Complexation of Lanthanides with Nitrate at Variable Temperatures: Thermodynamics and Coordination Modes
Authors:
- 30 December 2008
- journal article
- research article
- Published by American Chemical Society (ACS) in Inorganic Chemistry
- Vol. 48 (3) , 964-970
Abstract
Complexation of neodymium(III) with nitrate was studied at variable temperatures (25, 40, 55, and 70 °C) by spectrophotometry and microcalorimetry. The NdNO32+ complex is weak and becomes slightly stronger as the temperature is increased. The enthalpy of complexation at 25 °C was determined by microcalorimetry to be small and positive, 1.5 ± 0.2 kJ·mol−1, in good agreement with the trend of the stability constant at variable temperatures. Luminescence emission spectra and the lifetime of Eu(III) in nitrate solutions suggest that inner-sphere and bidentate complexes form between trivalent lanthanides (Nd3+ and Eu3+) and nitrate in aqueous solutions. A specific ion interaction approach was used to obtain the stability constants of NdNO32+ at infinite dilution and variable temperatures.Keywords
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