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

Sharrad, C. A., Grondahl, L. and Gahan, L. R. (2001) Determination of the stability constants of mercury(II) complexes of mixed donor macrobicyclic encapsulating ligands. Journal of the Chemical Society. Dalton transactions., 36 19: 2937-2942. doi:10.1039/b103706b


Author Sharrad, C. A.
Grondahl, L.
Gahan, L. R.
Title Determination of the stability constants of mercury(II) complexes of mixed donor macrobicyclic encapsulating ligands
Journal name Journal of the Chemical Society. Dalton transactions.
ISSN 1472-7773
Publication date 2001-01-01
Year available 2001
Sub-type Article (original research)
DOI 10.1039/b103706b
Open Access Status Not yet assessed
Volume 36
Issue 19
Start page 2937
End page 2942
Total pages 6
Place of publication Cambridge
Publisher Royal Soc Chemistry
Language eng
Subject 03 Chemical Sciences
Abstract The reactions of mercury(II) with the mixed donor encapsulating ligands 3,6,16-trithia-6,11,19-triazabicyclo[6.6.6]icosane (AMN(3)S(3)sar) and 1-amino-8-methyl-6,19-dithia-3,10,13,16-tetraazabicyclo[6.6.6]icosane (AMN(4)S(2)sar) have been studied. NMR ligand-ligand competition experiments with the ligands 1,4,8,11-tetraazaeyclotetradecane ([14]aneN(4)), 1-thia-4,7,10-triazacyclododecane ([12]aneN(3)S) and ethylenediaminetetraacetic acid (EDTA) with AMN(3)S(3)sar and Hg(II) indicated that [14]aneN(4) would be an appropriate competing ligand for the, determination of the Hg(II) stability constant. Calculations indicated the ratio of concentrations of AMN3S3sar, [14]aneN(4) and Hg(II) required for the determination of the stability constant ranged from 1:1:1 to 1:5:1. Refinement of the titration curves yielded log(10)K[Hg(AMN(3)S(3)sar)](2+) = 17.7. A similar competition titration resulted in the determination of the stability constant for the AMN(4)S(2)sar system as log(10)K[Hg(AMN(4)S(2)sar)](2+) = 19.5. The observed binding constants for the mixed N/S donor systems and the hexaaza analogues sar (3,6,10,13,16,19-hexaazabicyclo [6.6.6]icosane) and diamsar (1,8-diamino-3,6,10,13,16,19 -hexazabicyclo [6.6.6] icosane (log(10)K-[Hg(diamsar)](2+) = 26.4; log(10)K[Hg(sar)](2+) = 28.1) differ by approximately ten orders of magnitude. The difference is ascribed not to a cryptate effect but to a mismatch in the Hg-N and Hg-S bond lengths in the N/S systems.
Keyword Chemistry, Inorganic & Nuclear
Macrocyclic Complexes
Cobalt(ii) Complexes
Metal-ions
Spectroscopy
Enterobactin
Acid
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Unknown

Document type: Journal Article
Sub-type: Article (original research)
Collection: School of Chemistry and Molecular Biosciences
 
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Created: Mon, 13 Aug 2007, 22:38:09 EST