Unsaturated Sulfur Crown Ethers Can Extract Mercury(II) and Show Promise for Future Copernicium(II) Studies: A Combined Experimental and Computational Study

Maryline G. Ferrier; Carlos A. Valdez; Saurabh Kumar Singh; Saphon Hok; Debmalya Ray; Laura Gagliardi; John D. Despotopulos

doi:10.1021/acs.inorgchem.1c01869

Unsaturated Sulfur Crown Ethers Can Extract Mercury(II) and Show Promise for Future Copernicium(II) Studies: A Combined Experimental and Computational Study

Maryline G. Ferrier, Carlos A. Valdez, Saurabh Kumar Singh, Saphon Hok, Debmalya Ray, Laura Gagliardi, John D. Despotopulos

Research output: Contribution to journal › Article › peer-review

2 Scopus citations

Abstract

The unsaturated hexathia-18-crown-6 (UHT18C6) molecule was investigated for the extraction of Hg(II) in HCl and HNO3 media. This extractant can be directly compared to the recently studied saturated hexathia-18-crown-6 (HT18C6). The default conformation of the S lone pairs in UHT18C6 is endodentate, where the pocket of the charge density, according to the crystal structures, is oriented toward the center of the ring, which should allow better extraction for Hg(II) compared to the exodentate HT18C6. Batch study experiments showed that Hg(II) had better extraction at low acid molarity (ca. 99% in HCl and ca. 95% in HNO3), while almost no extraction was observed above 0.4 M HCl and 4 M HNO3 (<5%). Speciation studies were conducted with the goal of delineating a plausible extraction mechanism. Density functional theory calculations including relativistic effects were carried out on both Hg(II)-encapsulated HT18C6 and UHT18C6 complexes to shed light on the binding strength and the nature of bonding. Our calculations offer insights into the extraction mechanism. In addition to Hg(II), calculations were performed on the hypothetical divalent Cn(II) ion, and showed that HT18C6 and UHT18C6 could extract Cn(II). Finally, the extraction kinetics were explored to assess whether this crown can extract the short-lived Cn(II) species in a future online experiment.

Original language	English
Pages (from-to)	807-817
Number of pages	11
Journal	Inorganic Chemistry
Volume	61
Issue number	2
DOIs	https://doi.org/10.1021/acs.inorgchem.1c01869
State	Published - Jan 17 2022
Externally published	Yes

Funding

This study was performed under the auspices of the U.S. Department of Energy by LLNL under Contract DE-AC52-07NA27344. This work was funded by the Laboratory and Development Program at LLNL under Project 19-ERD-003. This material is based upon work supported by the Department of Energy National Nuclear Security Administration through the Nuclear Science and Security Consortium under Award DE-NA0003180. The computational part of this work was funded by the Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences, U.S. Department of Energy, through Grant DE-SC002183 (to L.G. and D.R.). S.K.S. acknowledges the Department of Science and Technology for the Start-up Research Grant SRG/2020/001323 and IIT Hyderabad for generous funding. The authors thank the CAMS facility staff at LLNL, specifically Scott Tumey, Thomas Brown, and Grahm Bench for providing beam time and expertise to the production of radionuclides used in this study. Calculations were performed at the Minnesota Supercomputing Institute.

Funders	Funder number
IIT Hyderabad
Laboratory and Development Program	19-ERD-003
U.S. Department of Energy
Basic Energy Sciences	DE-SC002183
National Nuclear Security Administration	DE-NA0003180
Lawrence Livermore National Laboratory	DE-AC52-07NA27344
Chemical Sciences, Geosciences, and Biosciences Division
Department of Science and Technology, Ministry of Science and Technology, India	SRG/2020/001323

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10.1021/acs.inorgchem.1c01869

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title = "Unsaturated Sulfur Crown Ethers Can Extract Mercury(II) and Show Promise for Future Copernicium(II) Studies: A Combined Experimental and Computational Study",

abstract = "The unsaturated hexathia-18-crown-6 (UHT18C6) molecule was investigated for the extraction of Hg(II) in HCl and HNO3 media. This extractant can be directly compared to the recently studied saturated hexathia-18-crown-6 (HT18C6). The default conformation of the S lone pairs in UHT18C6 is endodentate, where the pocket of the charge density, according to the crystal structures, is oriented toward the center of the ring, which should allow better extraction for Hg(II) compared to the exodentate HT18C6. Batch study experiments showed that Hg(II) had better extraction at low acid molarity (ca. 99% in HCl and ca. 95% in HNO3), while almost no extraction was observed above 0.4 M HCl and 4 M HNO3 (<5%). Speciation studies were conducted with the goal of delineating a plausible extraction mechanism. Density functional theory calculations including relativistic effects were carried out on both Hg(II)-encapsulated HT18C6 and UHT18C6 complexes to shed light on the binding strength and the nature of bonding. Our calculations offer insights into the extraction mechanism. In addition to Hg(II), calculations were performed on the hypothetical divalent Cn(II) ion, and showed that HT18C6 and UHT18C6 could extract Cn(II). Finally, the extraction kinetics were explored to assess whether this crown can extract the short-lived Cn(II) species in a future online experiment.",

author = "Ferrier, {Maryline G.} and Valdez, {Carlos A.} and Singh, {Saurabh Kumar} and Saphon Hok and Debmalya Ray and Laura Gagliardi and Despotopulos, {John D.}",

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AU - Valdez, Carlos A.

AU - Singh, Saurabh Kumar

AU - Hok, Saphon

AU - Ray, Debmalya

AU - Gagliardi, Laura

AU - Despotopulos, John D.

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AB - The unsaturated hexathia-18-crown-6 (UHT18C6) molecule was investigated for the extraction of Hg(II) in HCl and HNO3 media. This extractant can be directly compared to the recently studied saturated hexathia-18-crown-6 (HT18C6). The default conformation of the S lone pairs in UHT18C6 is endodentate, where the pocket of the charge density, according to the crystal structures, is oriented toward the center of the ring, which should allow better extraction for Hg(II) compared to the exodentate HT18C6. Batch study experiments showed that Hg(II) had better extraction at low acid molarity (ca. 99% in HCl and ca. 95% in HNO3), while almost no extraction was observed above 0.4 M HCl and 4 M HNO3 (<5%). Speciation studies were conducted with the goal of delineating a plausible extraction mechanism. Density functional theory calculations including relativistic effects were carried out on both Hg(II)-encapsulated HT18C6 and UHT18C6 complexes to shed light on the binding strength and the nature of bonding. Our calculations offer insights into the extraction mechanism. In addition to Hg(II), calculations were performed on the hypothetical divalent Cn(II) ion, and showed that HT18C6 and UHT18C6 could extract Cn(II). Finally, the extraction kinetics were explored to assess whether this crown can extract the short-lived Cn(II) species in a future online experiment.

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Unsaturated Sulfur Crown Ethers Can Extract Mercury(II) and Show Promise for Future Copernicium(II) Studies: A Combined Experimental and Computational Study

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