676365-39-2Relevant academic research and scientific papers
Functional models for enzyme-substrate adducts of catechol dioxygenase enzymes: The Lewis basicity of facially coordinating tridentate phenolate ligands tunes the rate of dioxygenation and product selectivity
Visvaganesan, Kusalendiran,Ramachitra, Somasundaram,Palaniandavar, Mallayan
, p. 87 - 94 (2012/02/03)
A few iron(III) 3,5-di-tert-butylcatecholate (DBC2-) adducts of the type [Fe(L)(DBC)(CH3OH)], where L is a tridentate substituted monophenolate ligand such as 2-((N-benzylpyrid-2-ylmethylamino)methyl)phenol (H(L1)), 2-((N-benzylpyrid-2-ylmethylamino)-methyl)-4,6-dimethylphenol (H(L2)), 2-((N-benzylpyrid-2-ylmethylamino)methyl)-4,6-di-tert-butylphenol (H(L3)) and 2-((N-benzylpyrid-2-ylmethylamino)methyl)-4-nitrophenol (H(L4)), have been isolated and characterized by elemental and ESI-MS analysis. The spectral and electrochemical properties and dioxygenase activities of the adducts have been studied in methanol solution. Upon varying the substituents on the phenolate ring from electron-releasing to electron-withdrawing, the redox potential of DBSQ/DBC2- couple is shifted to a more positive value indicating an increase in covalency of iron(III)-catecholate bonds. All the complexes elicit cleavage of DBC2- using molecular oxygen to afford both intra- (I) and extradiol (E) cleavage products with the product selectivity (E/I) varying in the range 0.3-1.9. Interestingly, the incorporation of electron-withdrawing substituents facilitates the regioselective extradiol cleavage of catechol while that of electron-releasing substituents facilitate the regioselective intradiol cleavage.
Zinc and enolato-magnesium complexes based on bi-, tri- and tetradentate aminophenolate ligands
Zheng, Zhanjiang,Zhao, Gang,Fablet, Remy,Bouyahyi, Miloud,Thomas, Christophe M.,Roisnel, Thierry,Casagrande Jr., Osvaldo,Carpentier, Jean-Francois
experimental part, p. 2279 - 2291 (2009/03/11)
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.
Half-sandwich η6-benzene Ru(II) complexes of phenolate-based pyridylalkylamine/alkylamine ligands: Synthesis, structure, and stabilization of one-electron oxidized species
Mishra, Haritosh,Mukherjee, Rabindranath
, p. 3248 - 3260 (2008/02/08)
Four half-sandwich ruthenium(II) complexes [(η6-C6H6)Ru(L1-O)][PF6] (1), [(η6-C6H6)Ru(L2-O)][PF6] (2), [(η6-C6H6)Ru(L3-O)][PF6] (3), [(η6-C6H6)Ru(L4-O)][PF6] (4a), and [(η6-C6H6)Ru(L4-O)][BPh4] (4b) [L1-OH, 4-nitro-6-{[(2′-(pyridin-2-yl)ethyl)methylamino]methyl}-phenol; L2-OH, 2,4-di-tert-butyl-6-{[(2′-(pyridin-2-yl)ethyl)methylamino]methyl}-phenol; L3-OH, 2,4-di-tert-butyl-6-{[2′-((pyridin-2-yl)benzylamino)methyl}-phenol; L4-OH, 2,4-di-tert-butyl-6-{[(2′-imethylaminoethyl)methylamino]methyl}-phenol (L4-OH)], supported by a systematically varied series of tridentate phenolate-based pyridylalkylamine and alkylamine ligands are reported. The molecular structures of 1-3, 4a, and 4b have been elucidated in solution using 1H NMR spectroscopy and of 1, 3, and 4b in the solid state by X-ray crystallography. Notably, due to coordination by the ligands the Ru center assumes a chiral center and in turn the central amine nitrogen also becomes chiral. The 1H NMR spectra exhibit only one set of signals, suggesting that the reaction is completely diastereoselective [1: SRu,SN/RRu,RN; 2: RRu,RN/SRu,SN; 3: SRu,RN/RRu,SN; 4b: SRu,RN/RRu,SN]. The crystal packing in 1 and 3 is stabilized by C-H...O interactions, in 4b no meaningful secondary interactions are observed. From the standpoint of generating phenoxyl radical, as investigated by cyclic voltammetry (CV), complex 1 is redox-inactive in MeCN solution. However, 2, 3, and 4a generate a one-electron oxidized phenoxyl radical coordinated species [2]2+{radical dot}, [3]2+{radical dot}, and [4a]2+{radical dot}, respectively. The radical species are characterized by CV, UV-Vis, and EPR spectroscopy. The stability of the radical species has been determined by measuring the decay constant (UV-Vis spectroscopy).
How Single and Bifurcated Hydrogen Bonds Influence Proton-Migration Rate Constants, Redox, and Electronic Properties of Phenoxyl Radicals
Thomas, Fabrice,Jarjayes, Olivier,Jamet, Helene,Hamman, Sylvain,Saint-Aman, Eric,Duboc, Carole,Pierre, Jean-Louis
, p. 594 - 597 (2007/10/03)
Hydrogen-bonded phenoxyl radicals are made and the strength of the hydrogen bond between the O(phenoxyl) and the H(ammonium) atoms strongly affects their stability. The rate constants for the intramolecular proton-migration process in these systems are reported and a bifurcated hydrogen-bonded system has been characterized (see model). Investigations show that the proton transfer from the phenoxyl-radical cation to the tertiary amine is assisted by a neighboring nitrogen atom.
