Study on the Isotope fractionation of Zinc in Complexation with Macrocyclic Polyethers

Abstract

Isotope fractionation of Zn was studied via liquid-liquid extraction with aqueous phase of ZnCl 2 /HCl and organic phase of crown ethers(CEs), including benzo15-crown-5(B15C5), benzo-18-crown-6(B18C6) and Dicyclohexano-24-crown-8(DC24C8)/ 1,2-dichloroethane. The isotope enrichment factor (ɛ 66), expressed in permil notation, of the isotope pair 66 ZnÀ 64 Zn was found to be between À 0.24 and À 0.52 % in the order of enrichment: B15C5 � B18C6 > DC24C8. The magnitude of ɛ 66 was well explained by theoretical isotope fractionation factors obtained by density functional theory method for zinc chloride and ZnCl 2 /CE model molecules, and a thermochemical description that correlates ɛ 66 with the differences in Gibbs free energy(ΔG) of the exchange reaction, here termed δΔG, based on the mass differences of Zn isotopes involved. Finally, results suggest that ɛ 66 may be used as a diagnostic and metric of Zn metabolic derangement, such as in porphyrias.

Theoretical and Experimental Study on Vanadium Isotope Fractionation among Species Relevant to Geochemistry

“…As the trivalent metal uptake, , V­(III) citrates (Figure k,m) and photosiderofore (Figure n) were computed by referring to the Fe­(III) case . To investigate the divalent metal uptake, the V IV O 2+ –porphyrin complex was computed (Figure r) using the Zn­(II) case, in which Zn 2+ was substituted by V IV O 2+ . The optimized structure showed a square planar structure of V with four N-donors of the porphyrin ring (Figure p).…”

“…In each study, the isotope fractionation experimentally observed was well predicted by theoretical isotope fractionation factors, expressed as beta factors, ln β, obtained by the density functional theory (DFT) method for model molecules related to these systems. Hence, in the present study, we have experimentally determined the isotope fractionation factor, δ 51 V, the ratio of 51 V and 50 V ([ 51 V]/[ 50 V]), for a chemical exchange system with a crown ether, a macrocyclic compound, which engenders isotope fractionation among metals when equilibrated with an aqueous phase. − The experimental results were then compared to theoretical calculations determined by employing the DFT method using relevant V model molecules (inorganic species and organometallic species), and we show that the calculations and the experimental work provide comparable results. We then use our calculation method to provide the theoretical isotopic fractionation factor for various V molecules that are relevant to geological and biological environments.…”

“…Ligand exchange reactions of cations with macrocyclic polyethers have promise revealing isotope fractionations − with solvent extraction and liquid chromatography being the main experimental techniques. Factors such as the number and type of donors in the macrocycles, acidity, type of counter-anions, aqueous and organic solvents, and temperature have been found to influence isotope fractionation. − Some of us previously tested the solvent extraction of Zn , and Ni from HCl solutions by using a crown ether, dicyclohexano-18-crown-6 (DC18C6), and were able to successfully investigate the acidity dependence of possible isotope fractionation. These previous studies have demonstrated the high reproducibility of isotope fractionation factors with values less than the analytical uncertainty of mass spectrometry even in the presence of contamination from the experimental atmosphere. , Hence, using the well-examined MC–ICP–MS technique, we investigated the acidity dependence of V isotope fractionation in a laboratory-scale extraction system with DC18C6.…”

“…In the present study, the C−C stretching vibrational frequencies were also found in the wavenumber region of 900−1000 cm −1 , whereas C−O ones of 1000−1150 cm −1 is consistent with our previous study. 25 This suggests that the substitution of Zn 2+ by V IV O 2+ may not significantly change the stereochemical properties of the metal−DC18C6 complex. The ln β values obtained are shown in Table 3.…”

“…These previous studies have demonstrated the high reproducibility of isotope fractionation factors with values less than the analytical uncertainty of mass spectrometry even in the presence of contamination from the experimental atmosphere. 23,25 Hence, using the well-examined MC−ICP−MS technique, 29 we investigated the acidity dependence of V isotope fractionation in a laboratory-scale extraction system with DC18C6.…”