14280-50-3Relevant articles and documents
Chelating tendencies in the rows of polymeric sorbents and their copper(II) and lead(II) complexes
Basargin,Oskotskaya,Chebrova
, p. 1474 - 1477 (2007)
The physicochemical properties of chelating polymer sorbents (CPSs), derivatives of poly(styrene-2-hydroxy-1-azo-1-2-hydroxybenzene), are studied with respect to copper and lead ions. The following sorption parameters are determined: the optimum acidity, temperature, and duration; the sorption capacity of the sorbent (SCS); and stability constants of polychelates. Quantitative correlations are found between the dissociation constants (pK a) of the analytical functional group (AFG) of the sorbent, and the pH50 of chelation of the tested metals; between p Ka and the stability of the complexes (logβ); and between pKa and the charge of the oxygen atom of the complexing group (z); these correlations are intended for use in elucidating the effect of the structural features and acid-base properties of the AFG on the chemisorption parameters of copper(II) and lead(II). These correlations predict the physical-chemical properties of sorbents and the sorption parameters of trace elements for preconcentrating and separating them from biological, natural, and technical objects
Synthesis, characterization, and x-ray crystal structures of cyclam derivatives. 8. Thermodynamic and kinetic appraisal of lead(II) chelation by octadentate carbamoyl-armed macrocycles
Cuenot, Francois,Meyer, Michel,Espinosa, Enrique,Guilard, Roger
, p. 7895 - 7910 (2005)
En route toward the development of hybrid organic-inorganic extracting materials incorporating lead-selective chelators and their implementation in water purification processes, the lead(II) binding properties of three N-carbamoylmethyl-substituted 1,4,8,11-tetraazacyclotetradecanes (cyclams) have been fully investigated by spectroscopic (IR, UV-vis, MALDI-TOF MS, 1H and 13C NMR), X-ray crystallographic, potentiometric, and kinetic methods. Solution NMR studies revealed that the Pb2+ ion is entrapped in a molecular cage constituted by the four macrocyclic nitrogen and four amidic oxygen atoms. Protonation and lead binding constants determined in aqueous solution were shown to be linearly dependent, so that all three derivatives possess a similar affinity at any pH value. Thermodynamic and kinetic parameters revealed the crucial role played by the intramolecular hydrogen bonds also evidenced in the crystal structure of the tetraacetamide derivative L1, which involve the lone pair of each macrocyclic tertiary amine and one amidic hydrogen atom belonging to the appended arm. In contrast to L1, the absence of such intramolecular interactions for N-(dimethyl)carbamoylmethyl- and N-(diethyl)carbamoylmethyl-substituted cyclams (L2 and L3, respectively) accounts for the 2-3 orders of magnitude enhancement of their proton and lead binding affinities. Stopped-flow kinetic measurements enabled unraveling the formation process of the three lead(II) complexes that proceeds in a single rate-limiting step according to the Eigen-Winkler mechanism, while the apparent rate constants were found to increase in the order L3 2 ? L1 as a consequence of the more acidic character of L1. A common proton-assisted dissociation mechanism has been found for the three lead(II) complexes, which involves the rapid formation of a protonated, six-coordinate intermediate followed by either a unimolecular decomposition or a bimolecular attack of a second hydronium ion.
Bitskei, J.
, p. 259 - 262 (1957)
Preparation and properties of the corner-shared double cube [Mo6PbS8(H2O)18]8+ as a derivative of [Mo3S4(H2O)9]4+
Saysell, David M.,Huang,Sykes, A. Geoffrey
, p. 2623 - 2627 (2007/10/03)
The heterometallic corner-shared double-cuboidal cluster [Mo6PbS8(H2O)18]8+, with the lead atom common to both cubes, has been prepared for the first time by the reaction of [Mo3S4(H2O)9]4+ with lead shot, which requires up to 1 h to reach completion, and by addition of a solution mix of [Mo3S4(H2O)9]4+ and PbII to an excess of BH4-, when reaction is rapid. The air-sensitive blue-green product has UV/VIS absorbance bands at 387 and 757 nm in 2.0 M HClO4. Inductively coupled plasma atomic emission spectroscopy confirmed the Mo:Pb:S ratio as 6:1:8. It was eluted from a cation-exchange column with 4 M Hpts (toluene-p-sulfonic acid), but not 2 M Hpts (or 4 M HClO4), consistent with a high charge, confirmed as 8 + from the 2:1 stoichiometries for the oxidation reactions with e.g. [Co(dipic)2]- (dipic = pyridine-2,6-dicarboxylate) or [Fe(H2O)6]3+, which yield [Mo3S4(H2O)9]4+. Kinetic studies on the oxidations with [Co(dipic)2]- and [Fe(H2O)6]3+ were also carried out as part of an overall appraisal of the reactivity of the heterometallic clusters.
