Nicoletta Burger

Reactions of the aquapentacyanoferrate(II) ion with 2-nitroso-1-naphthol and 2-nitroso-1-naphthol-4-sulphonic acid

Abstract The aqua ligand of the aquapentacyanoferrate(II) ion was replaced by 2-nitroso-1-naphthol and its sulphonate derivative giving the analogous mononuclear nitroso-naphtholpentacyanoferrate(II) complex in the first stage of the reaction. In the second stage, a cyano-bridged binuclear product was obtained and characterized as pentacyanoferrate(II)-μ-cyano-tricyanonitrosonaphtholferrate(II). The latter reaction was catalysed by mercury(II) ions. The complexes were characterized on the basis of analytical, IR and UV-vis spectral data and have in the solid state and in solution a predominately quinone oximic structure. The preparation of the tris(2-nitroso-1-naphthol)ferrate(II) complex is also reported.

INHIBITION OF ACETYLCHOLINESTERASE BY THREE NEW PYRIDINIUM COMPOUNDS AND THEIR EFFECT ON PHOSPHONYLATION OF THE ENZYME

Three new mono-pyridinium compounds were prepared: 1-phenacyl-2-methylpyridinium chloride (1), 1-benzoylethylpyridinium chloride (2) and 1-benzoylethylpyridinium-4-aldoxime chloride (3) and assayed in vitro for their inhibitory effect on human blood acetylcholinesterase (EC 3.1.1.7, AChE). All the three compounds inhibited AChE reversibly; their binding affinity for the enzyme was compared with their protective effect (PI) on AChE phosphonylation by soman and VX. Compound 1 was found to bind to both the catalytic and the allosteric (substrate inhibition) sites of the enzyme with estimated dissociation constants of 6.9 microM (Kcat) and 27 microM (Kall), respectively. Compound 2 bound to the catalytic site with Kcat = 59 microM and compound 3 only to the allosteric site with Kall = 328 microM. PI was evaluated from phosphonylation measured in the absence and in presence of the compounds applied in a concentration corresponding to their Kcat or Kall value, and was also calculated from theoretical equations deduced from the reversible inhibition of the enzyme. Compounds 1 and 3 protected the enzyme from phosphonylation by soman and VX, whereas no protection was observed in the presence of compound 2 under the same conditions. Irrespective of the binding sites to AChE, PI for compounds 1 and 3 evaluated from phosphonylation agreed with PI calculated from reversible inhibition. Compound 3 was found to be a weak reactivator of methylphosphonylated AChE with Kr = 1.1 x 10(2) L mol-1 min-1.

Spectrophotometric studies of the reactions of pentacyanoferrate(II) complexes with three N-heterocyclic aldoximes

The colour reactions of three oximes with ammine- and nitrosyl-pentacyanoferrate(II) ions have been studied. The optimum reaction conditions, spectral characteristics and molar compositions have been found and some instability constants determined. The reactions can be used for the detection and determination of small amounts of the oximes examined.

The reactions of pentacyanoferrate(II) ions: Spectrophotometric study, detection and determination of N-heterocyclic aldoximes

The interactions of pyridine-4-aldoxime and pyridinium-4-aldoxime chloride with ammine- and nitrosyl-pentacyanoferrate(II) have been studied. The compounds react to form coloured water-soluble oximatopentacyanoferrate(II) complexes, which have been investigated spectrophotometrically. The reactions have been made the basis of spot-tests for these oximes and for their spectrophotometric determination.

A new cyano-bridged binuclear complex of pyridine-2-aldoxime with pentacyanoferrate(II) ions

Abstract A new cyano-bridged binuclear complex of the formula Na 5 [(CN) 5 Fe-NC-Fe(CN) 3 (pyCHNOH)]· 8H 2 O was prepared through the interaction of sodium amminepentacyanoferrate(II) and pyridine-2- aldoxime. The complex was characterized on the basis of analytical, infrared and electronic spectral data. Mercury(II) ions catalyse the formation of the complex which indicates that pyridine-2-aldoxime behaves as a bidentate ligand.

Reaction of 1-benzoylethylpyridinium-4-aldoxime chloride with aquapentacyanoferrate(II)

The results of a spectrophotometric investigation of the reaction of the biologically active salt 1-benzoylethylpyridinium-4-aldoxime chloride with aquapentacyanoferrate(II) ion are presented. In spite of the presence of two donor sites, only the carbonyl group of the ligand coordinates to the iron centre. Reaction kinetics are consistent with a dissociative mechanism.

Influence of mercury(II) and UV light on the reaction of pentacyanoferrate(II) ions with oximes

Abstract Mercury(II) ions catalyze the reaction of sodium aquopentacyanoferrate(II) with bidentate oximes and inhibit it with monodentate oximes. UV light increases the reaction rate of complex formation with all the examined oximes except pyridine-4-aldoxime.

Spectrophotometric studies, synthesis and properties of pentacyanoferrate(II) complexes with bis-quaternary pyridinium aldoximes

Abstract The colour reactions of three bis-pyridinium aldoximes with ammine- and nitrosyl-pentacyanoferrate(II) ions were studied. The optimum reaction conditions, the compositions and the stability constants of the produced complexes were determined. The compelxes were isolated and characterized by elemental analysis, visible, UV and IR spectral data. The examined compounds, although dioximes, are found to form 1 : 1 complexes.

Determination of iron and cyanide in cyanoferrate complexes.

A simple method of destroying cyano-complexes and of analysing for both iron and cyanide in a single sample of a cyanoferrate complex is proposed.

Spectrophotometric determination of ascorbic acid with potassium hexacyanoferrate(III)

A new, simple and rapid method of determination of ascorbic acid in amounts of 45-360 mug is described. The ascorbic acid is determined spectrophotometrically at 420 nm from the decrease in absorbance it causes in 1 x 10(-3)M hexacyanoferrate(III) in McIlvaine buffer at pH 5.2. The proposed method is suitable for the determination of ascorbic acid in pharmaceutical preparations and probably natural products.