- Thermodynamic, Spectroscopic, and Computational Studies of f-Element Complexation by N-Hydroxyethyl-diethylenetriamine-N,N′,N,N-tetraacetic Acid
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Potentiometric and spectroscopic techniques were combined with DFT calculations to probe the coordination environment and determine thermodynamic features of trivalent f-element complexation by N-hydroxyethyl-diethylenetriamine-N,N′,N,N-tetraacetic acid, HEDTTA. Ligand protonation constants and lanthanide stability constants were determined using potentiometry. Five protonation constants were accessible in I = 2.0 M (H+/Na+)ClO4. UV-vis spectroscopy was used to determine stability constants for Nd3+ and Am3+ complexation with HEDTTA. Luminescence spectroscopy indicates two water molecules in the inner coordination sphere of the Eu/HEDTTA complex, suggesting HEDTTA is heptadentate. Luminescence data was supported by DFT calculations, which demonstrate that substitution of the acetate pendant arm by a N-hydroxyethyl group weakens the metal-nitrogen bond. This bond elongation is reflected in HEDTTA’s ability to differentiate trivalent actinides from trivalent lanthanides. The trans-lanthanide Ln/HEDTTA complex stability trend is analogous to Ln/DTPA complexation; however, the loss of one chelate ring resulting from structural substitution weakens the complexation by ～3 orders of magnitude. Successful separation of trivalent americium from trivalent lanthanides was demonstrated when HEDTTA was utilized as aqueous holdback complexant in a liquid-liquid system. Time-dependent extraction studies for HEDTTA were compared to diethylenetriamine-N,N,N′,N,N-pentaacetic acid (DTPA) and N-hydroxyethyl-ethylenediamine-N,N′,N′-triacetic acid (HEDTA). The results indicate substantially enhanced phase-transfer kinetic rates for mixtures containing HEDTTA.
- Grimes, Travis S.,Heathman, Colt R.,Jansone-Popova, Santa,Bryantsev, Vyacheslav S.,Goverapet Srinivasan, Sriram,Nakase, Masahiko,Zalupski, Peter R.
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- PROCESS FOR MANUFACTURING CHAIN-EXTENDED HYDROXYETHYLETHYLENEAMINES, ETHYLENEAMINES, OR MIXTURES THEREOF
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The invention pertains to a process for preparing hydroxyethylethyleneamines, ethyleneamines, or mixtures thereof, and/or ethylene urea derivatives thereof comprising the step of reacting diethanolamine with an amine-functional compound comprising at least two –NH-units of which at least one is selected from the group of primary amine groups and cyclic secondary amine groups, the amine-functional compound comprising at least one –NH-CH2-CH2-NH-unit wherein one or more -NH- CH2-CH2-NH-units in the amine-functional compound may be present in the form of cyclic ethylene urea moieties, piperazine moieties, or linear ethylene urea moieties, in the presence of a carbon oxide delivering agent, wherein -the molar ratio of amine-functional compound to diethanolamine is at least 0.2:1, and -the molar ratio of carbon oxide delivering agent to –NH-CH2-CH2-NH-units in the amine-functional compound is at least 0.1:1. The invention makes it possible to obtain higher hydroxyethylethyleneamines, ethyleneamines, or mixtures thereof, and/or ethylene urea derivatives thereof from diethanolamine, which is an attractive starting material.
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Page/Page column 16; 17; 18
(2018/10/24)
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