- Catalytic Water Oxidation by a Molecular Ruthenium Complex: Unexpected Generation of a Single-Site Water Oxidation Catalyst
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The increasing energy demand calls for the development of sustainable energy conversion processes. Here, the splitting of H2O to O2 and H2, or related fuels, constitutes an excellent example of solar-to-fuel conversion schemes. The critical component in such schemes has proven to be the catalyst responsible for mediating the four-electron oxidation of H2O to O2. Herein, we report on the unexpected formation of a single-site Ru complex from a ligand envisioned to accommodate two metal centers. Surprising N-N bond cleavage of the designed dinuclear ligand during metal complexation resulted in a single-site Ru complex carrying a carboxylate-amide motif. This ligand lowered the redox potential of the Ru complex sufficiently to permit H2O oxidation to be carried out by the mild one-electron oxidant [Ru(bpy)3]3+ (bpy = 2,2′-bipyridine). The work thus highlights that strongly electron-donating ligands are important elements in the design of novel, efficient H2O oxidation catalysts. (Chemical Equation Presented).
- Rabten, Wangchuk,K?rk?s, Markus D.,?kermark, Torbj?rn,Chen, Hong,Liao, Rong-Zhen,Tinnis, Fredrik,Sun, Junliang,Siegbahn, Per E. M.,Andersson, Pher G.,?kermark, Bj?rn
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- Structural, spectroscopic and thermal characterization of 2-tert-butylaminomethylpyridine-6-carboxylic acid methylester and its Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and UO2(II) complexes
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Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and UO2(II) complexes with the ligand 2-tert-butylaminomethylpyridine-6-carboxylic acid methylester (HL2) have been prepared and characterized by elemental analyses, molar conductance, magnetic moment, thermal analysis and spectral data. 1:1 M:HL2 complexes, with the general formula [M(HL2)X 2]·nH2O (where M = Co(II) (X = Cl, n = 0), Ni(II) (X = Cl, n = 3), Cu(II) (grey colour, X = AcO, n = 1), Cu(II) (yellow colour, X = Cl, n = 0) and Zn(II) (X = Br, n = 0). In addition, the Fe(III) and UO 2(II) complexes of the type 1:2 M:HL2 and with the formulae [Fe(L2)2]Cl and [UO2(HL 2)2](NO3)2 are prepared. From the IR data, it is seen that HL2 ligand behaves as a terdentate ligand coordinated to the metal ions via the pyridyl N, carboxylate O and protonated NH group; except the Fe(III) complex, it coordinates via the deprotonated NH group. This is supported by the molar conductance data, which show that all the complexes are non-electrolytes, while the Fe(III) and UO2(II) complexes are 1:1 electrolytes. IR and H1-NMR spectral studies suggest a similar behaviour of the Zn(II) complex in solid and solution states. From the solid reflectance spectral data and magnetic moment measurements, the complexes have a trigonal bipyramidal (Co(II), Ni(II), Cu(II) and Zn(II) complexes) and octahedral (Fe(III), UO2(II) complexes) geometrical structures. The thermal behaviour of the complexes is studied and the different dynamic parameters are calculated applying Coats-Redfern equation.
- Mohamed, Gehad G.,El-Gamel, Nadia E.A.
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- Phenyl and pyridyl Bis-Pyrazoles: Synthesis from the Bis(p-diketone) precursors and characterization by analytical and spectroscopic methods
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The bis(β.-diketone) compounds, 3,3'-(pyridine-2,6-diyl)bis(1- phenylpropane-1,3-dione) monohydrated (1a-H2O) and 3,3'-(pyridine-2,6-diyl)bis(1-(pyridin-2-yl)propane-1,3-dione) monohydrated (1b-H2O) were prepared by Claisen condensation of the appropriate ketone and dimethyl pyridine-2,6-dicarboxylate ester. Compounds 2,6-bis(5- phenyl-17Y-pyrazol-3-yl)pyridine dihydrated (2a-2H2O) and 2,6-bis(5-(pyridin-2-yl)-17Y-pyrazol-3-yl)pyridine monohydrated (2b-H 2O) were synthesized by reaction of the appropriate bis(β.-diketone) compounds and hydrazine monohydrate.
- Pons, Josefina,Chadghan, Arafa,Garcia-Anton, Jordi,Ros, Josep
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- NMR and TRLFS studies of Ln(III) and An(III) C5-BPP complexes
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C5-BPP is a highly efficient N-donor ligand for the separation of trivalent actinides, An(iii), from trivalent lanthanides, Ln(iii). The molecular origin of the selectivity of C5-BPP and many other N-donor ligands of the BTP-type is still not entirely understood. We present here the first NMR studies on C5-BPP Ln(iii) and An(iii) complexes. C5-BPP is synthesized with 10% 15N labeling and characterized by NMR and LIFDI-MS methods. 15N NMR spectroscopy gives a detailed insight into the bonding of C5-BPP with lanthanides and Am(iii) as a representative for trivalent actinide cations, revealing significant differences in 15N chemical shift for coordinating nitrogen atoms compared to Ln(iii) complexes. The temperature dependence of NMR chemical shifts observed for the Am(iii) complex indicates a weak paramagnetism. This as well as the observed large chemical shift for coordinating nitrogen atoms show that metal-ligand bonding in Am(C5-BPP)3 has a larger share of covalence than in lanthanide complexes, confirming earlier studies. The Am(C5-BPP)3 NMR sample is furthermore spiked with Cm(iii) and characterized by time-resolved laser fluorescence spectroscopy (TRLFS), yielding important information on the speciation of trace amounts of minor complex species.
- Adam, Christian,Beele, Bj?rn B.,Geist, Andreas,Müllich, Udo,Kaden, Peter,Panak, Petra J.
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- Correction to: Dipicolinic acid derivatives as inhibitors of new delhi metallo-β-lactamase-1 (Journal of Medicinal Chemistry (2017) 60 (7267-72830 DOI: 10.1021/acs.jmedchem.7b00407)
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Page 7270. In Scheme 1, the compound numbers are mislabeled. Compound 11 should be compound 1, compound 12 should be 2, and compounds 13?30 should be 3?20. The mislabel of the compounds in the scheme does not affect the main text or the results of this paper. The corrected Scheme 1 is shown here. (Figure Presented).
- Chen, Allie Y.,Thomas, Pei W.,Stewart, Alesha C.,Bergstrom, Alexander,Cheng, Zishuo,Miller, Callie,Bethel, Christopher R.,Marshall, Steven H.,Credille, Cy V.,Riley, Christopher L.,Page, Richard C.,Bonomo, Robert A.,Crowder, Michael W.,Tierney, David L.,Fast, Walter,Cohen, Seth M.
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- Penipratynolene, a novel nematicide from Penicillium bilaiae Chalabuda
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New acetylenic nematicidal compound, penipratynolene (1), methy (2′R)-4-(2e-hydroxy-3e-butynoxy)benzoate, together with two known compounds, 6-methoxycarbonylpicolinic acid (2) and 2,6-pyridinedicarboxylic acid (3), were isolated from the culture filtrate of Penicillium bilaiae Chalabuda. The structures of 1-3 were established by spectroscopic methods. The absolute configuration of 1 was confirmed by using a modified version of Mosher's method. Compounds 1-3 showed nematicidal activity of 77%, 52%, and 98%, respectively, by a bioassay at 300 mg/l with the root-lesion nematode Pratylenchus penetrans.
- Nakahara, Satoshi,Kusano, Miyako,Fujioka, Shozo,Shimada, Atsumi,Kimura, Yasuo
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- Thermochemistry of a Cobalt Complex with Ionisable Pyrazole Protons
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Herein, we present the thermodynamic analysis of a cobalt complex with a new pentadentate N-donor ligand bearing four ionisable pyrazole protons in aqueous solution. A detailed analysis of the CoII complex [Co(L)(X)]+/2+ in the solid state revealed that the 6th ligand X at the metal centre depends on the cobalt source employed. Small anions such as Cl– and NO3– coordinate to the metal ion, while larger anions that are weaker hydrogen-bond acceptors are found in the second coordination sphere of the complex and instead a solvent molecule coordinates. However, in aqueous KCl solution, the sixth ligand is always chloride forming [Co(L)Cl]Cl, 1Cl. pH dependent species distribution studies revealed a pKa of 7.3(3) for the first ionisable pyrazole proton in the cobalt(II) complex and 6.0(3) in the cobalt(III) complex (methanol/H2O mixture). That is the oxidation state has a fairly minor influence on the pKa of the pyrazole proton. The CoIII/CoII redox pair of the complex with the fully protonated ligand exhibits a potential of 0.78 V vs. NHE. The BDFE of the hypothetical H-atom abstraction step of [CoII(L)Cl]+ forming [CoIII(LH–1)Cl]+ was determined to equal 336 kJ mol–1.
- Wilken, Mona,Würtele, Christian,Kügler, Merle,Chrobak, Frank,Siewert, Inke
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- Synthesis, characterization and fluorescence properties of Eu(III) and Tb(III) complexes with novel mono-substituted β-diketone ligands and 1,10-phenanthroline
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Two novel pyridine-2,6-dicarboxylic acid derivatives of mono-β-diketone, methyl 6-benzoylacetyl-2-pyridinecarboxylate (MBAP) and 6-benzoylacetyl-2-pyridinecarboxylic acid (BAPA) and their Eu(III) and Tb(III) complexes were synthesized and characterized by elemental analysis, FT-IR, 1H NMR and TG-DTG. Moreover, their Eu(III) and Tb(III) complexes using 1,10-phenanthroline as a secondary ligand were prepared and characterized. The luminescence properties of these complexes in solid state were investigated in detail. The results suggested that Tb(III) complexes exhibit more efficient luminescence than Eu(III) complexes, the fluorescence intensity of Ln(III) complexes with BAPA is about twice as strong as that of Ln(III) complexes with MBAP, the fluorescence of mono-β-diketone complexes using 1,10-phenanthroline as a secondary ligand was prominently higher than that of complexes without adding 1,10-phenanthroline, and the ligand BAPA is an excellent sensitizer to Eu(III) and Tb(III) ion.
- Luo, Yi-Ming,Li, Jun,Xiao, Lin-Xiang,Tang, Rui-Ren,Tang, Xin-Cun
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- A Photoswitchable Heteroditopic Ion-Pair Receptor
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Designing light-switchable heteroditopic receptors is challenging because it necessitates simultaneous (de)activation of two separate binding sites. Herein, we present the first photoswitchable heteroditopic ion-pair receptor in which both cation and anion binding sites are simultaneously and reversibly switched OFF and ON by a single photoswitch. Our receptor is simple, low molecular weight, and readily synthesized from commercially available precursors. Single-crystal X-ray structures and NMR spectroscopic titrations support ion-pair binding to the receptor both in the solid state and in solution, with strong positive cooperativity between the cation and anion binding. The receptor can be completely switched OFF by UV light-triggered photoisomerization of an acylhydrazone C=N double bond and remains kinetically stable in the deactivated form due to an intramolecular hydrogen bond. Its re-activation could be achieved by light irradiation or, more effectively, by fast acid-catalyzed back-isomerization. Our simple photoswitchable ion-pair receptor may serve as a blueprint for the design of new generations of switchable receptors, transporters, soft materials, and self-assembled systems, where incorporation of a functional heteroditopic ON/OFF photoswitch has been challenging up to now.
- Kokan, Zoran,Chmielewski, Micha? J.
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- Investigations into the bovine serum albumin binding and fluorescence properties of Tb (III) complex of a novel 8-hydroxyquinoline ligand
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A novel ligand, 2-methyl-6-(8-quinolinyl)-dicarboxylate pyridine (L), and its corresponding Tb (III) complex, Na4Tb(L)2Cl 4·3H2O, were successfully prepared and characterized. The luminescence spectra showed that the ligand L was an efficient sensitizer for Tb (III) luminescence. The interaction of the complex with bovine serum albumin (BSA) was investigated through fluorescence spectroscopy under physiological conditions. The Stern-Volmer analysis indicated that the fluorescence quenching was resulted from static mechanism. The binding sites (n) approximated 1.0 and this meant that interaction of Na 4Tb(L)2Cl4·3H2O with BSA had single binding site. The results showed van der Waals interactions and hydrogen bonds played major roles in the binding reaction. Furthermore, circular dichroism (CD) spectra indicated that the conformation of BSA was changed.
- Zhao, Mingming,Tang, Ruiren,Xu, Shuai
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- Ligand symmetry significantly affects spin crossover behaviour in isomeric [Fe(pybox)2]2+complexes
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The understanding of the correlation between the spin-state behaviour and the structural features in transition-metal complexes is of pronounced importance to the design of spin crossover compounds with high performance. However, the study of the influence of ligand symmetry on the spin crossover properties is still limited due to the shortage of suitable structural systems. Herein we report the magneto-structural correlations of three mononuclear Fe(ii) isomers with respect to their ligand symmetry. In this work, two phenyl-substitutedmesoandoptically purepybox ligands were employed to constructmeso(1),optically pure(2), andracemic(3) ligand types of [Fe(pybox)2]2+complexes. Their magnetic susceptibilities were measuredviatemperature-dependent paramagnetic1H NMR spectroscopy. We fitted the midpoint temperatures of the transition (T1/2) of 260 K for1(ClO4), 247 K for2(ClO4), and 281 K for3(ClO4). The influence of structural symmetry on spin crossover was rationalized through density functional theory calculations. The optimized structures of [Fe(pybox)2]2+complex cations show that the geometric distortion of the central FeN6coordination sphere is mainly caused by the steric congestions between adjacent phenyl substituents. In these compounds, there is a distinct correlation that more steric congestions produce larger coordination distortion and favor the electron configuration in the high-spin state, which reflects in the increase ofT1/2. Additionally, the influence of the counter anion and lattice solvent on themesoseries compounds was inspected. It is revealed that multiple factors dominate the spin-state behaviour in the solid state. This work provides deep insight into the effect of ligand symmetry on the spin transition behaviour in spin crossover compounds. It demonstrates that molecular symmetry should be considered in the design of spin crossover compounds.
- Wang, Run-Guo,Meng, Yin-Shan,Gao, Fang-Fang,Gao, Wan-Qing,Liu, Chun-Hua,Li, Anyang,Liu, Tao,Zhu, Yuan-Yuan
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- Effect of Oxygen-Donor Charge on Adjacent Nitrogen-Donor Interactions in Eu3+Complexes of Mixed N,O-Donor Ligands Demonstrated on a 10-Fold [Eu(TPAMEN)]3+Chelate Complex
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To reduce high-level radiotoxic waste generated by nuclear power plants, highly selective separation agents for minor actinides are mandatory. The mixed N,O-donor ligand N,N,N′,N′-tetrakis[(6-carboxypyridin-2-yl)methyl]ethylenediamine (H4TPAEN; 1) has shown good performance as a masking agent in Am3+/Eu3+ separation studies. Adjustments on the pyridyl backbone to raise the hydrophilicity led to a decrease in selectivity and a decrease in M3+-Nam interactions. An enhanced basicity of the pyridyl N-donors was given as a cause. In this work, we examine whether a decrease in O-donor basicity can promote the M3+-Nam interactions. Therefore, we replace the deprotonated "charged"carboxylic acid groups of TPAEN4- by neutral amide groups and introduce N,N,N′,N'-tetrakis[(6-N″,N′′-diethylcarbamoylpyridin-2-yl)methyl]ethylenediamine (TPAMEN; 2) as a new ligand. TPAMEN was crystallized with Eu(OTf)3 and Eu(NO3)3·6H2O to form positively charged 1:1 [Eu(TPAMEN)]3+ complexes in the solid state. Alterations in the M-O/N bond distances are compared to [Eu(TPAEN)]- and investigated by DFT calculations to expose the differences in charge/energy density distributions at europium(III) and the donor functionalities of the TPAEN4- and TPAMEN. On the basis of estimations of the bond orders, atomic charges spin populations, and density of states in the Eu and potential Am and Cm complexes, the specific contributions of the donor-metal interaction are analyzed. The prediction of complex formation energy differences for the [M(TPAEN)]- and [M(TPAMEN)]3+ (M3+ = Eu3+, Am3+) complexes provide an outlook on the potential performance of TPAMEN in Am3+/Eu3+ separation.
- Schnaars, Kathleen,Kaneko, Masashi,Fujisawa, Kiyoshi
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- Synthesis and photophysical properties of a highly luminescent EuIII-containing hybrid thin film
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A luminescent thin film, Eu@glass, has been prepared on the surface of glass substrates from a silylated diamidopyridyl ligand L and the complex [Eu(dbm)3(H2O)2] (Hdbm?=?dibenzoylmethane) via a sol–gel method. The Eu@glass exhibits intense red photoluminescence under the irradiation of near UV light with a quantum yield of 26%. Compared to the compound [Eu(dbm)3(H2O)2], the photoluminescence intensity of Eu@glass is dramatically enhanced, and the emission lifetime of EuIII(0.517?ms) is more than an order of magnitude longer.
- Liu, Xue,Bouwman, Elisabeth
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- Complexes of 2,6-bis[N-(2′-pyridylmethyl)carbamyl]pyridme: Formation of mononuclear complexes, and self-assembly of double helical dinuclear and tetranuclear copper(II) and trinuclear nickel(II) complexes
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The potentially pentadentate ligand 2,6-bis[N-(2′-pyridylmethyl) carbamyl]pyridine (H2L1), readily prepared from reaction of a diester of pyridine-2,6-dicarboxylic acid (H2dipic) and 2-aminomethylpyridine (ampy), shows limited tendency to form 1: 1 M: L complexes with labile metal ions, although [CuL1] and [NIL1] were observed as minor species, the latter characterized by a crystal structure analysis. A mononuclear complex formed with inert Co(III) was characterized by a crystal structure as the neutral 1: 2 complex [Co(L1)(HL 1)] with two ligands acting as tridentate ligands, one coordinated by the central pyridine and its two flanking deprotonated amido groups, and the other by the central pyridine, one amido and one terminal pyridine group, with the remaining poorly coordinating protonated amide remaining unbound along with other terminal pyridine groups. Fe(III) is known to form a symmetrical 1: 2 complex, but that complex is anionic due to binding of all four deprotonated amido groups; the unsymmetrical neutral Co(III) complex converts into a symmetrical anionic species only on heating for hours in aqueous base in the presence of activated carbon. The most remarkable tendency of H 2L1, however, is towards the formation of robust double helical complexes: a dinuclear Cu(II) complex [Cu2L2 1] forms, as well as a trinuclear Ni(II) complex [Ni 3(L1)2(OAc)2(MeOH)2]. Moreover, in the presence of added H2dipic, the tetranuclear complex [Cu4(L1)2(dipic)2(OH 2)2] is obtained. All helical complexes have been characterized by X-ray crystal structure analyses, and all crystals feature a racemic mixture of left- and right-handed double helices stabilized by inter-ligand π-stacking (inter-ring distances of 3.2-3.8 A) of ligands which each span several metal ions. Using the chelating ligand pentane-2,4-dione (acac), each of the two pairs of adjacent monodentate ligands in [Ni 3(L1)2(OAc)2(OH2) 2] have been shown to be available for substitution without destroying the helical structure, to form [Ni3(L1) 2(acac)2], also characterized by a crystal structure.
- Alcock, Nathaniel W.,Clarkson, Guy,Glover, Peter B.,Lawrence, Geoffrey A.,Moore, Peter,Napitupulu, Mery
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- Construction of SCO-Active Fe(II) Mononuclear Complexes from the Thio-pybox Ligand
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The development of new spin-crossover complexes provides novel promising switching materials with significant potential at the molecular level. Ter-imine-type molecules represent one of the important classes of ligands in creating SCO-active complexes. Herein we report a family of mononuclear Fe(II) SCO-active compounds constructed from a new type of ter-imine ligand named the thio-pybox ligand (2,6-bis(4,4-dimethyl-4,5-dihydrothiazol-2-yl)pyridine, L1). Through the variation of counteranions, some cases display complete SCO and with T1/2 near ambient temperature. Among them, annealed [FeII(L1)2](ClO4)2 [1(ClO4)] shows T1/2↓ and T1/2↑ as 319 and 349 K, respectively. The wide thermal hysteresis of ΔT = 30 K originated from the weak interaction between complex cations and counteranions in the crystal lattice. Impressively, its high-spin population can be increased considerably by annealing at high temperature. The metastable high-spin phase is stable in the successive magnetic measurements and would gradually relax to its initial state with high population of low-spin configuration at ambient temperature. In acetonitrile-diluted solution, 1(ClO4) still maintains SCO with an estimated T1/2 at 240 K. Differential scanning calorimetry discloses the structural phase at around 355 K in the first heating process and the increase in the high-spin population concomitant with annealing was also corroborated by 57Fe M?ssbauer measurements. Additionally, the influences on SCO by counteranion and ligand structure are investigated, which show that the fine tuning of complex structures can affect the behavior of the spin state significantly. Finally, magneto-structural correlation studies were performed on the structures of 1(ClO4) and its oxygen analogue at multiple temperatures. The analyses of some structural parameters, including terminal N···N donor separation, bite angle, patulous angle, and the root mean squared deviation indicate that the replacement of the oxygen atom with a sulfur atom can effectively improve the flexibility and release the steric strain and thus tune the SCO toward ambient temperature. Our research demonstrates the rational design of the ligand can lead to new SCO-active compounds with high performance.
- Gao, Wan-Qing,Liu, Chun-Hua,Liu, Qiang,Liu, Tao,Meng, Yin-Shan,Pan, Yao,Zhu, Yuan-Yuan
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- Tubular porous coordination polymer for selective adsorption of CO2
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Multidentate chelating ligand is of an important influence on the structure and property of a coordination polymer. We designed a multidentate bridging ligands, 6,6′-(([1,1′-biphenyl]-4,4′-diylbis(azanediyl))bis(carbonyl))dipicolinic acid (bpdp), based on pyridine-2,6-dicarboxylate groups. A porous coordination polymer, [Mn(bpdp)]?2.8DMF (1, DMF = N,N,-dimethylacetamide), was obtained via solvothermal reaction. The bpdp ligand chelates to the Mn2+ atoms in a N,O,O’-tridentate mode, and link Mn2+ atoms into a helical chain. Three of these helical chains, which are related by translational symmetry, are intertwined together forming a tube structure. The tubes are arranged in parallel with strong hydrogen bonds and π???π interactions formed between tubes and forming a stable and highly porous structure, which showed high selectivity for adsorbing CO2 over N2.
- Liu, Xing-Gui,Lu, Zhen-Zhong,Meng, Mei-Mei,Wang, Li-Fei,Xi, Ji-Ming,Xu, Yong-Kai,Zhang, Rui,Zhu, Rui
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- Spectroscopic characterization of dipicolinic acid and its photoproducts as thymine photosensitizers
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Dipicolinic acid (DPA), present in large amount in bacterial spores, has been proposed to act as an endogenous photosensitizer in spore photoproduct formation. The proposed mechanism involves a triplet-triplet energy transfer from DPA to thymine. However, up to now, no spectroscopic studies have been performed to determine the interaction between the endogenous compound and the nucleobase, probably due to its photolability in aqueous solutions. Here, triplet excited state properties of DPA are reported together with its bimolecular quenching rate constant by thymidine, kq of ca. 5.3 × 109 M?1 s?1. To run more reliable studies, a stable methyl ester derivative of DPA, which exhibits the same spectroscopic properties as the parent compound, is also described. Finally, DPA photoproducts are characterized. Studies of their triplet excited state properties have demonstrated that, interestingly, one of them is able to photosensitize thymidine triplet excited state formation.
- Lhiaubet-Vallet, Virginie,Lineros-Rosa, Mauricio,Miranda, Miguel A.,Nardi, Giacomo,Palumbo, Fabrizio
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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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- Electron transfer pathways in photoexcited lanthanide(iii) complexes of picolinate ligands
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A series of luminescent lanthanide(iii) complexes consisting of 1,4,7-triazacyclononane frameworks and three secondary amide-linked carbostyril antennae were synthesised. The metal binding sites were augmented with two pyridylcarboxylate donors yielding octadentate ligands. The antennae carried methyl, methoxymethyl or trifluoromethyl substituents in their 4-positions, allowing for a range of excited state energies and antenna electronic properties. The1H NMR spectra of the Eu(iii) complexes were found to be analogous to each other. Similar results were obtained in the solid-state by single-crystal X-ray crystallography, which showed the structures to have nine-coordinate metal ions with heavily distorted tricapped trigonal prismatic geometries. Steady-state and time-resolved luminescence spectroscopy showed that the antennae could sensitize both Tb(iii) and Eu(iii), however, quantum yields were lower than in other octadentate complexes lacking pyridylcarboxylate. Complexes with more electron-poor pyridines were less emissive even when equipped with the same antenna. The oxidation and reduction potentials of the antennae and the pyridinecarboxylates, respectively, were determined by cyclic voltammetry. The obtained values were consistent with electron transfer from the excited antenna to the pyridine providing a previously unexplored quenching pathway that could efficiently compete with energy transfer to the lanthanide. These results show the crucial impact that photophysically innocent ligand binding sites can have on lanthanide luminescence.
- Kovacs, Daniel,Kocsi, Daniel,Wells, Jordann A. L.,Kiraev, Salauat R.,Borbas, K. Eszter
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supporting information
p. 4244 - 4254
(2021/04/06)
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- Reductive N-methylation of alkanolamines with paraformaldehyde in the presence of cobalt catalysts
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Herein a simple method for N-methylation of ethanolamines with paraformaldehyde as a dual methylation and reducing agent has been investigated. Two new cobalt complexes, Co[Methyl 6-(morpoline methyl) picolinate]2Cl2 and Co(2,6 bis morpholine methyl pyridine)Cl2 were prepared and applied as homogeneous catalyst in reductive methylation reaction. All experiments have progressed with excellent conversion and selectivity toward N,N dimethyl ethanolamine. On the other hand, Pyrolysis of prepared cobalt complexes on activated carbon at 550 °C leads to the formation of cobalt oxide nano-particles. These heterogeneous catalysts were shown similar activities in this reaction. Single-crystal X-ray crystallography, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) were used for characterization of prepared catalysts.
- Dindar, Sara,Janczak, Jan,Nemati Kharat, Ali,Zamanian, Sara
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- Novel 2,6-disubstituted pyridine hydrazones: Synthesis, anticancer activity, docking studies and effects on caspase-3-mediated apoptosis
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Novel pyridine-based dihydrazones (3a-l) were synthesized by the condensation of appropriate aldehydes and pyridine-2,6-dicarbohydrazide (2) which was obtained by the treatment of dimethyl pyridine-2,6-dicarboxylate (1) with hydrazine hydrate. Structures of all the synthesized compounds were supported by their FTIR, 1H NMR, 13C NMR and microanalytical data. The compounds were screened primarily for their antibacterial activities as well as anticancer activities. None of the synthesized compounds had important antibacterial activity. Among the compounds which were tested against human colon cancer cell line (HT-29), compounds 3f and 3k showed significant activity (IC50=6.78 μM for compound 3f, IC50=8.88 μM for compound 3k). In addition, compound 3g exhibited promising activity against Ishikawa human endometrial cancer cell line (ISH) with an IC50 value of 8.26 μM. At 10 μM, compounds 3f, 3k and 3g caused morphological changes of HT-29 and ISH cells and caspase-3 activation. In addition, these compounds were evaluated against NIH 3T3 mouse embriyonic fibroblast cell line and all synthesized compounds (3a-l) were found to be less toxic than paclitaxel. Moreover, possible inhibition mechanism of compound 3g was evaluated in silico against BRAF kinase enzyme.
- ?evik, ?zge,?enkarde?, Sevil,Abbak, Mürüvvet,Durak, As?m Tu?rul,Ekrek, Sedanur,Güniz Kü?ükgüzel, ?.,Kü?ükgüzel, ?lkay,Ka?katepe, Banu,Türe, Asl?
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- Preparation method of 2,6-chloromethylpyridine hydrochloride (by machine translation)
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The invention belongs to the field, of organic synthesis, and particularly relates to 2,6 -chloromethylpyridine hydrochloride, preparation method :(1), which comprises the following steps 2,6 - reacting,dimethylaminopyridine as a raw material 2,6 - to prepare ;(2)2,6 -picolinic acid dimethyl 2,6 -picolinic acid dimethyl ;(3)2,6 -pyridine dimethanol and thionyl chloride to obtain a target product 2,6 -dichloromethylpyridine dihydrochloride with methanol in an acidic condition ;(4)2,6 - The method comprises the following steps: reacting 2,6 - with a commonly-used chemical raw material containing a pyridine ring and methanol in an acidic condition. The method disclosed by the invention is suitable for industrial, production : (by machine translation)
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- A light triggered optical and chiroptical switch based on a homochiral Eu2L3helicate
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Optical and chiroptical photoswitches have found potential applications in advanced information technologies. Herein, a pair of chiral triple-stranded helicates [Eu2(o-LRR)3](TOf)6and [Eu2(o-LSS)3](TOf)6, which have chirality, luminescence and light stimuli-responsive properties, have been designed and synthesized. The ligands o-LRR/SSare composed of photochromic diarylethene moieties as spacers and two chiral 2,6-dipicolinic amides as coordination units. Through the comprehensive spectral characteristics in combination with semiempirical geometry optimization using the Sparkle/RM1 model, it was confirmed that (R/S)-1-phenylethanamines decorated at the terminals of ligands successfully controlled the stereoselective self-assembly of the helicates. Upon alternating UV and visible light irradiation, the diarylethene experienced a reversible change between a colorless open-ring state and a pink closed-ring state. This photochromic process caused variations in the electronic structure and ligand conformation, and led to the presence of light-responsive optical (UV and PL) and chiroptical (ECD and CPL) switching properties. The helicate may, therefore, be considered as a completely reversible +/- ECD and on/off CPL switch. Furthermore, on the basis of these light-switchable optical properties, the INHIBIT and IMPLICATION logic gates were fabricated.
- Cheng, Zhenyu,Gao, Ting,Li, Hongfeng,Yan, Pengfei,Yao, Yuan,Zhang, Jianpeng,Zhou, Yanyan
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p. 6788 - 6796
(2020/06/03)
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- Gallium Fluoride Complexes with Acyclic Bispicolinic Ligands as Potential New Fluorine-18 Labelled Imaging Agents
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The positron-emitting radionuclide, fluorine-18, is used to radiolabel molecules to develop tracers for diagnostic imaging with positron-emission tomography. There is growing interest in the potential of using strong coordinate bonds between electropositive Ga(III) and electronegative fluoride (≈ 557 kJ/mol) to provide new methods of incorporating fluorine-18 into molecules. The potential of gallium(III) complexes with acyclic pentadentate bispicolinic acid containing ligands (H2L1–3) to form ternary complexes with fluoride, [GaL1–3F] was investigated with a view to developing new methods for fluorine-18 radiolabelling. A solid-phase peptide synthesis approach was used to produce a bispicolinic acid chelator with a lysine residue. Characterisation of [GaL1X] (X = OH, Cl, F) by X-ray crystallography revealed that L1 acted as dianionic N2O2 donor to the Ga(III) with the fifth site occupied by a monodentate anion (OH–, Cl– or F–). Despite its high stability in aqueous mixture and [D6]DMSO and the straightforward synthesis of [GaL1F], it was only possible to form the radioactive analogue [18F][GaL1F] in low radiochemical yields.
- Donnelly, Paul S.,Haskali, Mohammad B.,Koay, HuiJing,Roselt, Peter D.,White, Jonathan M.
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p. 3378 - 3386
(2020/09/12)
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- Chromogenic and fluorogenic "off-on-off" chemosensor for selective and sensitive detection of aluminum (Al3+) and bifluoride (HF2-) ions in solution and in living Hep G2 cells: Synthesis, experimental and theoretical studies
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A simple pyridine-dicarbohydrazide based colorimetric and fluorometric chemosensor L was designed and synthesized for Al3+ ion sensing in organo aqueous solution. In the presence of Al3+ ions, probe L exhibited visible color changes and fluorescence enhancement (20-fold) due to Al3+ induced chelation-enhanced fluorescence (CHEF) effects. Chemosensor L revealed high selectivity toward Al3+ ions by "turn-on"fluorescence among the other competitive metal ions examined with a detection limit of 0.8 μM. Probe L was found to bind with Al3+ ions in a 1 : 2 (probe : metal) stoichiometric fashion, with an association constant (Ka) of 4.26 × 104 M-2. In addition, DFT and TDDFT calculations were carried out to recognize the binding nature and electronic properties of probe L and its Al-complex. Furthermore, the in situ prepared [L-Al] complex was able to detect HF2- anions via a metal displacement strategy. The bioimaging application of Al3+ and HF2- was implemented in living human liver cancer cells (Hep G2). This journal is
- Manna, Saikat Kumar,Mondal, Debasish,Mukhopadhyay, Subrata,Pal, Kunal,Pathak, Sudipta,Pramanik, Samit
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p. 13259 - 13265
(2020/10/07)
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- Design, synthesis, and biological characterization of a new class of symmetrical polyamine-based small molecule CXCR4 antagonists
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CXCR4, a well-studied coreceptor of human immunodeficiency virus type 1 (HIV-1) entry, recognizes its cognate ligand SDF-1α (also named CXCL12) which plays many important roles, including regulating immune cells, controlling hematopoietic stem cells, and directing cancer cells migration. These pleiotropic roles make CXCR4 an attractive target to mitigate human disorders. Here a new class of symmetrical polyamines was designed and synthesized as potential small molecule CXCR4 antagonists. Among them, a representative compound 21 (namely HF50731) showed strong CXCR4 binding affinity (mean IC50 = 19.8 nM) in the CXCR4 competitive binding assay. Furthermore, compound 21 significantly inhibited SDF-1α-induced calcium mobilization and cell migration, and blocked HIV-1 infection via antagonizing CXCR4 coreceptor function. The structure-activity relationship analysis, site-directed mutagenesis, and molecular docking were conducted to further elucidate the binding mode of compound 21, suggesting that compound 21 could primarily occupy the minor subpocket of CXCR4 and partially bind in the major subpocket by interacting with residues W94, D97, D171, and E288. Our studies provide not only new insights for the fragment-based design of small molecule CXCR4 antagonists for clinical applications, but also a new and effective molecular probe for CXCR4-targeting biological studies.
- An, Jing,Fang, Xiong,Huang, Lina S.,Huang, Ziwei,Liang, Boqiang,Meng, Qian,Schooley, Robert T.,Wang, Juan,Xu, Yan,Zhang, Chaozai,Zhang, Huijun,Zhang, Xingquan,Zhu, Siyu
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supporting information
(2020/06/03)
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- A 2, 6 - dichloro methyl pyridine hydrochloride preparation method (by machine translation)
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The invention belongs to the field of organic synthesis, in particular relates to a 2, 6 - dichloro methyl pyridine hydrochloride of the preparation method, the method comprises the following steps: (1) to 2, 6 - lutidine as a raw material, preparation 2, 6 - pyridine dicarboxylic acid; (2) 2, 6 - pyridine dicarboxylic acid with methanol under acidic conditions to produce the 2, 6 - pyridine dicarboxylic acid dimethyl ester; (3) 2, 6 - pyridine dicarboxylic acid dimethyl ester is reduced to 2, 6 - pyridine-methanol; (4) 2, 6 - pyridine-methanol with thionyl chloride reaction to obtain the target product 2, 6 - dichloro methyl pyridine hydrochloride. The beneficial effect of the invention is: the invention adopts the commonly used chemical raw materials containing a pyridine [...] reaction, reaction steps is small, low cost, low toxicity, high yield, it is suitable for industrial production. (by machine translation)
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- TRACERS FOR PETROLEUM RESERVOIRS
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The disclosure features methods of analyzing a fluid extracted from a reservoir, the methods including introducing a first composition featuring a first complexing agent into a reservoir at a first location, extracting a fluid from the reservoir at a second location different from the first location, combining the fluid with a second composition featuring a concentration of a lanthanide ion to form a third composition featuring a concentration of a complex formed by the first complexing agent and the lanthanide ion, exposing a quantity of the complex to electromagnetic radiation for a first time period ending at a time to, detecting fluorescence emission from the quantity of the complex for a second time period starting at a time t1>t0, where t1?t0 is greater than 2 microseconds, and determining information about a fluid flow path between the first location and the second location.
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Paragraph 0590
(2019/08/02)
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- Small-molecules that covalently react with a human prolyl hydroxylase-towards activity modulation and substrate capture
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We describe covalently binding modulators of the activity of human prolyl hydroxylase domain 2 (PHD2) and studies towards a strategy for photocapture of PHD2 substrates. Reversible active site binding of electrophile bearing compounds enables susbsequent covalent reaction with a lysine residue (K408) in the flexible C-terminal region of PHD2 to give a modified protein that retains catalytic activity.
- Bush, Jacob T.,Le?niak, Robert K.,Yeh, Tzu-Lan,Belle, Roman,Kramer, Holger,Tumber, Anthony,Chowdhury, Rasheduzzaman,Flashman, Emily,Mecinovi?, Jasmin,Schofield, Christopher J.
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supporting information
p. 1020 - 1023
(2019/01/28)
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- Efficient Pincer-Ruthenium Catalysts for Kharasch Addition of Carbon Tetrachloride to Styrene
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A series of NNN pincer-ruthenium complexes (R2NNN)RuCl2(PPh3) (R=Cyclohexyl (Cy), t-butyl (tBu), i-propyl (iPr) and phenyl (Ph)) have been synthesized and characterized. These pincer-ruthenium complexes have been used to catalyse the Kharasch addition or atom transfer radical addition (ATRA) of carbon tetrachloride to styrene. Among the pincer-ruthenium catalysts screened for the Kharasch addition, the catalytic activity followed the order (Cy2NNN)RuCl2(PPh3)>(iPr2NNN)RuCl2(PPh3)?(Ph2NNN)RuCl2(PPh3). The oxidation of Ru(II) is easier with (Cy2NNN)RuCl2(PPh3) and (iPr2NNN)RuCl2(PPh3) in comparison with (Formula presented.) RuCl2(PPh3) as indicated by cyclic voltammetry studies. The catalyst precursor (R2NNN)RuCl2(PPh3) itself is the resting state of the reaction. The rate determining step involves the generation of the five-coordinate 16-electron ruthenium(II) species (R2NNN)RuCl2. Owing to weaker binding of triphenyl phosphine to ruthenium, the generation of catalytically active 16-electron species (Cy2NNN)RuCl2 and (iPr2NNN)RuCl2 are more favourable. The complex (Cy2NNN)RuCl2(PPh3) demonstrates very high productivity (5670 turnovers after 48 h at 140 °C) in the absence of any co-catalyst radical initiator. To the best of our knowledge, our turnovers (ca. 5670) are much higher than that reported hitherto. Quantum mechanical calculations demonstrate that the path involving the activation of carbon tetrachloride by (Cy2NNN)RuCl2 is more favoured than the path where carbon tetrachloride is activated by (Cy2NNN)RuCl2(η2-styrene). Density functional theory (DFT) and kinetic studies are in accord with the widely accepted mechanism involving the single electron transfer (SET) from ruthenium(II) to chloride radical with concomitant generation of a benzyl radical which is trapped by the resulting ruthenium(III) species. (Figure presented.).
- Das, Kanu,Dutta, Moumita,Das, Babulal,Srivastava, Hemant Kumar,Kumar, Akshai
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p. 2965 - 2980
(2019/04/30)
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- Nonanuclear Ni(II) complexes in a [1-7-1] formation derived from asymmetric multidentate ligands: Magnetic and electrochemical properties
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Nonanuclear Ni(ii) complexes, [Ni9(Ln)6(OH)6(H2O)6] (Ni9Ln, n = 1-4; H2Ln = 6-acetoacetyl-2-pyridinecarboxylic acid derivatives), were prepared via self-assembly using the asymmetric multidentate ligands H2Ln. A corner-sharing tetrahedron-type structure, [Ni7(μ3-OH)6]8+, and terminal mononuclear units constitute the nonanuclear structure in a [1-7-1] formation. The electrochemical and magnetic properties of Ni9Ln were modulated by the introduction of various substituents in H2Ln.
- Tsuji, Yasuhiro,Togo, Tatsuo,Mishima, Akio,Koshiyama, Tomomi,Ohba, Masaaki
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supporting information
p. 4036 - 4039
(2018/03/26)
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- PROCESSES FOR MAKING TRIAZOLO[4,5D] PYRAMIDINE DERIVATIVES AND INTERMEDIATES THEREOF
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Provided herein are, inter alia, methods for making triazolo[4,5]pyramidine derivatives and intermediates thereof that are useful for treating diseases.
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Paragraph 0332
(2018/10/25)
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- LANTHANIDE COMPLEXES FOR CRYSTALLISING BIOLOGICAL MACROMOLECULES AND DETERMINING THE CRYSTALLOGRAPHIC STRUCTURE THEREOF
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The invention relates to cationic complexes made up of a lanthanide ion Ln3+ and a ligand of formula (I) : with X, Y and R1 as defined in claim 1, and to the salts thereof with an anion, the solvates and hydrates thereof; with the exception of cationic complexes made up of a lanthanide ion Ln3+ and a ligand of one of formulae (I.1) or (I.4) as defined in claim 1, and the salts, solvates and hydrates thereof. The invention also relates to the use of such a complex or of a cationic complex made up of a lanthanide ion Ln3+ and a ligand of formula (I.1) or (I.4) as defined in claim 1, or of one of the salts thereof with an anion, the solvates or hydrates thereof, as an aid to the crystallisation of a biological macromolecule, as well as to crystallisation methods and methods for analysing or determining the structure of a biological macromolecule.
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Paragraph 0118; 0120; 0121; 0189
(2019/01/04)
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- Spin State Variations and Spin-Crossover in Diiron(II) Complexes of Bis(pentadentate) Pyrazolate-Based Ligands
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Compartmental pyrazolato-bridged ligands [LPy]? and [LIm]?, each providing two {N5} binding sites but differing in the terminal N-donors (pyridine vs. imidazole), were used to prepare a set of diferrous complexes; the ligand HLIm is new and its synthesis is reported. Complexes [LPyFe2(MeCN)2](OTf)3, (1OTf), [LPyFe2(MeCN)2](BF4)3 (1BF4), [LImFe{Fe(MeCN)}](OTf)3 (2OTf), and [LImFe{Fe(MeCN)}](BF4)3 (2BF4) were characterized by single-crystal X-ray diffraction, revealing a MeCN coligand at both (1OTf, 1BF4) or at only one (2OTf, 2BF4) of the two accessible Fe coordination sites that are directed into the bimetallic cleft. Magnetic measurements (SQUID) and 57Fe M??bauer spectroscopy indicate low-spin states for the six-coordinate FeII ions in 1OTf and 1BF4 that are based on [LPy]?, but two high-spin FeII ions in 2BF4 that is based on [LIm]?, in agreement with structural data. Complex 2OTf shows abrupt spin-crossover (SCO) from a mixed high-spin/low-spin to an all high-spin state at T? = 264 K, which appears to be correlated with the Fe–N≡C(Me) bonding angle. SCO, though gradual, is observed for 2OTf also in solution (T? = 273 K in MeCN, 248 K in EtCN), which was studied by M?ssbauer spectroscopy of frozen solution samples, variable temperature UV/Vis spectroscopy and SQUID magnetometry; the latter methods consistently gave thermodynamic parameters ΔH = 24.2 kJ·mol–1, ΔS = 89 J·mol–1·K–1 for the SCO of 2OTf in MeCN, and ΔH = 19.1 kJ·mol–1, ΔS = 77 J·mol–1·K–1 in EtCN.
- Schober, Anne,Demeshko, Serhiy,Meyer, Franc
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supporting information
p. 719 - 728
(2018/08/06)
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- REMOTE HETEROARYL ALKENYLATION WITH CATALYTIC BIFUNCTIONAL TEMPLATE
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We report the design of a catalytic, bifunctional template that binds heterocyclic substrate via reversible coordination instead of covalent linkage, allowing remote site- selective C-H olefination of heterocycles. The two metal centers coordinated to this template play different roles; anchoring substrates to the proximity of catalyst and cleaving the remote C-H bonds respectively. Using this strategy, we demonstrate remote site-selective C-H olefination of heterocyclic substrates which do not have functional group handles for covalently attaching templates. For instance the olefination can be an alkenylation of a 3- phenylpyridine with an acrylate alkyl ester selective for the meta position of the phenyl group with respect to the pyridine, or can be an alkenylation of a quinoline with an acrylate alkyl ester selective for the 5-position of the quinoline.
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Page/Page column 28
(2018/09/18)
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- Dicarbohydrazide based chemosensors for copper and cyanide ions: Via a displacement approach
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Ligands attached to pyridine dicarbohydrazide were synthesized and characterized by NMR, FT-IR, elemental analysis, UV-visible spectroscopy, mass spectrophotometry, emission spectra and single crystal X-ray diffraction. These ligands were found to recognize copper ions over other metal ions and cyanide ions by a copper complex performing an in situ experiment with turn on-off-on behaviour over different anions in a CH3OH:H2O (9:1, v/v solution) medium. These ligands displayed a red shift in their absorption spectra and quenching in their emission spectra when exposed to copper ions via a PET mechanism and a further copper complex was applied for cyanide detection among the other anions. The 1:2, 1:3, 1:2 and 1:2 stoichiometric ratios of the ligands (L1-L4, respectively) with copper ions were calculated from a Job plot based on the UV-visible spectra. The S-V plot represents the linearity of the ligands with copper ions. The limits of detection (LOD) of copper ions along with the ligands (L1-L4) were calculated to be 0.12, 0.10, 0.097 and 0.098 μM using emission spectra, respectively. The binding affinities of the ligands with copper ions were determined by various characterization techniques such as FTIR, mass spectrophotometry and electrochemical and optical studies. Furthermore, an in situ experiment was performed for cyanide detection via a metal displacement approach. L1 and L4 with Cu2+ ions showed an affinity towards cyanide ions, with detection limits of 0.31 and 0.53 μM.
- Yadav, Neetu,Singh, Ashok Kumar
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p. 6023 - 6033
(2018/04/23)
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- A chiral nitrogen - sulfur bidentate ligand and its synthetic method and application (by machine translation)
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The invention relates to a chiral nitrogen-sulfur bidentate ligand and a synthesis method and an application thereof. The chiral nitrogen-sulfur bidentate ligand is obtained by esterifying carboxylic acid firstly and then carrying out a reaction with chiral sulfinyl amine; the ligand is combined with a transition metal palladium, symmetrical allyl acetate is used as a substrate, dimethyl malonate and dimethyl fluoromalonate are used as nucleophilic reagents, and a chiral carbon-carbon bond is successfully constructed. Compared with the prior art, the chiral nitrogen-sulfur bidentate ligand has easily obtained synthetic raw materials, and the synthetic method is simple; the prepared chiral nitrogen-sulfur bidentate ligand is N-(sulphinyl)picolinamide with optical activity is applied in construction of the chiral carbon-carbon bond catalyzed by the transition metal palladium, the reaction conditions are mild, the operation is simple, in addition, the reaction yield is also better and is generally 78%-99%, and the enantioselectivity is high and has the highest value of 93%.
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Paragraph 0038; 0039; 0040; 0043; 0044
(2018/03/26)
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- Deoxygenation of tertiary amine N-oxides under metal free condition using phenylboronic acid
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A simple and efficient method for the deoxygenation of amine N-oxides to corresponding amines is reported using the green and economical reagent phenylboronic acid. Deoxygenation of N,N-dialkylaniline N-oxides, trialkylamine N-oxides and pyridine N-oxides were achieved in good to excellent yields. The reduction susceptible functional groups such as ketone, amide, ester and nitro groups are well tolerated with phenylboronic acid during the deoxygenation process even at high temperature. In addition, an indirect method for identification and quantification of tert-amine N-oxide is demonstrated using UV–Vis spectrometry which may be useful for drug metabolism studies.
- Gupta, Surabhi,Sureshbabu, Popuri,Singh, Adesh Kumar,Sabiah, Shahulhameed,Kandasamy, Jeyakumar
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supporting information
p. 909 - 913
(2017/02/15)
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- Synthesis of Esters by Functionalisation of CO2
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The invention relates to a method for (I) producing a carboxylic ester of formula (I). Said method comprises the steps of: a) bringing an organosilane/borane of formula Si or B into contact with CO2, in the presence of a catalyst and an electrophilic compound of formula (III), the groups R1, R2, R3, R4, R5, Y, and M′ being as defined in claim 1; and optionally b) recovering the compound of formula (I) produced.
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Paragraph 0129
(2017/09/06)
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- Dipicolinic Acid Derivatives as Inhibitors of New Delhi Metallo-β-lactamase-1
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The efficacy of β-lactam antibiotics is threatened by the emergence and global spread of metallo-β-lactamase (MBL) mediated resistance, specifically New Delhi metallo-β-lactamase-1 (NDM-1). By utilization of fragment-based drug discovery (FBDD), a new class of inhibitors for NDM-1 and two related β-lactamases, IMP-1 and VIM-2, was identified. On the basis of 2,6-dipicolinic acid (DPA), several libraries were synthesized for structure-activity relationship (SAR) analysis. Inhibitor 36 (IC50 = 80 nM) was identified to be highly selective for MBLs when compared to other Zn(II) metalloenzymes. While DPA displayed a propensity to chelate metal ions from NDM-1, 36 formed a stable NDM-1:Zn(II):inhibitor ternary complex, as demonstrated by 1H NMR, electron paramagnetic resonance (EPR) spectroscopy, equilibrium dialysis, intrinsic tryptophan fluorescence emission, and UV-vis spectroscopy. When coadministered with 36 (at concentrations nontoxic to mammalian cells), the minimum inhibitory concentrations (MICs) of imipenem against clinical isolates of Eschericia coli and Klebsiella pneumoniae harboring NDM-1 were reduced to susceptible levels.
- Chen, Allie Y.,Thomas, Pei W.,Stewart, Alesha C.,Bergstrom, Alexander,Cheng, Zishuo,Miller, Callie,Bethel, Christopher R.,Marshall, Steven H.,Credille, Cy V.,Riley, Christopher L.,Page, Richard C.,Bonomo, Robert A.,Crowder, Michael W.,Tierney, David L.,Fast, Walter,Cohen, Seth M.
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p. 7267 - 7283
(2017/09/22)
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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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supporting information
p. 5718 - 5720
(2017/07/11)
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- Improved synthesis of symmetrically & asymmetrically: N -substituted pyridinophane derivatives
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The N,N′-di(toluenesulfonyl)-2,11-diaza[3,3](2,6)pyridinophane (TsN4) precursor was sought after as a starting point for the preparation of various symmetric and asymmetric pyridinophane-derived ligands. Various procedures to synthesize TsN4 had been published, but the crucial problem had been the purification of TsN4 from the larger 18- and 24-membered azamacrocycles. Most commonly, column chromatography or other laborious methods have been utilized for this separation, yet we have found an alternate selective dissolution method upon protonation which allows for multi-gram scale output of TsN4·HCl. This optimized synthesis of TsN4 also led to the development of symmetric RN4 derivatives as well as the asymmetric derivative N-(tosyl)-2,11-diaza[3,3](2,6)pyridinophane (TsHN4). Using this TsHN4 precursor, different N-substituents can be added to create a library of asymmetric RR′N4 macrocyclic ligands. These asymmetric RR′N4 derivatives expand the utility of the RN4 framework in coordination chemistry and the ability to study the electronic, steric, and denticity effects of these pyridinophane ligands on the metal center.
- Wessel, Andrew J.,Schultz, Jason W.,Tang, Fengzhi,Duan, Hui,Mirica, Liviu M.
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p. 9923 - 9931
(2017/12/12)
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- Synthesis of Mono- and Dinuclear Vanadium Complexes and Their Reactivity toward Dehydroperoxidation of Alkyl Hydroperoxides
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Several vanadium(V) complexes with either dipic-based or Schiff base ligands were synthesized. The complexes were fully characterized by elemental analysis, IR, 1H, 13C, and 51V NMR spectroscopy, as well as mass spectrometry and X-ray diffraction. Furthermore, they were tested toward their catalytic deperoxidation behavior and a significant difference between 4-heptyl hydroperoxide and cyclohexyl hydroperoxide was observed. In the case of 4-heptyl hydroperoxide, the selectivity toward the corresponding ketone was higher than with cyclohexyl hydroperoxide. DFT calculations performed on the vanadium complex showed that selective decomposition of secondary hydroperoxides with vanadium(V) to yield the corresponding ketone and water is indeed energetically feasible. The computed catalytic path, involving cleavage of the O-O bond, hydrogen transfer, release of ketone/water, and finally addition of hydroperoxide, can proceed without the generation of radical species.
- Schmidt, Anna-Corina,Hermsen, Marko,Rominger, Frank,Dehn, Richard,Teles, Joaquim Henrique,Sch?fer, Ansgar,Trapp, Oliver,Schaub, Thomas
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supporting information
p. 1319 - 1332
(2017/02/15)
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- Synthesis, Resolution, and Absolute Configuration of Chiral Tris(2-pyridylmethyl)amine-Based Hemicryptophane Molecular Cages
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The synthesis, characterization, and chiroptical properties of a new class of hemicryptophane cages combining a cyclotriveratrylene unit and a tris(2-pyridylmethyl)amine (TPA) moiety are reported. Changing the linkers between these two units allows for the modification of the size and shape of the cavity. The synthesis is straightforward and efficient, providing gram-scale of cage compounds. The racemic mixture of each hemicryptophane host can be readily resolved by chiral HPLC, giving an easy access to the enantiopure molecular cages of which absolute configurations have been assigned by ECD spectroscopy. These new hemicryptophanes are available chemical platforms ready to use for various purposes due to the versatile metal complexation properties of the TPA unit. A Zn(II)@hemicryptophane complex has been obtained and used as a heteroditopic host for the selective recognition of zwitterionic guests.
- Zhang, Dawei,Bousquet, Benjamin,Mulatier, Jean-Christophe,Pitrat, Delphine,Jean, Marion,Vanthuyne, Nicolas,Guy, Laure,Dutasta, Jean-Pierre,Martinez, Alexandre
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p. 6082 - 6088
(2017/06/23)
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- General Cycloaddition between a Trimethylsilyl-Capped Alkyne and an Azide Catalyzed by an N-Heterocyclic Carbene-Copper Complex and Pyridine-Biscarboxamide
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With an externally provided catalytic amide facilitator and an N-heterocyclic carbene-copper (NHC-Cu) complex, the cycloaddition of an azide and a trimethylsilyl (TMS)-capped alkyne can proceed smoothly. This protocol can be applied to a variety of TMS-capped substrates, with electron-rich alkynes generally giving higher yields and nitroaromatic alkynes giving lower yields. For special applications of this protocol, a substrate containing both a terminal alkyne and a TMS-capped alkyne can sequentially react with different azides without isolation of intermediates; and a macrocyclic product can also be formed efficiently without the complication of polymer formation.
- Xu, Haochen,Sun, Zhihua
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supporting information
p. 1736 - 1740
(2016/06/09)
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- Catalyst-solvent interactions in a dinuclear Ru-based water oxidation catalyst
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Photocatalytic water oxidation represents a key process in conversion of solar energy into fuels and can be facilitated by the use of molecular transition metal-based catalysts. A novel straightforward approach for covalent linking of the catalytic units to other moieties is demonstrated by preparation of a dinuclear complex containing two [Ru(pdc)(pic)3]-derived units (pdc = 2,6-pyridinedicarboxylate, pic = 4-picoline). The activity of this complex towards chemical and photochemical oxidation of water was evaluated and a detailed insight is given into the interactions between the catalyst and acetonitrile, a common co-solvent employed to increase solubility of water oxidation catalysts. The solvent-induced transformations were studied by electrochemical and spectroscopic techniques and the relevant quantitative parameters were extracted.
- Shatskiy, Andrey,Lomoth, Reiner,Abdel-Magied, Ahmed F.,Rabten, Wangchuk,Laine, Tanja M.,Chen, Hong,Sun, Junliang,Andersson, Pher G.,K?rk?s, Markus D.,Johnston, Eric V.,?kermark, Bj?rn
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supporting information
p. 19024 - 19033
(2016/12/09)
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- CO2 Conversion into Esters by Fluoride-Mediated Carboxylation of Organosilanes and Halide Derivatives
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A one-step conversion of CO2 into heteroaromatic esters is presented under metal-free conditions. Using fluoride anions as promoters for the C-Si bond activation, pyridyl, furanyl, and thienyl organosilanes are successfully carboxylated with CO2 in the presence of an electrophile. The mechanism of this unprecedented reaction has been elucidated based on experimental and computational results, which show a unique catalytic influence of CO2 in the C-Si bond activation of pyridylsilanes. The methodology is applied to 18 different esters, and it has enabled the incorporation of CO2 into a polyester material for the first time. Metal free! A novel methodology is described to convert CO2 into heteroaromatic esters in the presence of organosilanes and organic halides using fluoride anions as promoters for the C-Si bond activation (see scheme). CO2 exhibits a unique catalytic influence in the C-Si bond cleavage of pyridylsilanes, serving as a traceless activator.
- Frogneux, Xavier,Von Wolff, Niklas,Thuéry, Pierre,Lefèvre, Guillaume,Cantat, Thibault
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supporting information
p. 2930 - 2934
(2016/03/25)
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- A Modular Synthesis of Multidentate S-, N- and O-Containing Meta- and Paracyclophanes
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The development of a modular approach to macrocycle assembly has enabled the synthesis of a library of pyridine-based macrocycles possessing multiple donor sites where chirality was readily introduced from (R)- or (S)-alanine, a representative amino acid. The facile, regioselective, nucleophilic ring opening of aziridines by dithiols enabled the synthesis of thioether-based linkers which on subsequent alkylation provided access to optically pure macrocycles. A modular approach to macrocyclic assembly has enabled the synthesis of a library of macrocycles possessing multiple donor sites where chirality was readily introduced from (S)-alanine. Key to this approach was the facile, regioselective, nucleophilic ring opening of aziridines by dithiols followed by macrocylisation under conditions of high dilution.
- Rasheed, Omer K.,Bailey, Patrick D.,Lawrence, Amy,Quayle, Peter,Raftery, James
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supporting information
p. 6988 - 6993
(2015/11/16)
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- Structural phase transition in a multi-induced mononuclear FeII spin-crossover complex
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Herein, we report the investigation of a mononuclear spin-crossover complex [FeIIL2][ClO4]2 (L = 2,6-bis{4,4-dimethyl-4,5-dihydrooxazol-2-yl}pyridine). This compound undergoes a structural phase transition around 173 K, accompanying with an abrupt spin-transition process. Interestingly, it exhibits a multi-induced spin-crossover behavior mediated by heat, light, pressure and solvent.
- Zhu, Yuan-Yuan,Liu, Chang-Wei,Yin, Ji,Meng, Zhao-Sha,Yang, Qian,Wang, Junhu,Liu, Tao,Gao, Song
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supporting information
p. 20906 - 20912
(2015/12/11)
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- Enantioselective fluorination of β-ketoesters catalysed by complexes of new mono-oxazoline ligands
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A new kind of mono-oxazoline ligands which combined diaryl methyl units and chiral oxazoline units together using pyridine as linker was prepared. Their applications in enantioselective electrophilic fluorination of β-ketoesters by NFSI were investigated, and the corresponding products were obtained in excellent yield (up to 90%) and good enantioselectivity (78%) in CH2Cl2 at -60 °C.
- Niu, Teng,Han, Xiping,Huang, Danfeng,Wang, Ke-Hu,Su, Yingpeng,Hu, Yulai,Fu, Ying
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supporting information
p. 6 - 11
(2015/03/31)
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- Separation of Am (III) by solvent extraction using water-soluble H4tpaen derivatives
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The water-soluble ligand N,N,N′,N′-tetrakis[(6-carboxypyridin-2-yl)methyl]ethylenediamine (H4tpaen) and its derivatives were synthesized and evaluated for Am/Cm separation by solvent extraction. In this context, different ligands were studied for their possible use as selective back-extraction agents of actinides, especially americium, from an organic TPH phase. The solvent consisted of different extractants mixtures (DMDOHEMA/HDEHP or TODGA/TBP systems) and was preliminarily loaded with trivalent lanthanide and actinide cations. The aim of these new water-soluble agents was to strip americium or curium in an aqueous acidic phase in order to perform their mutual separation while maintaining other cations in the organic phase. A specific ligand bearing n-alkoxy groups connected to the pyridyl rings of H4tpaen showed water solubility slightly enhanced associated with efficient back-extraction properties with the possibility to perform simultaneously inter-group separation of Am (III) from Eu (III), and intra-group separation of Am(III) from Cm(III).
- Gracia, Stéphanie,Arrachart, Guilhem,Marie, Cécile,Chapron, Simon,Miguirditchian, Manuel,Pellet-Rostaing, Stéphane
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p. 5321 - 5336
(2015/07/15)
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- Synthesis, characterization, and mechanism studies of bis(imino)pyridine ligands and their Cr(III) compounds
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Two new bis(imino)pyridine ligands L1, L2 (L1 = 2,6-bis[1-(4-bromophenylimino)]pyridine, L2 = 2,6-bis[1-(4-methylphenylimino)]pyridine) have been prepared. Their compounds [CrCl3L1] (I) and [Cr(Cl)(μ-Cl)(L2′)]2 (II) (L2′ = 6-bis(6-methylquinoline)pyridine) for olefin oligomerization were obtained by hydrothermal methods, during which L2′ was appeared from L2, and characterized by elemental analysis, single-crystal X-ray analysis (CIF files CCDC nos. 1025448 (I),1025447 (II)), IR spectra and melting point test. Compound I is a mononuclear compound, while compound II, bridged with the chlorine atoms, is a binuclear compound. The transformation mechanism between L2 and L2′ is also studied, and the possible reason is due to the presence of the electron-donating groups as substituents on L2. The subsequent studies on that will be carried on.
- Li, S. W.,Wang, Y. F.,Li, X. P.,Zhao, J. S.,Wang, J. L.
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p. 129 - 134
(2015/04/14)
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- Cation-Transporting Peptides: Scaffolds for Functionalized Pores?
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Protein pores that selectively transport ions across membranes are among nature's most efficient machines. The selectivity of these pores can be exploited for ion sensing and water purification. Since it is difficult to reconstitute membrane proteins in their active form for practical applications it is desirable to develop robust synthetic compounds that selectively transport ions across cell membranes. One can envision tuning the selectivity of pores by incorporating functional groups inside the pore. Readily accessible octapeptides containing (aminomethyl)benzoic acid and alanine are reported here that preferentially transport cations over halides across the lipid bilayer. Ion transport is hypothesized through pores formed by stable assemblies of the peptides. The aromatic ring(s) appear to be proximal to the pore and could be potentially utilized for functionalizing the pore interior.
- Behera, Harekrushna,Ramkumar, Venkatachalam,Madhavan, Nandita
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supporting information
p. 10179 - 10184
(2015/07/07)
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- SUBSTITUTED HETEROARYL ALDEHYDE COMPOUNDS AND METHODS FOR THEIR USE IN INCREASING TISSUE OXYGENATION
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Provided are substituted heteroaryl aldehydes and derivatives thereof that act as allosteric modulators of hemoglobin, methods and intermediates for their preparation, pharmaceutical compositions comprising the modulators, and methods for their use in treating disorders mediate by hemoglobin and disorders that would benefit from increased tissue oxygenation.
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Paragraph 0614; 0615
(2015/12/25)
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- Folding Patterns in a Family of Oligoamide Foldamers
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A series of small, unsymmetrical pyridine-2,6-dicarboxylamide oligoamide foldamers with varying lengths and substituents at the end groups were synthetized to study their conformational properties and folding patterns. The @-type folding pattern resembled the oxyanion-hole motifs of enzymes, but several alternative folding patterns could also be characterized. Computational studies revealed several alternative conformers of nearly equal stability. These folding patterns differed from each other in their intramolecular hydrogen-bonding patterns and aryl-aryl interactions. In the solid state, the foldamers adopted either the globular @-type fold or the more extended S-type conformers, which were very similar to those foldamers obtained computationally. In some cases, the same foldamer molecule could even crystallize into two different folding patterns, thus confirming that the different folding patterns are very close in energy in spite of their completely different shapes. Finally, the best match for the observed NOE interactions in the liquid state was a conformation that matched the computationally characterized helix-type fold. Erase and refold: Like peptides, oligoamide foldamers fold into a number of different conformers that are very close in energy (see picture, stability energies in kcal mol-1 given in parentheses). By using a combination of computational, single-crystal X-ray diffraction, and NMR spectroscopic studies, these folding patterns have been identified and characterized for a family of seven different foldamers with varying substituents.
- Kortelainen, Minna,Suhonen, Aku,Hamza, Andrea,Pápai, Imre,Nauha, Elisa,Yliniemel?-Sipari, Sanna,Nissinen, Maija,Pihko, Petri M.
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supporting information
p. 9493 - 9504
(2015/06/30)
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- Enantioselective synthesis of monofluorinated allylic compounds: Pd-catalyzed asymmetric allylations of dimethyl 2-fluoromalonate using new N-sulfinyl-based ligands
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New chiral S,N- and S,P-ligands starting from tert-butanesulfinamide were synthesized in four steps, applying Pd-catalyzed asymmetric allylic substitutions of dimethyl 2-fluoromalonate. The induced effect of the Pd/S,N-ligand catalyst on the enantioselectivity depends on the steric demand of the substituent at the o-position of the pyridine ring. This method produced monofluorinated allylation products in up to high yield with high enantioselectivity.
- Gao, Ning,Zhao, Xiao-Ming,Cai, Cheng-Si,Cai, Jue-Wang
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p. 9551 - 9558
(2015/09/28)
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