摘要 :
The advances and problems associated with the synthesis, properties and structure of metal complexes based on chelating polymer ligands are presented and assessed. The polymeric metal chelates (PMCs) are divided into molecular, in...
展开
The advances and problems associated with the synthesis, properties and structure of metal complexes based on chelating polymer ligands are presented and assessed. The polymeric metal chelates (PMCs) are divided into molecular, intracomplex, macrocyclic and polynuclear types, which in turn are grouped according to the nature of the donor atoms (N,N-, N,D-, N,S-, D,D-, O,S-, S,S-, D ,D -chelates, etc.). The main attention is focused on the similarities and differences between low and high molecular weight metal chelates, as well as the spatial organization of PMCs. The most important areas of research in the field of such compounds are highlighted. Thermal transformations of metal complexes based on chelating polymer ligands leading to the formation of nanostructured materials are considered. The bibliography includes the articles published after 2010.
收起
摘要 :
This review summarizes recent advances in the chemistry of metal chelate monomers. Depending on the character of bonding of the metal to the chelating fragment, metal chelate monomers are divided into four main types: molecular me...
展开
This review summarizes recent advances in the chemistry of metal chelate monomers. Depending on the character of bonding of the metal to the chelating fragment, metal chelate monomers are divided into four main types: molecular metal chelates, intracomplex compounds, macrocyclic complexes, and polynuclear metal chelates. The synthetic methodologies for preparing metal chelate monomers are systematized. Special attention is paid to the effect of a metal on both the polymerization transformations of the metal chelate monomers and properties of the products formed. The bibliography includes papers published after 2010.
收起
摘要 :
The use of hydroxyl radical-based reaction (Fenton reaction) for the destruction of organic pollutants has been widely reported in the literature. However, low pH requirement, precipitate formation problem, and rapid peroxide cons...
展开
The use of hydroxyl radical-based reaction (Fenton reaction) for the destruction of organic pollutants has been widely reported in the literature. However, low pH requirement, precipitate formation problem, and rapid peroxide consumption rate make the application of conventional Fenton reaction difficult. A chelate-based Fenton reaction can prevent Fe(OH)_3 (s) precipitation even at neutral pH condition and reduce the H_2O_2 consumption rate by controlling Fe~(2+) concentration. The chelating agent combines with Fe~(2+) or Fe~(3+) to form stable metal-chelate complexes in solution. This decreases the concentration of Fe~(2+) in the solution so that reactions can be carried for longer contact times. The major objective of this study was to establish the role of the chelating agent and to obtain oxidation rates for various reaction conditions using a model chlorinated organic compound. Experimental results (with citrate as chelating agent) for 2,4,6-trichlorophenol (TCP) showed that the TCP dechlorinations were highly effective even at pH values > 5. Although the main focus of this research is the application of monomeric chelate (such as citrate) in the Fenton reaction, the role of polymeric chelate (such as polyacrylic acid) has also been explored. Rate models for the chelate-based Fenton reaction were developed by adding the effects of iron chelation chemistry along with the well-known OH· formation and decomposition kinetics.
收起
摘要 :
Metal ions and metal chelates have been extracted from both solid and aqueous matrices using both pure and modi lied supercritical fluid CO_2. It has been demonstrated that fluorinated chelates have higher solubility in the superc...
展开
Metal ions and metal chelates have been extracted from both solid and aqueous matrices using both pure and modi lied supercritical fluid CO_2. It has been demonstrated that fluorinated chelates have higher solubility in the supercritical fluid which can cause enhanced extraction efficiency. Stability of the neutral metal chelate under supercritical conditions plays an important role in the extraction of metal ions from water. Also, it has been demonstrated that the matrix can have a major effect on extraction of both metal ions and metal chelates. Addition of modifier to both matrix and supercritical fluid can increase extraction efficiency of analytes.
收起
摘要 :
Two olive mill wastewaters (OMW) samples, OMWa and OMWb, containing different polyphenolic loads were used for decontaminating an unauthorized dump site in the Campania region, south Italy. In a bench-scale experiment, OMWa at pH ...
展开
Two olive mill wastewaters (OMW) samples, OMWa and OMWb, containing different polyphenolic loads were used for decontaminating an unauthorized dump site in the Campania region, south Italy. In a bench-scale experiment, OMWa at pH 6.0 (OMWasH.) and 4.7 (OMWasH.), OMWb at pH 4.7 (OMWbsH.) and OMWa free of the polyphenolic moiety polyphenol-free OMWa (PF-OMWa) were added to the soil for a 96iu h contact time. At 96iu h, OMWasH. was more effective than OMWasH., with Cd, Cu, Pb and Zn removal percentages of 30.768.1. Cd and Pb levels were 6.0 and 915iu mgiu kgp#, respectively, decreasing below the regulatory limits for industrial and commercial areas (15.0 and 1iu ciu 10pd mgiu kgp#, respectively). A threefold decrease in Zn levels was also observed from 13.5iu ciu 10pd to 4.3iu ciu 10pdiu mgiu kgp#. The metal removal efficiency of PF-OMWa dropped from 30.7iu % to 15.6iu % for Cd and from 37.9iu % to 1.3iu % for Pb. OMWbsH. at 96iu h was more efficient than OMWasH., with mean removal percentages of 32.5 versus 7.8, respectively.
收起
摘要 :
Analysis of crystal structure data deposited in the Cambridge Structural Database (CSD) has shown that aromatic rings tend to stack with square planar transition metal complexes when they contain chelate rings. In these interactio...
展开
Analysis of crystal structure data deposited in the Cambridge Structural Database (CSD) has shown that aromatic rings tend to stack with square planar transition metal complexes when they contain chelate rings. In these interactions, the orientation between chelate and aryl ring is a parallel-displaced orientation, like stacking interactions between aromatic molecules. In fused systems containing chelate and aryl rings, the aryl rings prefer to stack with the chelate rather than with other aryl rings. Quantum chemical calculations show that chelate-aryl stacking is stronger than aryl-aryl stacking. Interaction energies of six-membered chelates of the acetylacetonato type with benzene exceed -6 kcal/mol (CCSD(T)/CBS), more that twice as strong as that for two benzene molecules. Further analysis of the CSD has shown that chelate rings, both isolated and fused stack with other chelate rings. These chelate-chelate stacking interactions can have both face-to-face and parallel-displaced geometries, unlike the stacking interactions between aromatic molecules, for which face-to-face geometry is not typical. Chelate-chelate stacking is stronger than aryl-aryl stacking and stronger even than chelate-aryl stacking. Stacking energies between six-membered chelates of acetylacetonato type exceed -9 kcal/mol, while those between five-membered dithiolene chelates are even stronger. Calculated interaction energies and analysis of supramolecular structures have shown that chelate-chelate and chelate-aryl stacking must be considered in understanding the packing and organization of supramolecular systems and crystal engineering. (C) 2017 Elsevier B.V. All rights reserved.
收起
摘要 :
Mixed ligand transition metal (Co~(2centre dot) and Ni~(2centre dot)) compelxes having general formula ML_2, HL~1 have been synthesised and characterised on the basis of various physico-chemical measurements i.e. IR spectral data,...
展开
Mixed ligand transition metal (Co~(2centre dot) and Ni~(2centre dot)) compelxes having general formula ML_2, HL~1 have been synthesised and characterised on the basis of various physico-chemical measurements i.e. IR spectral data, UV spectra, magnetic and conductance measurements. The above study reveals the octahedral geometry of the compelxes.
收起
摘要 :
This article reviews the clinical use of the metal chelators sodium 2,3-dimercapto-1-propanesulfonate (DMPS), meso-2,3-dimercaptosuccinic acid (DMSA), and calcium disodium edetate (CaEDTA, calcium EDTA) in overexposure and poisoni...
展开
This article reviews the clinical use of the metal chelators sodium 2,3-dimercapto-1-propanesulfonate (DMPS), meso-2,3-dimercaptosuccinic acid (DMSA), and calcium disodium edetate (CaEDTA, calcium EDTA) in overexposure and poisonings with salts of lead (Pb), mercury (Hg), and arsenic (As). DMSA has considerably lower toxicity than the classic heavy metal antagonist BAL (2,3-dimercaptopropanol) and is also less toxic than DMPS. Because of its adverse effects, CaEDTA should be replaced by DMSA as the antidote of choice in treating moderate Pb poisoning. Combination therapy with BAL and CaEDTA was previously recommended in cases of severe acute Pb poisoning with encephalopathy. We suggest that BAL in such cases acted as a shuttling Pb transporter from the intra- to the extracellular space. The present paper discusses if a combination of the extracellularly distributed DMSA with the ionophore, Monensin may provide a less toxic combination for Pb mobilization by increasing both the efflux of intracellularly deposited Pb and the urinary Pb excretion. Anyhow, oral therapy with DMSA should be continued with several intermittent courses. DMPS and DMSA are also promising antidotes in Hg poisoning, whereas DMPS seems to be a more efficient agent against As poisoning. However, new insight indicates that a combination of low-dosed BAL plus DMPS could be a preferred antidotal therapy to obtain mobilization of the intracerebral deposits into the circulation for subsequent rapid urinary excretion.
收起
摘要 :
In the past decade, food-derivedmetal-chelating peptides (MCPs) have attracted
significant attention from researchers working towards the prevention of metal
(viz., iron, zinc, and calcium) deficiency phenomenon by primarily inh...
展开
In the past decade, food-derivedmetal-chelating peptides (MCPs) have attracted
significant attention from researchers working towards the prevention of metal
(viz., iron, zinc, and calcium) deficiency phenomenon by primarily inhibiting
the precipitation of metals caused by the gastrointestinal environment and
exogenous substances (including phytic and oxalic acids). However, for the
improvement of limits of current knowledge foundations and future investigation
directions of MCP or their derivatives, several review categories should
be improved and emphasized. The species’ uniqueness and differences in MCP
productions highly contribute to the different values of chelating ability with
particular metal ions, whereas comprehensive reviews of chelation characterization
determined by various kinds of technique support different horizons for
explaining the chelation and offer options for the selection of characterization
methods. The reviews of chelation mechanism clearly demonstrate the involvement
of potential groups and atoms in chelating metal ions. The discussions of
digestive stability and absorption in various kinds of absorption model in vitro
and in vivo as well as the theory of involved cellular absorption channels and
pathways are systematically reviewed and highlighted compared with previous
reports as well. Meanwhile, the chelation mechanism on the molecular docking
level, the binding mechanism in amino acid identification level, the utilizations
of everted rat gut sac model for absorption, and the involvement of cellular
absorption channels and pathway are strongly recommended as novelty in this
review. This review makes a novel contribution to the literature by the comprehensive
prospects for the research and development of food-derived mineral
supplements.
收起
摘要 :
The National Center for Health Statistics estimates that more than 100,000 Americans receive chelation each year, although far fewer than 1 % of these cases are managed by medical toxicologists. Unfortunately, fatalities have been...
展开
The National Center for Health Statistics estimates that more than 100,000 Americans receive chelation each year, although far fewer than 1 % of these cases are managed by medical toxicologists. Unfortunately, fatalities have been reported after inappropriate chelation use. There are currently 11 FDA-approved chelators available by prescription although chelation products may also be obtained through compounding pharmacies and directly over the internet. Promotion of chelation training is prominent on some alternative and complementary medicine websites.
收起
原文获取