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Detection of Nitrate(NO-2) Ions Produced in Disproportionation of Nitrogen(II) Oxide in Aqueous Solution

Kufelnicki A., Jaciubek-Rosińska J.

Ecological Chemistry and Engineering. S

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2012

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Vol. 19, nr 1

39-46

EN

The nitrate ions (NO ) 2 - , products of disproportionation of NO in aqueous solution, were detected by an Orion Nitrite Electrode 97-46. Calibrations by means of standard NaNO2 solutions within the range 0.001÷100 ppm indicated linear dependence of EMF on ppm within 1÷100 ppm. Measurements justified the usefulness of this detection method of NO in solutions of OH- concentration lower than 10–2 mol dm–3 since at higher concentrations the EMF values exceeded the measurement range of the electrode. Occurrence of nitrate ions produced in the disproportionation reaction was additionally confirmed in dependence of OH- concentration by near UV and fluorescence spectra. The calibrated ion-selective nitrate electrode has also been shown, on the basis of Co(II)-dipeptide-OH– systems, as a useful tool in studying reversible NO uptake by Co(II) chelates in aqueous solution. Such a reaction may be regarded as simulating the harmful binding of NO by hemoglobin, where it substitutes the isoelectronic dioxygen.

PL

Jony azotanowe (NO ) 2- , produkty dysproporcjonowania NO w roztworze wodnym, oznaczano za pomocą jonoselektywnej elektrody Orion Nitride Electrode 97-46. Kalibracje za pomocą standardowych roztworów NaNO2 w zakresie 0.001÷100 ppm wskazywały liniową zależność SEM od ppm w zakresie 1÷100 ppm. Pomiary uzasadniły użyteczność tej metody wykrywania NO w roztworach o stężeniu OH– mniejszym niż 10–2 mol dm–3, ponieważ przy większych stężeniach wartości SEM przekraczały zakres pomiarowy elektrody. Występowanie jonów azotanowych tworzonych w reakcji dysproporcjonowania było dodatkowo potwierdzane, w zależności od stężenia OH–, za pomocą widm w bliskim UV i widm fluorescencyjnych. Wykazano także, na przykładzie układów Co(II)-dipeptyd-OH–, że kalibrowana jonoselektywna elektroda na jony azotanowe (NO ) 2- może być użytecznym narzędziem w badaniu odwracalnego wiązania NO przez chelaty Co(II) w roztworze wodnym, reakcji symulującej szkodliwe działanie tlenku azotu(II) na hemoglobinę.

2

Uptake of Molecular Oxygen by Co(II) Chelates with Peptides in Aqueous Solution. Part XII. Non-covalent Interactions in the Cobalt(II) - Diastereoisomeric Phenylalanyl Dipeptide Systems. Effect on Kinetics of Oxygenation

Kufelnicki A., Świątek A.

Polish Journal of Chemistry

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2008

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Vol. 82, nr 5

981-991

EN

The interactions of Co(II) with a group of diastereoisomeric dipeptides containing a side chain with the aromatic phenyl ring have been studied in aqueous solution, both under inert atmosphere and in the presence of dioxygen. An effect of stereoselectivity has been observed in the metal promoted deprotonations, examined by glass electrode potentiometry and correlated with the results of UV/Vis spectroscopy. The kinetics of oxygenation were studied by the stopped flow method and related to the potentiometric results.

3

Kinetic Studies of Nitric Oxide Uptake in Co(II)-Dipeptide-NO-OH- Systems by the Stopped-Flow Method

Kufelnicki A., Jaciubek-Rosińska J.

Polish Journal of Chemistry

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2006

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Vol. 80, nr 5

783-790

EN

The known up to now reactions of NO uptake by cobalt(II) chelates with selected dipeptides, observed previously by classic volumetric and pH-metric measurements, were now investigated kinetically by using the rapid kinetics stopped-flow method. The kinetic results could have been correlated with the reversibility of nitrosylation (estimated spectrophotometrically in the near IR after re-argonation).

4

Equilibria in Cobalt(II) - Amino Acid - Imidazole System under Oxygen-free Conditions. Part I. Studies on Mixed Ligand Systems with L-alfa-Alanine

Woźniczka M., Pająk M., Vogt A., Kufelnicki A.

Polish Journal of Chemistry

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2006

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Vol. 80, nr 12

1959-1966

EN

Glass electrode potentiometry and UV/Vis spectrophotometry experiments have been carried out in order to determine the equilibria in an oxygen-free Co(II)-Amac-Himid system in aqueous solution, where Amac = L-alfa-alanine and Himid = 1,3-diazole (imidazole). The presence of axial imidazole in the structure of the ternary complex was implicated by using a [Co(imid)2]n polymer as starting material. Two proposed coordination modes of the mixed-ligand complex have been confirmed both by suitable experimental methods and by a fitting procedure (using EMF and absorbance data). One of these coordination modes is known as a model imitating the metal center in hemoglobin, whereas the other one has not been considered as yet.

5

Complexes of Uracil (2,4-Dihydroxypyrimidine) Derivatives. Part II. Potentiometric and Luminescence Studies with Eu(III)

Kufelnicki A., Kupińska I., Lis S., Hnatejko Z.

Polish Journal of Chemistry

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2003

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Vol. 77 / nr 8

1019-1025

EN

Luminescence spectroscopy studies were carried out on europium(III) complexation with HL = uracil, thymine (5-methyluracil), 6-chloromethyluracil, 5-hydroxymethyluracil and 6-methyluracil in acidic perchlorate solutions. In acidic medium the decrease of the hydration number with increasing the ligand excess indicates a consecutive complexation via metal - O4 coordination. The potentiometric method confirmed the possibility of coordination by N3 at higher pH for thymine, 6-chloromethyluracil and 6-methyluracil. The formation of hydroxo species has been ascertained for all the ligands.

6

Complexes of uracil (2,4-Dihydroxypyrimidine) Derivatives. Part I. Cu(II), Ca(II) and MG(II) Coordination with Uracil and Related Compounds in Aqueous Solution

Kufelnicki A., Kupińska I., Jezierska J., Ochocki J.

Polish Journal of Chemistry

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2002

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Vol. 76 / nr 11

1559-1570

EN

Potentiometric pH studies were carried out on proton and metal (Cu(II), Ca(II) and Mg(II)) complexes of HL = uracil, thymine (5-methyluracil), 6-chloromethyluracil, 5-hydroxymethyluracil, 6-methyluracil and a diethyl 6-uracilmethylphosphonate derivative. For Cu(II) additional spectroscopic (absorption and EPR) measurements were carried out. The results have been compared with the literature data accessible only for uracil and thymine. A deprotonation of the ML complexes in a more basic solution was indicated, thus, extending the coordination mode proposed up to now for uracil and thymine. An electron withdrawing effect of substituents has been found for 6-chloromethyluracil and diethyl 6-uracilmethylphosphonate.

7

Reversible Uptake of Nitric Oxide in Co(II)-Dipeptide-NO-OH- Systems

Kufelnicki A., Jaciubek J.

Polish Journal of Chemistry

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2001

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Vol. 75, nr 12

1905-1911

EN

Uptake of nitric oxide by cobalt(II) chelates with selected dipeptides was iiwestigated by volumetric and spectrophotometric methods (UV, VIS). The temperaturę was reduced to ~0°C in order to inhibit the autooxidation of Co(II) to Co(III). The stoichiometry of NO addition and the reversibility of the reaction (by re-acidification and re-argonation) were investigated as well. The reaction was reversible in a varying degree depending on the kind of amino acid side groups used. The kinetic stability of the formed NO adducts was followed spectrophotometrically. Present and previous results, concerning fixation of dioxygen in similar systems, arę compared.

8

Uptake of molecular oxygen by Co(II) chelates with peptides in an aqueous colution : Part XI : Stereoselective properties of oxygenated diastereoisomeric dipeptide systems

Kufelnicki A., Świątek M.

Polish Journal of Chemistry

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1999

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vol. 73 nr 4

579-591

EN

The reaction of oxygen uptake by Co(II) complexes with a group of diastereoisimetric dipeptides, consisting of alanine and leucine in various chiral forms, has been studied in an aqueous solution. The structure of the bridging moiety has been discussed on the basis of spectroscopic results (UV, Vis, near IR, CD, ESR). The effect of stereoselectivity has been confirmed by studies of reversibility of oxygenation. Comparative ESR measurements were done for mixed complexes with imidazole as N-base in the axial position. All of the results were compared with that for glycine dipeptides (containing only one asymmetric atom).

9

Uptake of molecular oxygen by Co(II) chelates with peptides in aqueous solution. Part X. Diastereoisomeric dipeptides as auxiliary ligands in oxygen-free complexes

Kufelnicki A., Świątek M.

Polish Journal of Chemistry

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1998

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Vol. 72, nr 8

1897-1906

EN

Co(II) complexes with group of diastereoisomeric dipeptides consisting of alanine and leucine in various chiral forms have been studied in aqueous solution. The equilibria were determined by potentiometric and spectrophometric methods, using least-squares fotting procedures. The results were compared with those for glycine dipeptides containing only one asymmetric atom.