Ewa Kita

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Oxidation in vitro of chromium(III) dietary supplements mer-[Cr(pic)₃] and trans(S,S)-[Cr(Cys)₂]⁻ by hydrogen peroxide

Emilia Nieczyporowska, Ewa Kita, Anna Katafias, Anna Bajek, more

Transition Metal Chemistry > 2017 > 42 > 7 > 623-633

Biological tests performed using 3T3 fibroblasts indicated low cytotoxicities for the complexes mer-[Cr(pic)₃] and trans(S,S)-[Cr(Cys)₂]⁻, where pic = picolinate anion and Cys = cysteine. Oxidation of these complexes by hydrogen peroxide was studied in NaOH and NaHCO₃ media. Electronic (UV–Vis) and EPR spectroscopies were used to monitor the reaction course. Hydrogen peroxide oxidizes chromium(III)...

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Hydrolytic and redox transformations of chromium(III) bis-oxalato complexes with glutaminic acid and glutamine: a kinetic, UV–Vis and EPR, study

Emilia Kiersikowska, Ewa Kita, Przemysław Kita, Grzegorz Wrzeszcz

Transition Metal Chemistry > 2016 > 41 > 4 > 435-445

The title complexes have been synthesized, chromatographically isolated and characterized by their ligands to metal ratio determinations and spectroscopic analyses. The kinetics of the first aquation stage, i.e., the amino acid chelate ring opening via the Cr–N bond cleavage, has been studied spectrophotometrically in acidic and alkaline media. Hydrogen peroxide oxidizes the complexes in alkaline...

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Hydrolytic chromium(III)–sulfur bond cleavage in chromium(III)–cysteine complexes

Emilia Kiersikowska, Ewa Kita, Przemysław Kita

Transition Metal Chemistry > 2015 > 40 > 4 > 427-435

Two chromium(III)–cysteine complexes, [Cr(Cys) ₂ ] ⁻ and [Cr(Cys)(H ₂ O) ₃ ] ⁺ , have been synthesized, and their reactivity in aqueous solution studied. Kinetics of the acid-catalyzed Cr–S bond fission was studied in strongly acidic medium, monitoring the absorbance decrease of the S → Cr CT band. The dependences of the pseudo-first-order...

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Kinetic studies on H⁺- and OH⁻-catalysed aquation of bis-aspartatochromium(III)

Ewa Kita, Emilia Kiersikowska, Hasan Marai, Karolina Mierkiewicz

Transition Metal Chemistry > 2014 > 39 > 1 > 63-70

A potential synthetic biochromium source, bis-aspartatochromium(III) ion (where Asp is a tridentate N,O,O′-ligand, bonded via amine nitrogen and carboxylate oxygen atoms) has been obtained and characterized in aqueous solution. Kinetics of partial dechelation of the complex catalysed by H⁺ and OH⁻ ions has been studied spectrophotometrically within 0.1–1.0 M HClO₄ and 0.1–1.0 M NaOH ranges under first-order...

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Kinetic studies on acid- and base-catalyzed aquation of bis-alaninatochromium(III) and on oxidation of tris- and bis-Aa–chromium(III) complexes (Aa = Gly, Ala, Asn) by H₂O₂

Emilia Kiersikowska, Hasan Marai, Magdalena Mątewska, Grzegorz Wrzeszcz, more

Transition Metal Chemistry > 2014 > 39 > 4 > 361-371

Two aqua derivatives of [Cr(Ala)₃] were characterized in solution. Acid-catalyzed aquation of cis-[Cr(Ala)₂(H₂O)₂]⁺ leads to inert [Cr(Ala)(H₂O)₄]²⁺, whereas base hydrolysis of cis-Cr(Ala)₂(OH)₂]⁻ causes dissociation of both the Ala ligands and formation of chromates(III). Kinetics of these processes have been studied spectrophotometrically in both 0.1–1.0 M HClO₄ and 0.2–0.9 M NaOH under first-order...

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Kinetic studies on H⁺-catalyzed aquation and hydrogen peroxide oxidation of tris-asparaginatochromium(III)

Emilia Kiersikowska, Hasan Marai, Grzegorz Wrzeszcz, Ewa Kita

Transition Metal Chemistry > 2013 > 38 > 6 > 603-610

Tris-asparaginatochromium(III), [Cr(Asn)₃]⁰ (where Asn forms a 5-membered chelate ring via amine nitrogen and α-carboxylate oxygen atoms) and its mono- and diaqua-derivatives were obtained, and their acid-catalyzed aquation was studied. The first reaction for [Cr(Asn)₃]⁰ and [Cr(Asn)₂(H₂O)₂]⁺ is the chelate ring opening at the Cr-NH₂ bond, leading to metastable intermediates. Kinetics of these processes...

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Effect of co-ligands on photoredox pathways in Cr(III) oxalate complexes

Joanna Wiśniewska, Hasan Marai, Andrzej Karocki, Grzegorz Stopa, more

Journal of Photochemistry & Photobiology, A: Chemistry > 2012 > 250 > Complete > 78-84

The photochemical behaviour of some mixed ligand chromium(III) complexes with amino acids, [Cr(C ₂ O ₄ ) ₂ (Aa)] ⁿ⁻ (where Aa=alanine, valine, serine, cysteine, asparagine, aspartic acid) was studied. The attention was focused on the photoredox mode, which proceeded via inner- or intramolecular pathway yielding Cr(II) species and hydrated electrons, respectively. The...

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Kinetic studies on H⁺-catalysed aquation of some chromium(III)-oxalato-amino acid complexes

Hasan Marai, Ewa Kita, Joanna Wojciechowska, Paula Wróbel

Transition Metal Chemistry > 2012 > 37 > 2 > 215-223

The following chromium(III) complexes with serine (Ser) and aspartic acid (Asp) were obtained and characterized in solution: [Cr(ox)₂(Aa)]²⁻ (where Aa = Ser or Asp), [Cr(AspH₋₁)₂]⁻ and [Cr(ox)(Ser)₂]⁻. In acidic solutions, [Cr(ox)₂(Aa)]²⁻ undergoes acid-catalysed aquation to cis-[Cr(ox)₂(H₂O)₂]⁻ and the appropriate amino acid. [Cr(ox)(Ser)₂]⁻ undergoes consecutive acid-catalysed Ser liberation to...

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Kinetics and mechanism of base hydrolysis of mer-[Cr(pic)₃]⁰ and [Cr(ox)₂(pic)]²⁻ (pic = picolinate, ox = oxalate)

Hasan Marai, Ewa Kita, Joanna Wiśniewska

Transition Metal Chemistry > 2012 > 37 > 1 > 55-62

Mer-[Cr(pic)₃]⁰ and [Cr(ox)₂(pic)]²⁻ undergo successive base hydrolysis to give chromates(III). Dissociation of the first ligand, pic from [Cr(pic)₃]⁰ and ox from [Cr(ox)₂(pic)]²⁻, proceeds in two stages, namely initial chelate-ring opening followed by slower liberation of the monodentate ligand. Kinetics of both the stages were studied spectrophotometrically in 0.2–0.9 M NaOH solution, under pseudo-first-order...

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Kinetic studies on H⁺-catalysed aquation of chromium(III)-oxalato-asparaginato and chromium(III)-oxalato-histidinato complexes

Hasan Marai, Ewa Kita, Emilia Kiersikowska, Sylwia Kuchta, more

Transition Metal Chemistry > 2012 > 37 > 4 > 337-344

Three chromium(III) complexes with asparagine (Asn) and histidine (His) of the [Cr(ox)₂(Aa)]²⁻ type, where Aa = N,O–Asn, N,O–His or N,N′–His, were obtained and characterized in solution. The complexes with N,O–Aa undergo acid-catalysed aquation to give a free amino acid and cis-[Cr(ox)₂(H₂O)₂]⁻, whereas the complex with N,N′–His undergoes parallel reaction paths: (1) isomerization to the N,O–His complex...

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Kinetic studies on pH controlled partial dechelation of the trans-imidazole-[Cr(His)₂]⁺ cation

Hasan Marai, Ewa Kita, Sylwia Kuchta

Transition Metal Chemistry > 2012 > 37 > 8 > 735-742

Partial dechelation of one tridentate N,N′,O-histidine in trans-imidazole-[Cr(His)₂]⁺ (where N and N′ are amine and imidazole nitrogen atoms, respectively, and O is carboxylate oxygen) has been studied. The aquation process is both acid and base catalyzed and the product with didentate His is converted back into the substrate at pH 4–7. Kinetics of the chelate ring opening were studied spectrophotometrically...

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Kinetic studies on chromium-glycinato complexes in acidic and alkaline media

Ewa Kita, Hasan Marai, Tadeusz Muzioł, Karolina Lenart

Transition Metal Chemistry > 2011 > 36 > 1 > 35-44

Two solid complexes, fac–[Cr(gly)₃] and [Cr(gly)₂(OH)]₂, (where gly is glycinato ligand) were prepared and their acid-catalysed aquation products were identified. The structure of [Cr(gly)₃] was solved by X-ray diffraction, revealing a cationic 3D sublattice with perchlorate anions inside its cavities. Acid-catalysed aquation of [Cr(gly)₃] and [Cr(gly)₂(OH)]₂ leads to the same inert product, [Cr(gly)...

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Kinetic studies on acid-catalysed aquation of some [Cr(ox)₂(amino acid)]²⁻ complexes

Ewa Kita, Rafał Lisiak

Transition Metal Chemistry > 2011 > 36 > 8 > 855-860

Three chromium(III) complexes of general formula [Cr(ox)₂(Aa)]²⁻ (Aa is an α-amino acid, namely alanine, valine or cysteine) were obtained and characterized in solution. In acidic solutions, [Cr(ox)₂(Aa)]²⁻ undergo acid-catalysed aquation to cis-[Cr(ox)₂(H₂O)₂]⁻ and the appropriate amino acid. The process goes through a metastable intermediate with monodentate amino acid coordinated via the carboxylate...

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Photoredox reactions of Cr(III) mixed-ligand complexes

Joanna Wiśniewska, Hasan Marai, Andrzej Karocki, Konrad Szaciłowski, more

Journal of Photochemistry & Photobiology, A: Chemistry > 2010 > 209 > 2-3 > 121-127

Irradiation of chromium(III) complexes with oxalate and pyridinedicarboxylate ligands (pda=2,3-, 2,4-, or 2,5-dicarboxylate) leads to diverse behaviors, dictated by light energy, presence of oxygen and the ligand nature. Irradiation within the MC bands is unaffected by O ₂ and results in ligand substitution. The LMCT excitation is effective only when oxalate is coordinated to Cr(III); then...

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Potential biochromium sources; kinetic studies on acid- and base-catalyzed aquation of [Cr(ox)₂(2-(aminomethyl)pyridine]⁻

Ewa Kita, Rafał Lisiak

Transition Metal Chemistry > 2010 > 35 > 4 > 441-450

Acid- and base-catalyzed hydrolysis of [Cr(ampy)(ox)₂]⁻, where ampy = 2-(aminomethyl)pyridine, leads to successive dissociation of the ligands via concurrent reaction paths, whereas at pH 1–9 only ampy is liberated as a result of spontaneous processes. The first ligand dissociation proceeds via aqua intermediates with one-end bonded ampy (1) or ox ligands (2), respectively, which in alkaline media...

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Mixed-ligand chromium(III)-oxalate-pirydinedicarboxylate complexes: potential biochromium sources: kinetic studies in NaOH solutions and effect on 3T3 fibroblasts proliferation

Ewa Kita, Hasan Marai, Lisiak Michał, Miłosz Jasiński, more

Transition Metal Chemistry > 2010 > 35 > 2 > 177-184

Base hydrolysis of [Cr(ox)₂(pda)]³⁻ (where pda is N,O-bonded 2,4- and 2,5- pyridinedicarboxylic acid dianion) causes successive ligand dissociation and leads to formation of a mixture of oligomeric chromium(III) species, known as chromates(III). The main reaction path proceeds through [Cr(ox)(pda)(OH)₂]³⁻ and [Cr(pda)(OH)₄]³⁻ complexes. The kinetics of the first oxalate dissociation was studied spectrophotometrically,...

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Kinetics and mechanism of base hydrolysis of chromium(III) complexes with oxalates and quinolinic acid

Ewa Kita, Hasan Marai

Transition Metal Chemistry > 2009 > 34 > 6 > 585-591

Base hydrolysis of [Cr(ox)₂(quin)]³⁻ (where quin²⁻ is N,O-bonded 2,3-pyridinedicarboxylic acid dianion) causes successive ligand dissociation and leads to a formation of a mixture of oligomeric chromium(III) species, known as chromates(III). The reaction proceeds through [Cr(ox)(quin)(OH)₂]³⁻ and [Cr(quin)(OH)₄]³⁻ formation. Dissociation of oxalato ligands is preceded by the opening of the Cr-quin...

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Chromium(III) complexes with lutidinic acid: kinetic studies in HClO₄ and NaOH solutions

Ewa Kita, Hasan Marai, Łukasz Iglewski

Transition Metal Chemistry > 2009 > 34 > 1 > 75-84

Chromium(III)-lutidinato complexes of general formula [Cr(lutH)_n(H₂O)_6−2n]³⁻ⁿ (where lutH⁻ is N,O-bonded lutidinic acid anion) were obtained and characterized in solution. Acid-catalysed aquation of [Cr(lutH)₃]⁰ leads to only one ligand dissociation, whereas base hydrolysis produces chromates(III) as a result of subsequent ligand liberation steps. The kinetics of...

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Mixed chromium(III) complexes with pyridinedicarboxylato and oxalato ligands: kinetic studies in HClO₄ solutions

Ewa Kita, Hasan Marai, Kornelia Jach, Anna Orłowska

Transition Metal Chemistry > 2009 > 34 > 2 > 217-224

Three chromium(III) complexes of general formula [Cr(ox)₂(pdaH)]²⁻ (where ox = C₂O₄ ²⁻ and pdaH⁻ is N,O-bonded 2,3-, 2,4- or 2,5-pyridinedicarboxylic acid anion) were obtained and characterized in solution. Acid-catalysed aquation of [Cr(ox)₂(pdaH)]²⁻ gave two products: [Cr(ox)(pdaH)(H₂O)₂]⁰ (P₁) and cis-[Cr(ox)₂(H₂O)₂]²⁻ (P₂). The kinetics of these reactions were studied spectrophotometrically, within...

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Synthesis and kinetic studies in aqueous solution on chromium(III) complexes with isocinchomeronic acid—potential new biochromium sources

Ewa Kita, Hasan Marai, Karolina Zając

Transition Metal Chemistry > 2008 > 33 > 2 > 211-217

The chromium(III) complexes with a new potential chromium transporting ligand—2,5-pyridinedicarboxylic acid (isocinchomeronic acid, icaH₂):[Cr(icaH)₃]⁰, [Cr(icaH)₂ (H₂O)₂]⁺ and [Cr(icaH)(H₂O)₄]²⁺ (where icaH = N,O-bonded isocinchomeronic acid anion), have been obtained and characterized in solution. The [Cr(icaH)₃]⁰ complex undergoes aquation in acidic media to the diaqua-product. Kinetics of this...

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Search results for: Ewa Kita

Oxidation in vitro of chromium(III) dietary supplements mer-[Cr(pic)₃] and trans(S,S)-[Cr(Cys)₂]⁻ by hydrogen peroxide

Hydrolytic and redox transformations of chromium(III) bis-oxalato complexes with glutaminic acid and glutamine: a kinetic, UV–Vis and EPR, study

Hydrolytic chromium(III)–sulfur bond cleavage in chromium(III)–cysteine complexes

Kinetic studies on H⁺- and OH⁻-catalysed aquation of bis-aspartatochromium(III)

Kinetic studies on acid- and base-catalyzed aquation of bis-alaninatochromium(III) and on oxidation of tris- and bis-Aa–chromium(III) complexes (Aa = Gly, Ala, Asn) by H₂O₂

Kinetic studies on H⁺-catalyzed aquation and hydrogen peroxide oxidation of tris-asparaginatochromium(III)

Effect of co-ligands on photoredox pathways in Cr(III) oxalate complexes

Kinetic studies on H⁺-catalysed aquation of some chromium(III)-oxalato-amino acid complexes

Kinetics and mechanism of base hydrolysis of mer-[Cr(pic)₃]⁰ and [Cr(ox)₂(pic)]²⁻ (pic = picolinate, ox = oxalate)

Kinetic studies on H⁺-catalysed aquation of chromium(III)-oxalato-asparaginato and chromium(III)-oxalato-histidinato complexes

Kinetic studies on pH controlled partial dechelation of the trans-imidazole-[Cr(His)₂]⁺ cation

Kinetic studies on chromium-glycinato complexes in acidic and alkaline media

Kinetic studies on acid-catalysed aquation of some [Cr(ox)₂(amino acid)]²⁻ complexes

Photoredox reactions of Cr(III) mixed-ligand complexes

Potential biochromium sources; kinetic studies on acid- and base-catalyzed aquation of [Cr(ox)₂(2-(aminomethyl)pyridine]⁻

Mixed-ligand chromium(III)-oxalate-pirydinedicarboxylate complexes: potential biochromium sources: kinetic studies in NaOH solutions and effect on 3T3 fibroblasts proliferation

Kinetics and mechanism of base hydrolysis of chromium(III) complexes with oxalates and quinolinic acid

Chromium(III) complexes with lutidinic acid: kinetic studies in HClO₄ and NaOH solutions

Mixed chromium(III) complexes with pyridinedicarboxylato and oxalato ligands: kinetic studies in HClO₄ solutions

Synthesis and kinetic studies in aqueous solution on chromium(III) complexes with isocinchomeronic acid—potential new biochromium sources

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