Spectroscopic speciation of aqueous Am(iii)-oxalate complexes

H. K. Kim, K. Jeong, H. R. Cho, E. C. Jung, Kyungwon Kwak, W. Cha

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

Transportation of actinides through the geosphere is facilitated by complexation with organic ligands dissolved in groundwater. Carboxylic groups can interact directly with actinide ions and are found among the most abundant organic ligands in alkaline aquatic systems like underground water. In this study, the complexation of organic carboxylic groups with Am(iii) was investigated by monitoring the interactions of Am(iii) with oxalate (Ox), the simplest dicarboxylate ligand, in solution. UV-Vis spectrophotometry coupled with a liquid waveguide capillary cell (100 cm optical path-length) and time-resolved laser fluorescence spectroscopy were employed for quantitative detection of the respective Am(iii)-Ox species. Increasing the Ox concentration caused significant spectral changes, i.e., red-shifts in both the absorption and luminescence maxima with increased molar absorption coefficients, enhanced luminescence intensities, and prolonged luminescence lifetimes. Individual spectra of AmOx+(aq), Am(Ox)2-(aq), and Am(Ox)33-(aq) were resolved by deconvolution of the absorption spectra, with apparent formation constants of logβ1,1 = 5.34 ± 0.05, logβ1,2 = 9.14 ± 0.18, and logβ1,3 = 11.49 ± 0.30, respectively, in I = 0.1 M NaClO4 and 0-30 mM Na2Ox. The absorption and luminescence spectral changes suggest bidentate complexation of Ox with Am(iii) via inner-sphere interactions. The geometry of the Am(iii)-Ox complexes was optimized by density functional theory, where the bonding characteristics were in good agreement with the experimental results. Thorough spectroscopic characterization enabled speciation of the Am(iii)-Ox complexes and determination of their formation constants. This spectroscopic approach is generally applicable in the investigation of molecular interactions between Am(iii) and various ligands in aqueous solution.

Original languageEnglish
Pages (from-to)10023-10032
Number of pages10
JournalDalton Transactions
Volume48
Issue number27
DOIs
Publication statusPublished - 2019 Jan 1

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Oxalates
Luminescence
Complexation
Actinoid Series Elements
Ligands
Groundwater
Laser spectroscopy
Molecular interactions
Spectrophotometry
Fluorescence Spectrometry
Fluorescence spectroscopy
Deconvolution
Density functional theory
Absorption spectra
Waveguides
Lasers
Ions
Geometry
Monitoring
Liquids

ASJC Scopus subject areas

  • Inorganic Chemistry

Cite this

Kim, H. K., Jeong, K., Cho, H. R., Jung, E. C., Kwak, K., & Cha, W. (2019). Spectroscopic speciation of aqueous Am(iii)-oxalate complexes. Dalton Transactions, 48(27), 10023-10032. https://doi.org/10.1039/c9dt01087d

Spectroscopic speciation of aqueous Am(iii)-oxalate complexes. / Kim, H. K.; Jeong, K.; Cho, H. R.; Jung, E. C.; Kwak, Kyungwon; Cha, W.

In: Dalton Transactions, Vol. 48, No. 27, 01.01.2019, p. 10023-10032.

Research output: Contribution to journalArticle

Kim, HK, Jeong, K, Cho, HR, Jung, EC, Kwak, K & Cha, W 2019, 'Spectroscopic speciation of aqueous Am(iii)-oxalate complexes', Dalton Transactions, vol. 48, no. 27, pp. 10023-10032. https://doi.org/10.1039/c9dt01087d
Kim, H. K. ; Jeong, K. ; Cho, H. R. ; Jung, E. C. ; Kwak, Kyungwon ; Cha, W. / Spectroscopic speciation of aqueous Am(iii)-oxalate complexes. In: Dalton Transactions. 2019 ; Vol. 48, No. 27. pp. 10023-10032.
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