Speciation of tin(II) in aqueous solution: thermodynamic and spectroscopic study of simple and mixed hydroxocarboxylate complexes

Cigala, Rosalia Maria; Crea, Francesco; Stefano, Concetta De; Milea, Demetrio; Sammartano, Silvio; Scopelliti, Michelangelo

doi:10.1007/s00706-013-0961-3

Cited by 27 publications

(16 citation statements)

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“…Sn 2+ has different acid-base properties and behaviors with respect to calcium and magnesium, since it tends to form polynuclear hydrolytic species also at low pH values [ 18 , 37 , 38 , 39 ]. Moreover, Sn 2+ forms, SnCl i (i = 1–3) species of significant stability and a mixed SnOHCl hydrolytic complex in chloride solutions.…”

Section: Resultsmentioning

confidence: 99%

The Solution Behavior of Dopamine in the Presence of Mono and Divalent Cations: A Thermodynamic Investigation in Different Experimental Conditions

et al. 2021

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The interactions of dopamine [2-(3,4-Dihydroxyphenyl)ethylamine, (Dop-)] with methylmercury(II) (CH3Hg+), magnesium(II), calcium(II), and tin(II) were studied in NaCl(aq) at different ionic strengths and temperatures. Different speciation models were obtained, mainly characterized by mononuclear species. Only for Sn2+ we observed the formation of binuclear complexes (M2L2 and M2LOH (charge omitted for simplicity); M = Sn2+, L = Dop−). For CH3Hg+, the speciation model reported the ternary MLCl (M = CH3Hg+) complex. The dependence on the ionic strength of complex formation constants was modeled by using both an extended Debye–Hückel equation that included the Van’t Hoff term for the calculation of enthalpy change values of the formation and the Specific Ion Interaction Theory (SIT). The results highlighted that, in general, the entropy is the driving force of the process. The sequestering ability of dopamine towards the investigated cations was evaluated using the calculation of pL0.5 parameter. The sequestering ability trend resulted to be: Sn2+ > CH3Hg+ > Ca2+ > Mg2+. For example, at I = 0.15 mol dm−3, T = 298.15 K and pH = 7.4, pL0.5 = 3.46, 2.63, 1.15, and 2.27 for Sn2+, CH3Hg+, Ca2+ and Mg2+ (pH = 9.5 for Mg2+), respectively. For the Ca2+/Dop- system, the precipitates collected at the end of the potentiometric titrations were analyzed by thermogravimetry (TGA). The thermogravimetric calculations highlighted the formation of solid with stoichiometry dependent on the different metal:ligand ratios and concentrations of the starting solutions.

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Section: Resultsmentioning

confidence: 99%

The Solution Behavior of Dopamine in the Presence of Mono and Divalent Cations: A Thermodynamic Investigation in Different Experimental Conditions

et al. 2021

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“…The equation has no theoretical foundation but is found to work reasonably well up to 0.1 mol dm −3 33 . Another widely applied approach in metal–ligand coordination studies determines conditional stability constants at a number of points within the ionic strength range of interest and uses adjustable parameters to fit the Debye-Hückel model 22 , 26 , 27 . This approach has been termed as direct method or extended Debye Hückel (EDH) model 3 , 22 , 34 .…”

Section: Introductionmentioning

confidence: 99%

Synergistic use of siderophores and weak organic ligands during zinc transport in the rhizosphere controlled by pH and ion strength gradients

Northover

Mao

Blasco

et al. 2022

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Citrate (Cit) and Deferoxamine B (DFOB) are two important organic ligands coexisting in soils with distinct different affinities for metal ions. It has been theorized that siderophores and weak organic ligands play a synergistic role during the transport of micronutrients in the rhizosphere, but the geochemical controls of this process remain unknown. Here we test the hypothesis that gradients in pH and ion strength regulate and enable the cooperation. To this end, first we use potentiometric titrations to identify the dominant Zn(II)–Cit and Zn(II)–DFOB complexes and to determine their ionic strength dependent stability constants between 0 and 1 mol dm−3. We parametrise the Extended Debye-Hückel (EDH) equation and determine accurate intrinsic association constants (logβ0) for the formation of the complexes present. The speciation model developed confirms the presence of [Zn(Cit)]−, [Zn(HCit)], [Zn2(Cit)2(OH)2]4−, and [Zn(Cit)2]4−, with [Zn(Cit)]− and [Zn2(Cit)2(OH)2]4− the dominant species in the pH range relevant to rhizosphere. We propose the existence of a new [Zn(Cit)(OH)3]4− complex above pH 10. We also verify the existence of two hexadentate Zn(II)–DFOB species, i.e., [Zn(DFOB)]− and [Zn(HDFOB)], and of one tetradentate species [Zn(H2DFOB)]+. Second, we identify the pH and ionic strength dependent ligand exchange points (LEP) of Zn with citrate and DFOB and the stability windows for Zn(II)–Cit and Zn(II)–DFOB complexes in NaCl and rice soil solutions. We find that the LEPs fall within the pH and ionic strength gradients expected in rhizospheres and that the stability windows for Zn(II)–citrate and Zn(II)–DFOB, i.e., low and high affinity ligands, can be distinctly set off. This suggests that pH and ion strength gradients allow for Zn(II) complexes with citrate and DFOB to dominate in different parts of the rhizosphere and this explains why mixtures of low and high affinity ligands increase leaching of micronutrients in soils. Speciation models of soil solutions using newly determined association constants demonstrate that the presence of dissolved organic matter and inorganic ligands (i.e., bicarbonate, phosphate, sulphate, or chlorides) do neither affect the position of the LEP nor the width of the stability windows significantly. In conclusion, we demonstrate that cooperative and synergistic ligand interaction between low and high affinity ligands is a valid mechanism for controlling zinc transport in the rhizosphere and possibly in other environmental reservoirs such as in the phycosphere. Multiple production of weak and strong ligands is therefore a valid strategy of plants and other soil organisms to improve access to micronutrients.

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“…The dependence of the stability constants on temperature, modeled by the TSTACO computer program, 47 is based on the van't Hoff equation:…”

Section: ■ Introductionmentioning

confidence: 99%

Thermodynamic Data for the Modeling of Lanthanoid(III) Sequestration by Reduced Glutathione in Aqueous Solution

et al. 2014

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This contribution reports the results of an investigation on the speciation of various lanthanoid(III) cations (Ln 3+ ), namely, La 3+ , Nd 3+ , Sm 3+ , Eu 3+ , Gd 3+ , Dy 3+ , and Yb 3+ , in the presence of reduced glutathione (or simply glutathione, GSH), in NaCl (aq) at I = 0.15 mol·dm −3 and T = 298.15 K. GSH forms in all cases the same four species, namely, Ln(GSH)H 3 , Ln(GSH)H 2 , Ln(GSH)H, and Ln(GSH)OH, whose stability depends on the type of lanthanoid, although it is also possible to consider an average stability for a generic lanthanoid, at least for the protonated species. Measurements at different temperatures and ionic strengths for the La 3+ /GSH and Gd 3+ /GSH systems have also been performed, to evaluate their effect on the speciation of both GSH and the Ln 3+ cations. The dependence of the determined stability constants on I and T has been modeled by an extended Debye−Huckel type and by the van't Hoff equations. In this last case, the formation enthalpy changes of La 3+ /GSH species have also been determined. The stability constants obtained have been therefore used to quantify the sequestering ability of GSH toward the investigated cations, in different pH, ionic strength, and temperature conditions, by the calculation of several pL 0.5 parameters. Their analysis showed that, generally, the sequestering ability of GSH increases with increasing pH and decreases with increasing temperature, while the ionic strength has only a small effect. Finally, results obtained may be exploited for the evaluation of the speciation (and, therefore, of the sequestration) of any Ln 3+ cations in the presence of GSH in different conditions of T and I, like those featuring many natural waters and biological fluids.

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Speciation of tin(II) in aqueous solution: thermodynamic and spectroscopic study of simple and mixed hydroxocarboxylate complexes

Cited by 27 publications

References 27 publications

The Solution Behavior of Dopamine in the Presence of Mono and Divalent Cations: A Thermodynamic Investigation in Different Experimental Conditions

The Solution Behavior of Dopamine in the Presence of Mono and Divalent Cations: A Thermodynamic Investigation in Different Experimental Conditions

Synergistic use of siderophores and weak organic ligands during zinc transport in the rhizosphere controlled by pH and ion strength gradients

Thermodynamic Data for the Modeling of Lanthanoid(III) Sequestration by Reduced Glutathione in Aqueous Solution

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