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 language | English |
|---|---|
| Pages (from-to) | 10023-10032 |
| Number of pages | 10 |
| Journal | Dalton Transactions |
| Volume | 48 |
| Issue number | 27 |
| DOIs | |
| Publication status | Published - 2019 Jan 1 |
Fingerprint
ASJC Scopus subject areas
- Inorganic Chemistry
Cite this
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 journal › Article
}
TY - JOUR
T1 - Spectroscopic speciation of aqueous Am(iii)-oxalate complexes
AU - Kim, H. K.
AU - Jeong, K.
AU - Cho, H. R.
AU - Jung, E. C.
AU - Kwak, Kyungwon
AU - Cha, W.
PY - 2019/1/1
Y1 - 2019/1/1
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=85068602880&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85068602880&partnerID=8YFLogxK
U2 - 10.1039/c9dt01087d
DO - 10.1039/c9dt01087d
M3 - Article
C2 - 31172147
AN - SCOPUS:85068602880
VL - 48
SP - 10023
EP - 10032
JO - Dalton Transactions
JF - Dalton Transactions
SN - 1477-9226
IS - 27
ER -