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Title: Thermodynamic, spectroscopic, and computational studies of lanthanide complexation with Diethylenetriaminepentaacetic acide: temperature effect and coordination modes

Abstract

Stability constants of two DTPA (diethylenetriaminepentaacetic acid) complexes with lanthanides (ML2- and MHL-, where M stands for Nd and Eu and L stands for diethylenetriaminepentaacetate) at 10, 25, 40, 55, and 70 degrees C were determined by potentiometry, absorption spectrophotometry, and luminescence spectroscopy. The enthalpies of complexation at 25 degrees C were determined by microcalorimetry. Thermodynamic data show that the complexation of Nd3þ and Eu3þ with DTPA is weakened at higher temperatures, a 10-fold decrease in the stability constants of ML2- and MHL- as the temperature is increased from 10 to 70 degrees C. The effect of temperature is consistent with the exothermic enthalpy of complexation directly measured by microcalorimetry. Results by luminescence spectroscopy and density functional theory (DFT) calculations suggest that DTPA is octa-dentate in both the EuL2- and EuHL- complexes and, for the first time, the coordination mode in the EuHL- complex was clarified by integration of the experimental data and DFT calculations. In the EuHL- complex, the Eu is coordinated by an octa-dentate H(DTPA) ligand and a water molecule, and the protonation occurs on the oxygen of a carboxylate group.

Authors:
; ; ;
Publication Date:
Research Org.:
Idaho National Laboratory (INL)
Sponsoring Org.:
USDOE
OSTI Identifier:
1022750
Report Number(s):
INL/JOU-11-22944
Journal ID: ISSN 0020--1669; TRN: US201118%%444
DOE Contract Number:
DE-AC07-05ID14517
Resource Type:
Journal Article
Resource Relation:
Journal Name: Inorganic Chemistry; Journal Volume: 50; Journal Issue: 7
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ABSORPTION; ENTHALPY; FUNCTIONALS; LUMINESCENCE; OXYGEN; POTENTIOMETRY; RARE EARTHS; SPECTROPHOTOMETRY; SPECTROSCOPY; STABILITY; TEMPERATURE DEPENDENCE; THERMODYNAMICS; WATER; lanthanide complexation

Citation Formats

Guoxin Tian, Leigh R. Martin, Zhiyong Zhang, and Linfeng Rao. Thermodynamic, spectroscopic, and computational studies of lanthanide complexation with Diethylenetriaminepentaacetic acide: temperature effect and coordination modes. United States: N. p., 2011. Web. doi:10.1021/ic200025s.
Guoxin Tian, Leigh R. Martin, Zhiyong Zhang, & Linfeng Rao. Thermodynamic, spectroscopic, and computational studies of lanthanide complexation with Diethylenetriaminepentaacetic acide: temperature effect and coordination modes. United States. doi:10.1021/ic200025s.
Guoxin Tian, Leigh R. Martin, Zhiyong Zhang, and Linfeng Rao. 2011. "Thermodynamic, spectroscopic, and computational studies of lanthanide complexation with Diethylenetriaminepentaacetic acide: temperature effect and coordination modes". United States. doi:10.1021/ic200025s.
@article{osti_1022750,
title = {Thermodynamic, spectroscopic, and computational studies of lanthanide complexation with Diethylenetriaminepentaacetic acide: temperature effect and coordination modes},
author = {Guoxin Tian and Leigh R. Martin and Zhiyong Zhang and Linfeng Rao},
abstractNote = {Stability constants of two DTPA (diethylenetriaminepentaacetic acid) complexes with lanthanides (ML2- and MHL-, where M stands for Nd and Eu and L stands for diethylenetriaminepentaacetate) at 10, 25, 40, 55, and 70 degrees C were determined by potentiometry, absorption spectrophotometry, and luminescence spectroscopy. The enthalpies of complexation at 25 degrees C were determined by microcalorimetry. Thermodynamic data show that the complexation of Nd3þ and Eu3þ with DTPA is weakened at higher temperatures, a 10-fold decrease in the stability constants of ML2- and MHL- as the temperature is increased from 10 to 70 degrees C. The effect of temperature is consistent with the exothermic enthalpy of complexation directly measured by microcalorimetry. Results by luminescence spectroscopy and density functional theory (DFT) calculations suggest that DTPA is octa-dentate in both the EuL2- and EuHL- complexes and, for the first time, the coordination mode in the EuHL- complex was clarified by integration of the experimental data and DFT calculations. In the EuHL- complex, the Eu is coordinated by an octa-dentate H(DTPA) ligand and a water molecule, and the protonation occurs on the oxygen of a carboxylate group.},
doi = {10.1021/ic200025s},
journal = {Inorganic Chemistry},
number = 7,
volume = 50,
place = {United States},
year = 2011,
month = 4
}
  • The complexation of uranium(VI) and samarium(III) with oxydiacetate in 1.05 mol kg{sup -1} NaClO{sub 4} is studied at variable temperatures (25-70 C). Three U(VI)/O DA complexes (UO{sub 2}L, UO{sub 2}L{sub 2}{sup 2-}, and UO{sub 2}HL{sub 2}{sup -}) and three Sm(III)/ODA complexes (SmL{sub j}{sup (3-2j)+} with j = 1, 2, 3) are identified in this temperature range. The formation constants and the molar enthalpies of complexation are determined by potentiometry and calorimetry. The complexation of uranium(VI) and samarium(III) with oxydiacetate becomes more endothermic at higher temperatures. However, the complexes become stronger due to increasingly more positive entropy of complexation at highermore » temperatures that exceeds the increase in the enthalpy of complexation. The values of the heat capacity of complexation ({Delta}C{sub p}{sup o} in J K{sup -1} mol{sup -1}) are 95 {+-} 6, 297 {+-} 14, and 162 {+-} 19 for UO{sub 2}L, UO{sub 2}L{sub 2}{sup 2-}, and UO{sub 2}HL{sub 2}{sup -}, and 142 {+-} 6, 198 {+-} 14 and 157 {+-} 19 for SmL{sup +}, SmL{sub 2}{sup -}, and SmL{sub 3}{sup 3-}, respectively. The thermodynamic parameters, in conjunction with the structural information from spectroscopy, help to identify the coordination modes in the uranium oxydiacetate complexes. The effect of temperature on the thermodynamics of the complexation is discussed in terms of the electrostatic model and the change in the solvent structure.« less
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  • The thermodynamic parameters of complexation of Ln(III) cations with tris(2-aminoethyl)amine (tren) and tetraethylenepentamine (tetren) were determined in dimethyl sulfoxide (DMSO) by potentiometry and calorimetry. The excitation and emission spectra and luminescence decay constants of Eu 3+ and Tb 3+ complexed by tren and tetren, as well as those of the same lanthanides(III) complexed with diethylenetriamine (dien) and triethylenetetramine (trien), were also obtained in the same solvent. The combination of thermodynamic and spectroscopic data showed that, in the 1:1 complexes, all nitrogens of the ligands bound to the lanthanides except in the case of tren, in which only pendant N bound.more » For the larger ligands (trien, tren, tetren) in the higher complexes (ML 2), there was less complete binding by available donors, presumably due to steric crowding. FT-IR studies were carried out in an acetonitrile/DMSO mixture, suitably chosen in order to follow the changes in the primary solvation sphere of lanthanide(III) due to complexation of amine ligands. Results show that the mean number of molecules of DMSO removed from the inner coordination sphere of lanthanides(III) is lower than ligand denticity and that the coordination number of the metal ions increases with amine complexation from ~8 to ~10. Independently of the number and structure of the amines, linear trends, similar for all lanthanides, were obtained by plotting the values of ΔGj°, ΔHj° and TΔSj° for the complexation of ethylenediamine (en), dien, trien, tren and tetren as a function of the number of amine metal-coordinated nitrogen atoms. The main factors on which the thermodynamic functions of lanthanide(III) complexation reactions in DMSO depend are discussed.« less