- [ONN]-type amine pyridine(s) phenolate-based oxovanadium(v) catalysts for ethylene homo- and copolymerization
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A series of oxovanadium(v) complexes containing amine pyridine(s) phenolate ligands [ONN] (2a-f) have been synthesized in high yields (68-83%) by reacting VO(OnPr)3 with 1.0 equiv. of the ligands in CH 2Cl2. The
- Wang, Jia-Bao,Lu, Ling-Pan,Liu, Jing-Yu,Li, Yue-Sheng
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Read Online
- There is nothing wrong with being soft: Using sulfur ligands to increase axiality in a Dy(iii) single-ion magnet
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A new air-stable sulfur-ligated Dy(iii) single-ion magnet has been successfully isolated with Ueff = 638 K and hysteresis loops open up to 7 K. In silico studies show that the S co-ligands significantly boost the axiality and that Te- and Se-donors have the potential to further enhance the magnetic properties.
- Canaj, Angelos B.,Dey, Sourav,Céspedes, Oscar,Wilson, Claire,Rajaraman, Gopalan,Murrie, Mark
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Read Online
- Scrabbling around in Synthetic Nuances Managing Sodium Compounds: Bisphenol/Bisnaphthol Synthesis by Hydroxyl Group Masking
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A unique method of bisphenol/bisnaphthol synthesis is being proposed, serendipitously discovered in the course of the careful analysis of an aminophenol methylation reaction. The insightful exploration of the synthesis of N- or O-methylated species, originating from functionalized phenols obtained by a conventional strategy, provided the opportunity to discover an unexpected reaction pathway yielding various bisphenols. Sodium complexes were found to be crucial intermediates in the synthetic scenario. Their formation, which is usually an imperceptive step, was substantial for the productive outcome of functional group protection. Thorough exploration revealed an essential structural motif of aminophenolate, necessary for the successful outcome of the reaction, and also enabled establishing the limitations of the new method. The work demonstrated that a slight change in the perspective and close inspection of the synthetic nuances can answer the important question concerning what a specific target-oriented synthesis strategy is lacking.
- Ejfler, Jolanta,J?drzkiewicz, Dawid,Marsza?ek-Harych, Aleksandra,Trybu?a, Danuta
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- Configurationally flexible zinc complexes as catalysts for rac-lactide polymerisation
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Zn(N(SiMe3)2)2 was reacted with pyridinemethanol and R,R-N,N′-di(methylbenzyl)-2,5-diiminopyrrole (L1H) to afford the dimeric complex (L1)2Zn2(μ-OR)2. The complex showed moderate activity i
- Daneshmand, Pargol,Michalsky, Ina,Aguiar, Pedro M.,Schaper, Frank
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p. 16279 - 16291
(2018/11/27)
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- Zinc and cobalt complexes based on tripodal ligands: Synthesis, structure and reactivity toward lactide
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The coordination chemistry of a series of pro-ligands ([L 1]-[L6]) with cobalt and zinc derivatives has been studied. All complexes have been characterized by multinuclear NMR, elemental analysis, and by single-crystal X-ray diffraction studies. Polymerization of rac-lactide takes place at 130°C in the presence of cobalt and zinc complexes to yield polymers under solvent free conditions with controlled molecular masses and narrow polydispersities.
- Tschan, Mathieu J.-L.,Guo, Jia,Raman, Sumesh K.,Brule, Emilie,Roisnel, Thierry,Rager, Marie-Noelle,Legay, Remi,Durieux, Guillaume,Rigaud, Baptiste,Thomas, Christophe M.
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p. 4550 - 4564
(2014/03/21)
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- The functional model complex [Fe2(BPMP)(OPr)(NO) 2](BPh4)2 provides insight into the mechanism of flavodiiron NO reductases
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Flavodiiron nitric oxide reductases (FNORs), found in many pathogenic bacteria, are able to detoxify NO by reducing it to N2O. In this way, FNORs equip these pathogens with immunity to NO, which is a central immune defense agent in humans. Hence, FNORs are thought to promote infection of the human body, leading to chronic diseases. Despite this importance of FNORs for bacterial pathogenesis, the mechanism of NO reduction by these enzymes is not well understood. Here we present the synthesis and spectroscopic characterization of the diiron dinitrosyl model complex [Fe2(BPMP) (OPr)(NO)2](BPh4)2. The crystal structure of this complex shows two end-on-coordinated {FeNO}7 units that, based on spectroscopic and electrochemical results, are only weakly electronically coupled. Importantly, reduction of this complex by two electrons leads to the clean formation of N2O in quantitative yield. This complex therefore represents the first example of a functional model system for FNORs. The results provide key mechanistic insight into the mechanism of FNORs and, in particular, represent strong support for the proposed super-reduced mechanism for these enzymes.
- Zheng, Sheng,Berto, Timothy C.,Dahl, Eric W.,Hoffman, Melissa B.,Speelman, Amy L.,Lehnert, Nicolai
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supporting information
p. 4902 - 4905
(2013/06/05)
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- Mononuclear iron(III) complexes supported by tripodal N3O ligands: Synthesis, structure and reactivity towards DNA cleavage
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A new synthetic route to the known tripodal tetradentate N3O ligand L1 (HL1 = [N-(3,5-di-tert-butyl-2-hydroxybenzyl)-N,N-di-(2-pyridylmethyl)]amine) is reported. The related compounds HLn (n = 2, 3) were prepared by a similar procedure. Treatment of HLn (n = 1-3) with FeCl3·6H2O in hot methanol led to the mononuclear iron(III) complexes [Fe(Ln)Cl2] (1: n = 1, 2: n = 2, 3: n = 3). The solid-state structures of complexes 1 and 2 were determined by X-ray crystallography. [Fe(L1)Cl2] (1) showed effective nuclease activity in the presence of hydrogen peroxide, converting supercoiled plasmid DNA to its linear form.
- Wong, Yee-Lok,Mak, Chun-Yin,Kwan, Hoi Shan,Lee, Hung Kay
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experimental part
p. 1246 - 1253
(2010/07/05)
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- Zinc and enolato-magnesium complexes based on bi-, tri- and tetradentate aminophenolate ligands
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The coordination chemistry of a series of potentially tetra-, tri- and bi-dentate aminophenol pro-ligands ([L1]H-[L5]H) with magnesium and zinc derivatives has been studied. Reactions of the pro-ligands [L1]H, [L2]H and [L3]H with one equiv. of ZnEt2 or Zn(N(SiMe3)2)2 in toluene at room temperature afford cleanly, via ethane or amine elimination, the ethyl- and amido-zinc complexes 1-4. Complexes [L4]ZnEt (5) and [L 4]Zn(N(SiMe3)2)2 (6) derived from the tridentate pro-ligand [L4]H were prepared in 84% and 76% yields, following similar alkane and amine elimination protocols, respectively. The 1:1 reactions of bidentate pro-ligand [L5]H with ZnEt2 or Zn(N(SiMe3)2)2 in toluene using different reaction protocols systematically yielded mixtures of the bis(ligand) complex [L5]2Zn (7) and the corresponding ethyl-{[L 5]ZnEt}n (8; n = 1 or 2) or amido- {[L5] Zn(N(SiMe3)2)}n complexes (9; n = 1 or 2). The synthesis of magnesium-enolate complexes 10 and 11 was carried out in a one-pot, two-step procedure by first reacting pro-ligands [L1]H and [L 4]H with one equiv. of Mg(n,sBu)2 to generate the corresponding {[Ln]Mg(n,sBu)}n species, which were further reacted with one equiv. of 2,4,6-Me3C6H2COMe. All complexes have been characterized by multinuclear NMR, elemental analysis, and by single-crystal X-ray diffraction studies for five-coordinate magnesium complex 10, and four-coordinate Zn complexes 3-7. Preliminary studies indicate that magnesium species 10 and 11 as well as zinc complexes 1 and 5 are not active initiators for the polymerization of methyl methacrylate, even in combination with one equiv. of Li[OC(=CH2)(2,4,6-Me3C 6H2)], while zinc complexes 2, 4 and 6 are effective initiators for the ring-opening polymerization of ε-caprolactone and rac-lactide at 20°C. The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2008.
- Zheng, Zhanjiang,Zhao, Gang,Fablet, Remy,Bouyahyi, Miloud,Thomas, Christophe M.,Roisnel, Thierry,Casagrande Jr., Osvaldo,Carpentier, Jean-Francois
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experimental part
p. 2279 - 2291
(2009/03/11)
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- Galactose oxidase models: Tuning the properties of Cu II-phenoxyl radicals
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Four tripodal ligands with an N3O coordination sphere were synthesized: (2-hydroxy-3-tert-butyl-5-nitrobenzyl)bis(2-pyridylmethyl)amine (LNO2H), (2-hydroxy-3-tert-butyl-5-fluorobenzyl)bis(2-pyridylmethyl)amine (LFH), (2-hydroxy-3,5-d
- Philibert, Aurelie,Thomas, Fabrice,Philouze, Christian,Hamman, Sylvain,Saint-Aman, Eric,Pierre, Jean-Louis
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p. 3803 - 3812
(2007/10/03)
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- Chemical approach to the Cu(II)-phenoxyl radical site in galactose oxidase: Dependence of the radical stability on N-donor properties
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Copper(II) complexes of several new N3O-type tripodal ligands, 2,4- di(t-butyl)-6-{[bis(2-pyridyl)methyl]amino-methyl}phenol (HtbuL), 2,4-di(t- butyl)-6-{[(6-methyl-2-pyridyl)methyl](2-pyridylmethyl)aminomethyl}phenol (HtbuL-(Mepy)), 2,4-di(t-butyl)-6-methyl-2-pyridyl)methyl]aminomethyl}phenol (HtbuL(Mepy)2), and 2,4-di(t-butyl)-6-{[(1-methyl-2-imidazolyl)methyl][(6- methyl-2-pyridyl)methyl]aminomethyl}phenol(HtbuL(im)(Mepy)), were prepared. They were structurally characterized by the X-ray crystallographic method to have a square-pyramidal structure with a weakly coordinating group at an apical position. The phenol moiety of [CuCl(tbuL(Mepy))] (2), [CuCl(tbuL(Mepy)2)] (3), and [CuCl(tbuL(im)(Mepy))] (4) was revealed to be coordinated equatorially; it was converted to the phenoxyl radical upon oxidation with Ce(IV), giving a new absorption peak at 405-420 nm. ESR measurements at low temperatures and resonance Raman spectra established that the radical species has a Cu(II)-phenoxyl radical bond. The cyclic voltamnograms exhibited a quasi-reversible redox wave at E(1/2) = 0.56-0.61 V (vs. Ag/AgCl) corresponding to the formation of the phenoxyl radical, which displayed a first order decay with a half life of 65 and 62 min at -20 °C for 2 and 4, respectively, while that for 3 was only 9.0 min at -40°C. The radical stability increased with the donor ability of the equatorial N ligands.
- Shimazaki, Yuichi,Huth, Stefan,Hirota, Shun,Yamauchi, Osamu
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p. 1187 - 1195
(2007/10/03)
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