanosponge (Pd-CD-PU-NS) were found to be an efficient heterogeneous catalyst in the cyanation reaction of aryl halides in aqueous media. This catalyst system is containing palladium nanoparticles with a size of ~7 nm. Moreover, the CD-PU-NS support formed microsphere-shaped structures with a size of ~100–200 nm. The TEM images show that Pd nanoparticles were formed in near spherical shape morphology and were immobilized in the structure of the CD-PU-NS support. Under our optimized reaction conditions, aryl cyanides were obtained in high yields in the presence of the Pd-CD-PU-NS catalyst. Our results demonstrated that the Pd-CD-PU-NS catalyst is highly effective in the cyanation reaction in aqueous media. Furthermore, the catalyst could be simply extracted from the reaction mixture, providing an efficient methodology for the synthesis of aryl cyanides. The Pd-CD-PU-NS catalyst could be recycled four times with almost consistent catalytic efficiency.
- Khajeh Dangolani, Soheila,Sharifat, Sara,Panahi, Farhad,Khalafi-Nezhad, Ali
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supporting information
p. 256 - 265
(2019/06/07)
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- Synthesis of bis(amidoxime)s and evaluation of their properties as uranyl-complexing agents
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Uranium pollution involves high toxicity and radioactivity and, therefore, constitutes a grave threat to human health and the environment. Chelation is an effective method for sequestering uranium. It is well known that chelators based on oxime groups are able to complex uranyl cations efficiently. To this end, various bis(amidoxime)s were synthesized by reaction of hydroxylamine with the corresponding dinitriles. In these compounds the amidoximes are separated by chains of various lengths, some including a heterocycle (pyridine or 1,3,5-triazine). The abilities of these bis(amidoxime)s to complex uranyl cation in water were evaluated by determining their affinity constants and thermodynamic parameters by means of Isothermal Titration Calorimetry (ITC). DFT calculations were also performed, to determine the optimum structures of the complexes formed between uranyl cations and the oximate groups. A tetrakis(amidoxime), also synthesized in this work, shows good affinity for uranium, and a single molecule is able chelate several uranyl cations. These results are of importance for the remediation of uranium-polluted wastewaters, and open up several perspectives for the design and synthesis of new amidoxime compounds.
- Stemper, Jérémy,Tuo, Wei,Mazarío, Eva,Helal, Ahmed S.,Djurovic, Alexandre,Lion, Claude,El Hage Chahine, Jean-Michel,Maurel, Fran?ois,Hémadi, Miryana,Le Gall, Thierry
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p. 2641 - 2649
(2018/04/20)
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- Pd-Metalated Conjugated Nanoporous Polycarbazoles for Additive-Free Cyanation of Aryl Halides: Boosting Catalytic Efficiency through Spatial Modulation
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Transition-metal-catalyzed cyanation of aryl halides is a common route to benzonitriles, which are integral to many industrial procedures. However, traditional homogeneous catalysts for such processes are expensive and suffer poor recyclability, so a heterogeneous analogue is highly desired. A novel spatial modulation approach has been developed to fabricate a heterogeneous Pd-metalated nanoporous polymer, which catalyzes the cyanation of aryl halides without need for ligands. The catalyst displays high activity in the synthesis of benzonitriles, including high product yields, excellent stability and recycling, and broad functional-group tolerance.
- Ding, Shunmin,Tian, Chengcheng,Zhu, Xiang,Abney, Carter W.,Tian, Ziqi,Chen, Bo,Li, Meijun,Jiang, De-En,Zhang, Ning,Dai, Sheng
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p. 2348 - 2351
(2017/06/13)
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- Preparation method of 2,6-dicyanopyridine
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The invention belongs to the technical field of chemical synthesis, and particularly relates to a preparation method of 2,6-dicyanopyridine. According to the method, pyridine-2,6-dicarboxylic acid, ammonia and phosphorus pentachloride have a dehydration reaction in an organic solvent, and 2,6-dicyanopyridine is obtained. According to the method, raw materials are easy to get, steps are short, and the cost is low.
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Paragraph 0016
(2016/11/17)
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- Synthesis of nitriles from aldehydes with trimethylphenylammonium tribromide and ammonium acetate
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Various aromatic and heterocyclic aldehydes were easily converted to respective nitriles with the combination of trimethylphenylammonium tribromide and ammonium acetate in good yields at room temperature.
- Sayama, Shinsei
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p. 1796 - 1802
(2016/11/06)
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- Electron-deficient heteroarenium salts: An organocatalytic tool for activation of hydrogen peroxide in oxidations
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A series of monosubstituted pyrimidinium and pyrazinium triflates and 3,5-disubstituted pyridinium triflates were prepared and tested as simple catalysts of oxidations with hydrogen peroxide, using sulfoxidation as a model reaction. Their catalytic efficiency strongly depends on the type of substituent and is remarkable for derivatives with an electron-withdrawing group, showing reactivity comparable to that of flavinium salts which are the prominent organocatalysts for oxygenations. Because of their high stability and good accessibility, 4-(trifluoromethyl)pyrimidinium and 3,5-dinitropyridinium triflates are the catalysts of choice and were shown to catalyze oxidation of aliphatic and aromatic sulfides to sulfoxides, giving quantitative conversions, high preparative yields and excellent chemoselectivity. The high efficiency of electron-poor heteroarenium salts is rationalized by their ability to readily form adducts with nucleophiles, as documented by low pKR+ values (pKR+ red > -0.5 V). Hydrogen peroxide adducts formed in situ during catalytic oxidation act as substrate oxidizing agents. The Gibbs free energies of oxygen transfer from these heterocyclic hydroperoxides to thioanisole, obtained by calculations at the B3LYP/6-311++g(d,p) level, showed that they are much stronger oxidizing agents than alkyl hydroperoxides and in some cases are almost comparable to derivatives of flavin hydroperoxide acting as oxidizing agents in monooxygenases.
- ?turala, Ji?í,Bohá?ová, Soňa,Chudoba, Josef,Metelková, Radka,Cibulka, Radek
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p. 2676 - 2699
(2015/03/18)
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- Engineering of osmium(II)-based light absorbers for dye-sensitized solar cells
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Panchromatic OsII sensitizers for dye-sensitized solar cells (DSCs) were prepared. A DSC based on TF-52 (see picture) showed promising performance characteristics: short-circuit photocurrent density J SC=23.3 mA cm-2, open-circuit photovoltage V OC=600 mV, fill factor (FF)=0.633, and power conversion efficiency =8.85 % under AM 1.5G simulated one-sun irradiation. Copyright
- Wu, Kuan-Lin,Ho, Shu-Te,Chou, Chun-Cheng,Chang, Yuh-Chia,Pan, Hsiao-An,Chi, Yun,Chou, Pi-Tai
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supporting information; scheme or table
p. 5642 - 5646
(2012/07/13)
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- Synthesis of optically active, unnatural α-substituted glutamic acid derivatives by a chiral calcium-catalyzed 1,4-addition reaction
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The first catalytic asymmetric 1,4-addition reactions of azlactones with acrylic esters have been developed. A chiral coordinative calcium catalyst was found to be effective for these reactions, and the desired 1,4-adducts were obtained in good yields and enantioselectivities. The product was converted to the corresponding α-alkylated glutamic acid by acid hydrolysis.
- Tsubogo, Tetsu,Kano, Yuichiro,Ikemoto, Koki,Yamashita, Yasuhiro,Kobayashi, Sh
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experimental part
p. 1221 - 1225
(2010/10/20)
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- Synthesis of dicyanopyridines
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Synthesis of the title compounds in four steps using inexpensive collidine and lutidine as starting materials is described.
- Roblou, Emmanuel,Sasaki, Isabelle,Pezet, Frederic,Ait-Haddou, Hassan,Vincendeau, Sandrine
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p. 3743 - 3749
(2007/10/03)
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- Site-Selectivity in the Cyanation of 3-Substituted Pyridine 1-Oxides with Trimethylsilanecarbonitrile
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The cyanation of 3-halo-, 3-methoxy-, and 3-dimethylaminopyridine 1-oxide with trimethylsilanecarbonitrile gave predominantly the corresponding 3-substituted 2-pyridinecarbonitriles.The deoxygenation of nitropyridine 1-oxides to nitropyridines with the same reagent is also described.Keywords - site-selective reaction; trimethylsilanecarbonitrile; pyridine 1-oxide; 2-pyridine-carbonitrile; nitropyridine 1-oxide; deoxygenation; aromatic amine N-oxide; cyanation
- Sakamoto, Takao,Kaneda, Soh-ichi,Nishimura, Sumiko,Yamanaka, Hiroshi
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p. 565 - 571
(2007/10/02)
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- Preparation of Macrocyclic Polyether-Thiono Diester and -Thiono Tetraester Ligands Containing either the Pyridine Subcyclic Unit or the Oxalyl Moiety, Their Complexes, and Their Reductive Desulfurization to Crown Ethers
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The preparation of seven new macrocyclic polyether-thiono diesters and one new macrocyclic polyether-thiono tetraester is reported.The new macrocyclic compounds containing a pyridine subcyclic unit formed complexes with metal and alkylammonium salts.Complex formation by some of these ligands was shown by variable-temperature 1H NMR spectroscopy and by cation transport through a CHCl3 membrane.All of the thiono compounds were reductively desulfurized to form the corresponding crown ethers.
- Jones, Brian A.,Bradshaw, Jerald S.,Brown, Philip R.,Christensen, James J.,Izatt, Reed M.
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p. 2635 - 2639
(2007/10/02)
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