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Thermodynamic stability of mercury(II) complexes formed with environmentally relevant low-molecular-mass thiols studied by competing ligand exchange and density functional theory

Liem-Nguyen, Van and Skyllberg, Ulf and Kwangho, Nam and Björn, Erik (2017). Thermodynamic stability of mercury(II) complexes formed with environmentally relevant low-molecular-mass thiols studied by competing ligand exchange and density functional theory. Environmental Chemistry. 14:4, 243-253
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Official URL: http://dx.doi.org/10.1071/EN17062

Abstract

Inorganic divalent mercury (Hg-II) has a very high affinity for reduced sulfur functional groups. Reports from laboratory experiments suggest that Hg-II complexes with specific low-molecular-mass (LMM) thiol (RSH) ligands control rates of Hg-II transformation reactions. Because of methodological limitations for precise determination of the highly stable Hg-II complexes with LMM thiol ligands, constants reported in the literature remain inconsistent. This uncertainty impedes accurate modelling of the chemical speciation of Hg-II and the possibility to elucidate the role of Hg-II complexes with LMM thiols for Hg transformation reactions. Here, we report values of thermodynamic stability constants for 15 monodentate, two-coordinated Hg-II complexes, Hg(SR)(2), formed with biogeochemically relevant LMM thiol ligands. The constants were determined by a two-step ligand-exchange procedure where the specific Hg(SR)(2) complexes were quantified by liquid chromatography-inductively coupled plasma mass spectrometry. Thermodynamic stability constants (log (2)) determined for the Hg(SR)(2) complexes ranged from 34.6, N-cysteinylglycine, to 42.1, 3-mercaptopropionic acid, for the general reaction Hg2++2RS(-) Hg(SR)(2). Density functional theory (DFT) calculations showed that electron-donating carboxyl and carbonyl groups have a stabilising effect on the Hg-II-LMM thiol complexes, whereas electron-withdrawing protonated primary amino groups have a destabilising effect. Experimental results and DFT calculations demonstrated that the presence of such functional groups in the vicinity of the RSH group caused significant differences in the stability of Hg(SR)(2) complexes. These differences are expected to be important for the chemical speciation of Hg-II and its transformation reactions in environments where a multitude of LMM thiol compounds are present.

Authors/Creators:Liem-Nguyen, Van and Skyllberg, Ulf and Kwangho, Nam and Björn, Erik
Title:Thermodynamic stability of mercury(II) complexes formed with environmentally relevant low-molecular-mass thiols studied by competing ligand exchange and density functional theory
Series/Journal:Environmental Chemistry (1449-8979)
Year of publishing :2017
Volume:14
Number:4
Page range:243-253
Number of Pages:11
Publisher:CSIRO Publishing
ISSN:1449-8979
Language:English
Publication Type:Journal article
Refereed:Yes
Article category:Scientific peer reviewed
Version:Accepted version
Full Text Status:Public
Agris subject categories.:X Agricola extesions > X50 Chemistry
Subjects:(A) Swedish standard research categories 2011 > 1 Natural sciences > 104 Chemical Sciences > Organic Chemistry
Keywords:Alkaline Aqueous-Solution, Nuclear Magnetic-Resonance, Human-Erythrocytes, Amino-Acids, Methylation, Glutathione, Cysteine, Constants, Hg(Ii), Thermochemistry
URN:NBN:urn:nbn:se:slu:epsilon-e-4795
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-e-4795
Additional ID:
Type of IDID
Web of Science (WoS)000406229200006
ID Code:14887
Faculty:S - Faculty of Forest Sciences
Department:(S) > Dept. of Forest Ecology and Management
Deposited By: SLUpub Connector
Deposited On:08 Mar 2018 08:43
Metadata Last Modified:08 Mar 2018 08:43

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