- A family of hydrazone-based nucleosides for use in metal-mediated base pairs
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A new family of hydrazone-based nucleosides for use in metal-mediated base pairs was devised. The artificial nucleobases are derivatives of the papy ligand (papy = pyridinecarboxaldehyde-2′-pyridylhydrazone). By replacing the pendant pyridine moiety in papy by furan and thiophene, respectively, tridentate nucleosides with N, N, N-, N, N, O- and N, N, S-donor sites were obtained. As only a few transition metal complexes with pendant furan ligands have been reported, a model nucleobase for the N, N, O-donor nucleoside was synthesized. The molecular structures of its Cu2+, Ni2+, and Co 2+ complexes are reported. In all complexes, only weak M-O(furan) bonding is observed. The Co2+ complex displays a pentagonal bipyramidal coordination arrangement. In general, the structures of the metal complexes suggest that the respective nucleosides can be applied in metal-mediated base pairs. Copyright
- Radunsky, Christian,Megger, Dominik A.,Hepp, Alexander,Koesters, Jutta,Freisinger, Eva,Mueller, Jens
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- Chromogenic behaviour of a family of hydrazine and hydrazone metal complexes
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A family of five tridentate hydrazone-based ligands with an N,N,N-, N,N,O- or N,N,S-donor environment is reported. The tridentate ligands are derived from either 2-(1-methylhydrazinyl)pyridine or 2-hydrazinylpyridine and have been obtained by condensation with a series of aldehydes and ketones carrying one potential metal-binding site. To study their metal complexation behaviour, the five ligands and one of the bidentate precursor compounds have been reacted with ten different transition and main group metal ions. An interesting chromogenic behaviour has been found: ligands 1, 3 and H6 (with an N,N-, N,N,N- and N,N,O-donor environment) give very specific colour changes in the presence of Fe2+, whereas ligand H7 specifically forms a dark brown coloured complex with Co2+ only. All ligands form yellow to orange complexes with Pd2+. Three of these metal complexes were characterized by single-crystal X-ray diffraction analysis: the molecular structures of [Pd(1)Cl2], [Cu(1)Cl2]2, and [Cu(6)Cl] give an insight into the metal-binding behaviour of the ligands and nicely confirm the bidentate binding of ligand 1 and the tridentate binding of the deprotonated ligand 6-. It is proposed that the chromogenic behaviour of the ligands can be useful for the development of selective metal ion sensors.
- Radunsky, Christian,K?sters, Jutta,Müller, Jens
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- Metal transition complexes of tridentate Schiff base ligands derived from 2-hydrazinopyridine: synthesis, spectroscopic characterization and X-ray structures
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Mononuclear complexes of 1-(pyridin-2-ylmethylidene)-2-(pyridin-2-yl)hydrazine (HL1) and 1-(pyridin-2-yl)-2-(1-(pyridin-2-yl)ethylidene)hydrazine (HL2), [Mn(HL1)(Cl2)(H2O)] (1), [Zn(HL1)(CH3COO)2]·(H2O)3 (2), [Mn(HL2)2]·(ClO4)2 (3) and [Cu(HL2)(NO3)2(H2O)] (4) were synthesized and characterized by physicochemical and spectroscopic methods and X-ray structure determination. The mononuclear compounds 1, 2 and 4 contain one ligand molecule per metal atom while the manganese (II) atom in compound 3 is coordinated to two ligand molecules. Both ligands coordinated to the transition metal center in?a tridentate fashion through two Npyridyl atoms and one Nimino atom. The chloride and acetate anions coordinate in monodentate manner, respectively, in complex 1 and in complex 2. In complex 3, the perchlorate groups remain uncoordinated. In complex 4, the nitrate anions act in unidentate fashion. The molar conductance value indicates that the complexes obtained from HL1 are non-electrolytes while those obtained from HL2 are 2:1 electrolytes in DMF solutions. The X-ray structures reveal octahedral geometry for complexes 1, 3, 4 and trigonal bipyramidal environment for 2.
- Diop, Amar,Sarr, Mamou,Diop, Mayoro,Thiam, Ibrahima Elhadj,Barry, Aliou Hamady,Coles, Simon,Orton, James,Gaye, Mohamed
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- Manganese-Catalyzed Direct Olefination of Methyl-Substituted Heteroarenes with Primary Alcohols
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Herein, we present the first catalytic direct olefination of methyl-substituted heteroarenes with primary alcohols through an acceptorless dehydrogenative coupling. The reaction is catalyzed by a complex of the earth-abundant transition metal manganese that is stabilized by a bench-stable NNN pincer ligand derived from 2-hydrazinylpyridine. The reaction is environmentally benign, producing only hydrogen and water as byproducts. A large number of E-disubstituted olefins were selectively obtained with high efficiency.
- Barman, Milan K.,Waiba, Satyadeep,Maji, Biplab
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supporting information
p. 9126 - 9130
(2018/07/25)
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- Phosphine-Free NNN-Manganese Complex Catalyzed α-Alkylation of Ketones with Primary Alcohols and Friedl?nder Quinoline Synthesis
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Herein, we report a very simple and inexpensive catalytic system based on Earth's abundant transition metal manganese and on a bench-stable phosphine-free NNN-pincer ligand for an atom-efficient α-alkylations of ketones with primary alcohols via hydrogen-autotransfer C?C bond formation protocol. The precatalyst could be generated in situ and could be activated by using catalytic amount of base under milder conditions. A range of ketones were efficiently diversified with a broad range of primary alcohols in good to excellent isolated yields. Remarkably, this catalyst could also be employed for the synthesis of quinoline derivatives using 2-aminobenzyl alcohol as an alkylating agent. The later reaction is highly benign producing only hydrogen and water as byproducts. (Figure presented.).
- Barman, Milan K.,Jana, Akash,Maji, Biplab
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supporting information
p. 3233 - 3238
(2018/07/31)
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- Fac-Specific syntheses of homochiral [Fe(NN′)3] 2+ complexes (NN′ = pyridine keto-hydrazone); Origins of the stereoselectivity
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The 2-pyridinehydrazones (from condensation of pyridine-2-carbaldehyde and hydrazines) have previously been noted to have poor ligating ability as a result of a sterically demanding planar conformation. Destabilisation of this conformation is achieved through simple use of the ketohydrazones, and as a result the diamagnetic chiral tris-bidentate diimine complexes fac-[FeL 3]2+ are readily isolated. In the solid state, inter-ligand π-π stacking and complex/counter-ion H-bonding are apparent, and these features persist in solution according to dynamic NMR spectra, which also indicate extremely high stereoselectivity for the fac isomers (>200:1). The compounds crystallise as conglomerates, and time-resolved CD spectra of non-racemic samples indicate a high degree of persistence of chirality (racemisation t1/2ca 77 min). Variations of solvent and counter-ion indicate that H-bonding is unimportant in determining the structure of the cation. The fac-selectivity arises in the induction of a chiral conformation in the coordinated ligand, and the fact that such non-planar ligands can only be accommodated about the Fe(ii) centre if they all have the same absolute configuration. Adding a hydrazine N-methyl group increases the steric demand further, while retaining the novel non-planar conformation, and as a result paramagnetic chiral bis-bidentate complexes such as [FeL7 2(CH3CN)2]2+ are readily available.
- Sebli, Cynthia Paul,Howson, Suzanne E.,Clarkson, Guy J.,Scott, Peter
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experimental part
p. 4447 - 4454
(2010/07/04)
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- Medicinal uses of hydrazones
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Compounds having a structure according to Formula (I): are effective in a method of increasing erythropoietin and vascularization of tissue in a subject in need thereof.
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