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3 Polish Journal of Chemistry

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Speciation and Spectra of Bromokojatoiron(III) Complexes in Aqueous Solutions

Šima J., Šípoš R., Izakovic M., Valigura D., Tarapeík P.

Polish Journal of Chemistry

2006

Vol. 80, nr 12

1991-1999

The formation of iron(III) complexeswith chelating bromokojate anions L– was investigated in aqueous solutions as a function of the pH and c(Fe3+) : c(HL) molar ratio. Stability constants of the complexes [FeL(H2O)4]2+, [FeL(H2 O)3(OH)]+, [FeL2 (H2O)2]+, [FeL2(H2O)(OH)] and [FeL2(OH)2]– were determined by the evaluation of UV-VIS spectral data. Based on the stability constants, distribution of the above complexes, [Fe(H2O)6]3+, and [Fe(H2O)5(OH)]2+ in solutions of various composition were calculated. The paper indicates a compatibility of the used data treatment and that not taking hydroxo complexes into account. Properties of the investigated bromokojic acid and its iron(III) complexes are compared to those required for therapeutic application as alternative iron chelators.

Bell-shaped Dependence of the Quantum Yield of Fe(II) Formation in Irradiated Methanolic Solutions of Iron(III) Azido Methanolic Solutions of Iron(III) Azido Complexes with N, N'-Ethylenebis(benzoylacetoneiminato) Schiff Base Derivatives

Šima J., Horváthová L.

Polish Journal of Chemistry

2003

Vol. 77 / nr 12

1857-1865

The complexes trans-[Fe(4-R-benacen)(CH3OH)N3], where 4-R-benacen2- are tetradentate open-chain N2O2-Schiff base N,N'-ethylenebis(4-R-benzoylacetoneiminato) ligands (R =H, Cl, Br,OCH3, CH3) are redox stable in the dark. Under the impact of ultraviolet and/or visible radiation they undergo photochemical reactions, yielding Fe(II) and formaldehyde CH2O as final products. As an intermediate, _CH2OH radicals were identified by EPR spin trapping technique. The efficiency of the photoredox processes, expressed by the quantum yield of Fe(II) formation, Fi Fe(II) is strongly wavelength dependent and influenced by the peripheral groups R of the tetradentate ligands. It was found, that along with a frequently observed decrease in the quantum yield with decreasing the photon energy of incident radiation (Fi Fe(II) at 313 nm < Fi Fe(II) at 366 nm

Preparation and photoinduced processes of ferric complexes containing fluoride and tetradentate salen-type ligands

Sima J., Mrazova J., Kotocova A.

Polish Journal of Chemistry

1998

Vol. 72, nr 9

2079-2086

Tetradentate open-chain Schiff base ligands R-salen (R-salen are N,N'-ethylenebis(R-salicylideneiminato) dianions) and fluoride anions F(-) coordinate to the iron(III) central atom in methanol forming the complexes trans-[Fe(R-salen)(CH3OH)F]. The complexes are redox stable in the dark. Photoexcitation into their intraligand or ligand-to-metal charge transfer excited states leads to the photoreduction of Fe(III) to Fe(II), as a product of metanol oxidation the radical CH2OH was identified. The final products of the redox processes, Fe(II) and CH20, are formed in a 2:1 molar ratio. The efficiency of the photoredox processes is strongly wavelenght dependent and influenced by the peripheral groups R of the tetradentate ligands. A mechanism of deactivation processes is proposed and the influence of the peripheral groups R on the photoredox efficiency and electrochemical properties of the complexes is discussed.