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Determination of formation constants of uranyl(VI) complexes with a hydrophilic SO3-Ph-BTP ligand, using liquid-liquid extraction

Steczek L., Narbutt J., Charbonnel M. -C., Moisy P.

Nukleonika

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2015

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Vol. 60, No. 4, part 2

821--827

EN

Complex formation between uranyl ion, UO2 2+, and a hydrophilic anionic form of SO3-Ph-BTP4– ligand, L4–, in water was studied by liquid-liquid extraction experiments performed over a range of the ligand and HNO3 concentrations in the aqueous phase, at a constant concentration of nitrate anions at 25°C . The competition for UO2 2+ ions between the lipophilic TODGA extractant and the hydrophilic L4– ligand leads to the decrease in the uranyl distribution ratios, D, with an increasing L4– concentration. The model of the solvent extraction process used accounts – apart from uranyl complexation by TODGA and SO3-Ph-BTP4– – also for uranyl complexation by nitrates and for the decrease in the concentration of the free L4– ligand in the aqueous phase, due to its protonation, bonding in the uranyl complex and the distribution between the two liquid phases. The unusually strong dependence of the D values on the acidity, found in the experiment, could hardly be explained as due to L4– protonation merely. Three hypotheses were experimentally tested, striving to interpret the data in terms of additional extraction to the organic phase of ion associates of protonated TODGA cation with either partly protonated anionic L4– ligands or anionic UO2 2+ complexes with NO3 – or L4–. None of them has been confi rmed. The analysis of the results, based on the formal correction of free ligand concentrations, points to the formation of 1 : 1 and 1 : 2 uranyl – SO3-Ph-BTP complexes in the aqueous phase. The conditional formation constant of the 1:1 complex has been determined, logβL,1 = 2.95 ± 0.15.

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Coordination States and Apparent Molar Volumes of Cobalt(II) Perchlorate and Cobalt(II) Chloride in N, N'-Diethylacetamide Solutions at 25 graduate C

Lipski P., Pastewski R., Grzybkowski W.

Polish Journal of Chemistry

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2005

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Vol. 79 / nr 9

1445-1459

EN

Visible absorption spectra and apparent molar volumes for CoCl2 and Co(ClO4)2 in N,N-diethylacetamide (DEA) as well as the spectra for the Co(ClO4)2 - CoCl2 - DEAand CoCl2- LiCl - DEA systems were studied. The results indicate formation of the electrically neutral CoCl2(DEA)2 complex, being the predominating chloro-complex of cobalt(II) in the solutions of CoCl2 in DEA. The formation constants of the consecutive chloro-complexes of cobalt(II) have been determined: logK1 = 5.28(+-0.10), logK2 =+ - 6.10(_0.08), logK3 = 3.31(+ - 0.05) and logK4 = 0.74(+ - 0.05).

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Potentiometric and spectrophotometric determination of the stability constants of luteolin (3',4',5,7-tetrahydroxyflavone) complexes with aluminium(III) and iron(III)

Karadag R.

Chemia Analityczna

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2003

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Vol. 48, No. 6

931-937

EN

In this study, one determined stability constants of the complexes of luteolin with aluminium (III) and iron(lll). Potentiometric methods of Calvin-Bjerrum and Irving-Rossotti, and spec-trophotometric assay have been utilised. The evaluated protonation constants of the ligand were: logk(1) = 8.95, logk(2) = 8.10, and logk(3) = 6.85 at the 25°C. For the aluminium and iron complexes the subsequent logarithms of formation constants were found: for Al 17.50, 15.00, 4.75 and for iron: 19.60, 19.40, 17.82.

PL

Spektrofotometrycznie i potencjometrycznie stosując metody Calvina-Bjerruma i Irvinga-Rossottiego, wyznaczono stale wartości kompleksów luteoliny z glinem(III) i żelazem(III). Wyznaczone stałe protonowania ligandu wynosiły log k(2) = 8,95; log k2 = 8,10; log k(3) = 6,85 w temperaturze 25°C. Dla kompleksów glinu kolejne wartości logarytmów stałych tworzenia wynosiły: 17,50; 15,00; 4,75, zaś dla kompleksów żelaza: 19,60; 19,40; 17,82.