TY - JOUR

T1 - Complexation of Am (III) and Nd (III) by 1, 10-phenanthroline-2, 9-dicarboxylic acid

AU - Ogden, Mark

AU - Sinkov, Serguei I.

AU - Nilson, Mikael

AU - Lumetta, Gregg J.

AU - Hancock, Robert D.

AU - Nash, Kenneth L.

PY - 2013/1/1

Y1 - 2013/1/1

N2 - The complexant 1,10-phenanthroline-2,9-dicarboxylic acid (PDA) is a planar tetradentate ligand that is more preorganized for metal complexation than its unconstrained analogue ethylendiiminodiacetic acid (EDDA). Furthermore, the backbone nitrogen atoms of PDA are aromatic, hence are softer than the aliphatic amines of EDDA. It has been hypothesized that PDA will selectively bond to trivalent actinides over lanthanides. In this report, the results of spectrophotometric studies of the complexation of Nd(III) and Am(III) by PDA are reported. Because the complexes are moderately stable, it was necessary to conduct these titrations using competitive equilibrium methods, competitive cation complexing between PDA and diethylenetriaminepentaacetic acid, and competition between ligand protonation and complex formation. Stability constants and ligand protonation constants were determined at 0.1 mol·L−1 ionic strength and at 0.5 mol·L−1 ionic strength nitrate media at 21 ± 1 °C. The stability constants are lower than those predicted from first principles and speciation calculations indicate that Am3+ selectivity over Nd3+ is less than that exhibited by 1,10-phenanthroline.

AB - The complexant 1,10-phenanthroline-2,9-dicarboxylic acid (PDA) is a planar tetradentate ligand that is more preorganized for metal complexation than its unconstrained analogue ethylendiiminodiacetic acid (EDDA). Furthermore, the backbone nitrogen atoms of PDA are aromatic, hence are softer than the aliphatic amines of EDDA. It has been hypothesized that PDA will selectively bond to trivalent actinides over lanthanides. In this report, the results of spectrophotometric studies of the complexation of Nd(III) and Am(III) by PDA are reported. Because the complexes are moderately stable, it was necessary to conduct these titrations using competitive equilibrium methods, competitive cation complexing between PDA and diethylenetriaminepentaacetic acid, and competition between ligand protonation and complex formation. Stability constants and ligand protonation constants were determined at 0.1 mol·L−1 ionic strength and at 0.5 mol·L−1 ionic strength nitrate media at 21 ± 1 °C. The stability constants are lower than those predicted from first principles and speciation calculations indicate that Am3+ selectivity over Nd3+ is less than that exhibited by 1,10-phenanthroline.

KW - americium

KW - neodymium

KW - stability constant

KW - complexation

KW - speciation

KW - actinide chemistry

U2 - 10.1007/s10953-012-9940-2

DO - 10.1007/s10953-012-9940-2

M3 - Article

VL - 42

SP - 211

EP - 225

JO - Journal of Solution Chemistry

JF - Journal of Solution Chemistry

SN - 1572-8927

ER -