Determination of the stability constants of mercury(ii) complexes of mixed donor macrobicyclic encapsulating ligands†

Sharrad, Clint A.; Grøndahl, Lisbeth; Gahan, Lawrence R.

doi:10.1039/b103706b

Cited by 8 publications

(2 citation statements)

References 19 publications

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“…Mixed-donor N/S sar ligands have been reported (Scheme 1) that comprise combinations such as (N 3 S 3 ), [4][5][6][7] (N 4 S 2 ), [8][9][10][11] and (N 5 S) [12,13] donor atoms, accessible through Co III -directed chemistry of suitably configured, preformed, mixed-donor (N/S) acyclic hexadentate ligands. Complexes of AMME-N 3 S 3 sar (Scheme 1) are the most extensively studied of all N/S mixed-donor cage ligands from this family, and their Co III , [4][5][6][14][15][16] Fe II , [17] and Hg II [18] complexes all exhibit the expected N 3 S 3 hexadentate coordination mode.…”

Section: Introductionmentioning

confidence: 99%

Copper(II) Complexes of a Hexadentate Mixed‐Donor N₃S₃ Macrobicyclic Cage: Facile Rearrangements and Interconversions

Bell

Bernhardt

Gahan

et al. 2010

Chemistry A European J

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The potentially hexadentate mixed-donor cage ligand 1-methyl-8-amino-3,13,16-trithia-6,10,19-triazabicyclo[6.6.6]eicosane (AMME-N(3)S(3)sar; sar=sarcophagine) displays variable coordination modes in a complex with copper(II). In the absence of coordinating anions, the ligand adopts a conventional hexadentate N(3)S(3) binding mode in the complex [Cu(AMME-N(3)S(3)sar)](ClO(4))(2) that is typical of cage ligands. This structure was determined by X-ray crystallography and solution spectroscopy (EPR and NIR UV/Vis). However, in the presence of bromide ions in DMSO, clean conversion to a five-coordinate bromido complex [Cu(AMME-N(3)S(3)sar)Br](+) is observed that features a novel tetradentate (N(2)S(2))-coordinated form of the cage ligand. This copper(II) complex has also been characterized by X-ray crystallography and solution spectroscopy. The mechanism of the reversible interconversion between the six- and five-coordinated copper(II) complexes has been studied and the reaction has been resolved into two steps; the rate of the first is linearly dependent on bromide ion concentration and the second is bromide independent. Electrochemistry of both [Cu(AMME-N(3)S(3)sar)](2+) and [Cu(AMME-N(3)S(3)sar)Br](+) in DMSO shows that upon reduction to the monovalent state, they share a common five-coordinated form in which the ligand is bound to copper in a tetradentate form exclusively, regardless of whether a six- or five-coordinated copper(II) complex is the precursor.

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Section: Introductionmentioning

confidence: 99%

Copper(II) Complexes of a Hexadentate Mixed‐Donor N₃S₃ Macrobicyclic Cage: Facile Rearrangements and Interconversions

Bell

Bernhardt

Gahan

et al. 2010

Chemistry A European J

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“…[7] In order to evaluate the extent of complexation of metal ions with the functionalized nanoparticles at such low concentrations, metal radioisotopes have been employed. The radioisotopes employed in this study were Hg-197/Hg-203 and Co-57, the choice dictated in part by their different ionic radii (Hg II : 102 pm; Co II : 74 pm; Co III : 61 pm), their propensity for coordination to these types of macrobicyclic ligand, [8][9][10][11] …”

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Surface‐Functionalized Polymer Nanoparticles for Selective Sequestering of Heavy Metals

et al. 2006

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In this communication, we demonstrate the synthesis of surface-functionalized polymer nanoparticles for the selective sequestering of heavy metals. This is the first example where the reversible addition-fragmentation chain transfer (RAFT; xanthate, 1) end groups on the surface of the particles can not only be utilized to control the molecular weight, block-copolymer formation, and particle morphology, but also aid in the selective binding to Hg II over Co II at low concentrations (below parts per million, ppm). Mercury, lead, and cadmium are considered harmful to humans, as they inhibit enzymatic processes because of their strong interactions with cystine residues to form secondary macromolecular structures. We have sought a methodology for the preparation of new nanoscale materials for the selective removal of heavy-metal ions from water at below ppm levels. The synthesis was carried out using RAFT emulsion polymerization to create novel polymer nanoparticles dispersed in water with controlled molecular weight and particle morphology. [1][2][3][4] The advantage of the approach is that the use of xanthates (1) (RAFT agents shown to be located at the polymer/water interface) [2,5] as the controlling agent permits the polymer to grow from the interface and enables the production of core/shell-type morphologies and thus controlled surface functionality (Scheme 1).In this work, we synthesized a block-copolymer particle consisting of a polystyrene (PSTY) core and a thin shell of poly((2-acetoacetoxy)ethyl methacrylate) (polyAAEMA). The side chain of polyAAEMA has ketone functionality [2] that can be coupled with metal-binding ligands to produce a surface-functionalized nanoparticle. The choice of ligand is dictated in part by the capacity of the ligand to be selective for a particular type of metal ion. We have chosen to employ a macrobicyclic ligand (NH 2 capten, 2, Scheme 1) containing both secondary amine (r donor) and thioether (p acceptor) metal-coordination sites as well as a suitably positioned amine functionality for attachment to the nanoparticle (Scheme 1). [7] In order to evaluate the extent of complexation of metal ions with the functionalized nanoparticles at such low concentrations, metal radioisotopes have been employed. The radioisotopes employed in this study were The ab-initio emulsion polymerization of styrene in the presence of the xanthate was carried out as reported previously. [2,5] The number-average molecular weight, M n , was equal to 41 917, and a polydispersity index (PDI) of 2.22 was measured by size exclusion chromatography. The resulting latex was dialyzed for three days, and the particle size of 73 nm was measured by dynamic light scattering. These results are consistent with previous findings. [1,3] The polystyrene latex was then used in a second-stage (seeded) emulsion polymerization to make nanoparticles, in which the second block (2 wt.-%) consisted of AAEMA. The M n increased to 42 786, and the PDI decreased to 2.17, based on a polystyrene calibration curve. The increase in M n a...

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Mercury(II) Complexes with Thiacrowns and Related Macrocyclic Ligands

Grant¹

Recent Developments in Mercury Science

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Determination of the stability constants of mercury(ii) complexes of mixed donor macrobicyclic encapsulating ligands†

Cited by 8 publications

References 19 publications

Copper(II) Complexes of a Hexadentate Mixed‐Donor N₃S₃ Macrobicyclic Cage: Facile Rearrangements and Interconversions

Copper(II) Complexes of a Hexadentate Mixed‐Donor N₃S₃ Macrobicyclic Cage: Facile Rearrangements and Interconversions

Surface‐Functionalized Polymer Nanoparticles for Selective Sequestering of Heavy Metals

Mercury(II) Complexes with Thiacrowns and Related Macrocyclic Ligands

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Determination of the stability constants of mercury(ii) complexes of mixed donor macrobicyclic encapsulating ligands†

Cited by 8 publications

References 19 publications

Copper(II) Complexes of a Hexadentate Mixed‐Donor N3S3 Macrobicyclic Cage: Facile Rearrangements and Interconversions

Copper(II) Complexes of a Hexadentate Mixed‐Donor N3S3 Macrobicyclic Cage: Facile Rearrangements and Interconversions

Surface‐Functionalized Polymer Nanoparticles for Selective Sequestering of Heavy Metals

Mercury(II) Complexes with Thiacrowns and Related Macrocyclic Ligands

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Copper(II) Complexes of a Hexadentate Mixed‐Donor N₃S₃ Macrobicyclic Cage: Facile Rearrangements and Interconversions

Copper(II) Complexes of a Hexadentate Mixed‐Donor N₃S₃ Macrobicyclic Cage: Facile Rearrangements and Interconversions