Lead-207 chemical shift data for bivalent lead compounds: thermodynamics of the equilibrium Pb(O2CCH3)2⇌[Pb(O2CCH3)]++ O2CCH3–in aqueous solution in the temperature range 303–323 K

Harrison, Philip G.; Healy, Michael A.; Steel, Andrew T.

doi:10.1039/dt9830001845

Cited by 42 publications

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“…It is sensitive to the local structure and electronic environment, the nature of surrounding donor atoms, the bond covalency and coordination number, and affected by temperature and concentration. 27, 28, 41–43 We measured 207 Pb NMR spectra for two sets of alkaline aqueous Pb(II)-cysteine solutions (containing 10% D 2 O), with increasing H 2 Cys/Pb(II) mole ratios (Table 1). Calculated distribution diagrams based on different sets of stability constants indicate that the dominating lead(II) complexes would be either [Pb(Cys) 2 ] 2− (Figure S-2b), 20 or a mixture of [Pb(Cys) 2 ] 2− and [Pb(Cys)(HCys)] − (Figure S-1b).…”

Section: Resultsmentioning

confidence: 99%

Lead(II) Complex Formation with l-Cysteine in Aqueous Solution

et al. 2015

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The lead(II) complexes formed with the multidentate chelator L-cysteine (H2Cys) in alkaline aqueous solution were studied using 207Pb, 13C and 1H NMR, Pb LIII-edge X-ray absorption and UV-vis. spectroscopic techniques, complemented by electro-spray ion mass spectrometry (ESI-MS). The H2Cys/Pb(II) mole ratios were varied from 2.1 to 10.0 for two sets of solutions with CPb(II) = 0.01 and 0.1 M, respectively, prepared at pH values (9.1 – 10.4) for which precipitates of Pb(II)-cysteine dissolved. At low H2Cys/Pb(II) mole ratios (2.1 – 3.0) a mixture of the dithiolate [Pb(S,N-Cys)2]2− and [Pb(S,N,O-Cys)(S-HCys)]− complexes with the average Pb-(N/O) and Pb-S distances 2.42 ± 0.04 Å and 2.64 ± 0.04 Å, respectively, was found to dominate. At high concentration of free cysteinate (> 0.7 M) a significant amount converts to the trithiolate [Pb(S,N-Cys)(S-HCys)2]2−, including a minor amount of a PbS3 coordinated [Pb(S-HCys)3]− complex. The coordination mode was evaluated by fitting linear combinations of EXAFS oscillations to the experimental spectra, and by the 207Pb NMR signals in the chemical shift range δPb = 2006 – 2507 ppm, which became increasingly deshielded with increasing free cysteinate concentration. One-pulse magic angle spinning (MAS) 207Pb NMR spectra of crystalline Pb(aet)2 (Haet = 2-aminoethanethiol or cysteamine) with PbS2N2 coordination were measured for comparison (δiso = 2105 ppm). The UV-vis. spectra displayed absorption maxima at 298 – 300 nm (S− → PbII charge transfer) for the dithiolate PbS2N(N/O) species; with increasing ligand excess a shoulder appeared at ∼ 330 nm for the trithiolate PbS3N and PbS3 (minor) complexes. The results provide spectroscopic fingerprints for structural models for Pb(II) coordination modes to proteins and enzymes.

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Section: Resultsmentioning

confidence: 99%

Lead(II) Complex Formation with l-Cysteine in Aqueous Solution

et al. 2015

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“…Table 1 shows that the end-over-end rotations of the nitrate anion are significantly affected by the cations Sc3+, La3+, pbZ+, s r 2 + , and c a 2 + even in a dilute solution of concentration 0.1 M in nitrate. The influence of the cation on nitrate anion rotations varies from being very small for H 3 0 + , NH4+, Li+, MgZ+, and z n 2 + to being very large for s c 3 + , La3+, and pb2+ where evidence for ion pairing was reported previously (24)(25)(26)(27)(28). These effects are a result of cation-anion and cation-and anion-solvent interactions, which retard rotations of the nitrate ion.…”

Section: Methodsmentioning

confidence: 97%

“…As already mentioned, the equilibrium constant for dissociation of Pb(N03)+ is known from 2 0 7~b nrnr (24), hence it is instructive to apply the above analysis to this system. The value of (TI).,, can be obtained by studying very dilute solutions.…”

Section: ( C ) Concentration Dependence Of ' 4~ Timentioning

confidence: 99%

A nuclear magnetic resonance study of aqueous solutions of several nitrate salts

Nicholas¹,

Wasylishen²

1987

Can. J. Chem.

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A. MARTIN DE P. NICHOLAS and RODER~CK E. WASYLISHEN. Can. J. Chem. 65, 951 (1987).Rotational correlation times for the end-over-end rotation of the C3 symmetry axis of the nitrate anion in the temperature range 3-80°C are studied by nuclear magnetic resonance spectroscopy for a variety of nitrate salts in aqueous solution. The counterion is found to retard the rotation of the anion in the following order: sc3+ > La3+ > pb2+ > Ca", s r 2 + > ~l~+ , K + , Nai, (CH3)?N+ > Zn2+, Mg2+, Li+, NH4+, H 3 0 + . This relative order is discussed in terms of the association of the nitrate ion with the cation. Oxygen-17 nmr spin-lattice relaxation times in combination with I4N nmr T I values are used to derive rotational diffusion constants for the in-plane rotations of the nitrate anion. In all cases the in-plane rotations are found to be slower than the corresponding end-over-end motion.A. MARTIN DE P. NICHOLAS et RODERICK E. WASYLISHEN. Can. J. Chem. 65, 951 (1987).Operant 21 des temperatures allant de 3 B 80°C et faisant appel a la spectroscopie rmn d'une variCt6 de nitrates en solution aqueuse, on a determine les temps de corrClation rotationnelle pour la rotation d'un bout j. l'autre de l'axe de rotation C3 de I'anion nitrate. On a trouvC que le contre ion retarde la rotation de l'anion dans l'ordre suivant : Sc3+ > La3+ > Pb2+ > Ca2+, Sr2+ > A I~' , K', Na+, (CH3),N+ > ~n " , M~~+ , Li', NH,', H30'. Ondiscute de cet ordre relatif enfonction de l'association de I'ion nitrate avec le cation. On a utilisC les temps de relaxation spin-rCseau de la rmn du 170 de concert avec les valeurs T I de la rmn du I4N pour obtenir les valeurs des constantes de diffusion rotationnelle pour les rotations dans le plan de l'anion nitrate.Dans tous les cas, on a trouve que les rotations dans le plan sont plus lentes que le mouvement correspondant d'un bout i l'autre.[Traduit par la revue] IntroductionNuclear magnetic resonance spectroscopy is one of several techniques available for studying the rotations of ions in solution (1-4). The ease of application and sensitivity of this method make it an attractive choice, especially for studying more dilute solutions. Recently we have shown (5) the importance of using I4N and 170 nmr spin-lattice relaxation measurements to studv the rotations of the nitrate and carbonate anions in aqueous solution in the presence of the sodium cation. We found rotations of the carbonate ion to be more hindered than those of the nitrate anion because of stronger cation-anion pairing and stronger anion-solvent interactions (hydrogen bonding). Some evidence for ion association was found for NaN03 at solute concentrations of 1 M; however, ion pairing is much more important for the divalent carbonate anion.

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“…Without attempting to titrate the pHs to a fixed value, the smectite suspensions equilibrated with solutions of different Pb concentrations exhibited an average (Harrison et al, 1983).…”

Section: Lead Sorption Isothermmentioning

confidence: 99%

Equilibrium and spectroscopic studies of lead retention in smectite

Shen

Taylor

Bart

et al. 1999

Communications in Soil Science and Plant Analysis

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Heavy metal pollution of soils and water is a serious environmental problem. Sorption onto solid surfaces from aqueous solutions is an important process influencing transport and accumulation of heavy metals in the environment. Lead (Pb) sorption in smectite SWy-2 was investigated by equilibrium sorption studies, coupled with spectroscopic methods. The isotherm and pH-edge of lead sorption in the smectite were measured in batch experiments. The sorption isotherms under uncontrolled pH were best-fitted with the Langmuir equation, while those with a fixed pH 5.5 were best-fitted with the Freundlich equation. The pH-edge of lead sorption shifted to a higher pH as the Pb concentration 1 Reference to a brand or firm name does not constitute endorsement by the U.S. Department of Agriculture over others of a similar nature not mentioned. 2712 SHEN ET AL.increased. The ionic strength only affected Pb sorption in the low pH range. The effects of associated nitrate and perchlorate anions were significant only for the Pb sorption at high Pb concentration (>2 mM). FTIR and XRD spectroscopies were performed with oriented clay samples. In the infrared spectra, apeak with a maximum near 1398 cm -1 and a shoulder centered near 1470 cm -1 was significant for the samples treated with >1 mM Pb at pH >5.6. This peak may be composed of several IR bands, including an OH bending band from Pb hydroxides and CO 3 2-stretching bands from Pb carbonates. The basal spacing of Pb-treated smectites increased with increasing Pb content in the clay and correlated well with the intensity of OH bending band (around 1621 cm -1 ) of adsorbed water. The increase of basal spacing at low pH (pH <3.3) was poorly correlated with the intensity of water OH bending band. The comprehensive studies provided many evidences for revealing the structure of various lead complexes on clay surfaces.

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Lead-207 chemical shift data for bivalent lead compounds: thermodynamics of the equilibrium Pb(O₂CCH₃)₂⇌[Pb(O₂CCH₃)]⁺+ O₂CCH₃^–in aqueous solution in the temperature range 303–323 K

Cited by 42 publications

References 0 publications

Lead(II) Complex Formation with l-Cysteine in Aqueous Solution

Lead(II) Complex Formation with l-Cysteine in Aqueous Solution

A nuclear magnetic resonance study of aqueous solutions of several nitrate salts

Equilibrium and spectroscopic studies of lead retention in smectite

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