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Anionic O (anionic + o)

Distribution by Scientific Domains
Chemistry100%

Selected Abstracts

Anionic O,,- and ,-Vinyl Carbamoyl Translocation of 2-(O-Carbamoyl) Stilbenes.

CHEMINFORM, Issue 44 2004
Mark A. Reed
Abstract For Abstract see ChemInform Abstract in Full Text. [source]

"Inhibition" of the Enzyme Model TpPh,MeZn,OH by Diketo Compounds

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 24 2006
Teame Tekeste
Abstract In order to gain a structural understanding of zinc enzyme inhibition, the model complex TpPh,MeZn,OH was treated with various diketo compounds. ,-Keto carboxylic acids were attached to the zinc ion as anionic O,O-chelate ligands, of which benzoylformate was oxidatively decarboxylated in air to form the benzoate complex. Two functionalized ,-diketones did not use their functionality in forming the ,-diketonate complexes. Of the ,-diketones, 2,3-pentanedione formed the ,-keto enolate complex, while 1-phenyl-1,2-propanedione underwent oxidative C,C coupling resulting in a red dinuclear bis(,-keto enolato) complex. Of the diaryl-,-diketones, benzil did not react, but pyridil underwent hydrolytic cleavage to pyridine-2-carbaldehyde and picolinate, of which the latter was bound to the zinc ion as an N,O-chelate ligand.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

Enol Forms of 1,3-Indanedione, Their Stabilization by Strong Hydrogen Bonding, and Zwitterion-Assisted Interconversion

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 14 2010
Mark Sigalov
Abstract By analyzing NMR spectroscopic data, and supported by IR, UV/Vis, Raman, dielectrometry, and DFT techniques, a comprehensive study of the 1:2 adducts of picolinaldehyde and 1,3-indanediones is presented. The parent indanedione derivative 5 exists in an equilibrium between all-keto and enol forms, the latter being stabilized by an intramolecularO,H···N hydrogen bond. Only the all-keto form was observed in the 5,6-dimethoxy compound 6, whereas solely the enol tautomer was observed with its 5,6-dichloro analogue 7. Polar solvents and low temperatures shift the equilibrium towards the enol tautomer in 5. The structure of adduct 8, formed with isonicotinaldehyde, prevents the formation of intramolecular O,H···N hydrogen bonds and thus it exists in the all-keto form in low polar solvents. However, in DMSO solutions it adopts a zwitterionic form with a strong anionic O,···H···O hydrogen bond. Thus, the enol form in indanedione adducts was unequivocally characterized in solution and the factors that determine the keto,enol tautomerism, namely electronic effects, solvent, temperature, and intramolecular hydrogen bonds, have been methodically studied by spectroscopic and quantum mechanical methods. [source]

Osmium(II) and Ruthenium(II) Arene Maltolato Complexes: Rapid Hydrolysis and Nucleobase Binding

CHEMISTRY - A EUROPEAN JOURNAL, Issue 9 2007

Abstract Density functional calculations show that aquation of [Os(,6 -arene)(XY)Cl]n+ complexes is more facile for complexes in which XY=an anionic O,O-chelated ligand compared to a neutral N,N-chelated ligand, and the mechanism more dissociative in character. The O,O-chelated XY=maltolato (mal) [M(,6 - p -cym)(mal)Cl] complexes, in which p -cym=p -cymene, M=OsII (1) and RuII (2), were synthesised and the X-ray crystal structures of 1 and 2,2,H2O determined. Their hydrolysis rates were rapid (too fast to follow by NMR spectroscopy). The aqua adduct of the OsII complex 1 was 1.6,pKa units more acidic than that of the RuII complex 2. Dynamic NMR studies suggested that O,O-chelate ring opening occurs on a millisecond timescale in coordinating proton-donor solvents, and loss of chelated mal in aqueous solution led to the formation of the hydroxo-bridged dimers [(,6 - p -cym)M(,-OH)3M(,6 - p -cym)]+. The proportion of this dimer in solutions of the OsII complex 1 increased with dilution and it predominated at micromolar concentrations, even in the presence of 0.1,M NaCl (conditions close to those used for cytotoxicity testing). Although 9-ethylguanine (9-EtG) binds rapidly to OsII in 1 and more strongly (log,K=4.4) than to RuII in 2 (log,K=3.9), the OsII adduct [Os(,6 - p -cym)(mal)(9EtG)]+ was unstable with respect to formation of the hydroxo-bridged dimer at micromolar concentrations. Such insights into the aqueous solution chemistry of metal,arene complexes under biologically relevant conditions will aid the rational design of organometallic anticancer agents. [source]