Crystallographic, X-ray absorption, and IR studies of solid- and solution-state structures of tris(nitrato) N,N,N ',N '-tetraethylmalonamide complexes of lanthanides. Comparison with the americium complex

To fine-tune the design of optimized donor ligands for nuclear waste actini de selective extraction, both electronic and molecular structures of the ac tinide complexes that are formed must be investigated. In particular, to ac hieve the selective complexation of transplutonium 3+ ions versus lanthanid e 3+ ions is one of the major challenges, given the chemical similarities b etween these two f-element families. In this work, the structure of solvent -phase M(NO3)(3)(TEMA)(2) complexes (Ln = Nd, Eu, Ho, Yb, Lu, Am; TEMA = N, N,N',N'-tetraethylmalonamide) was investigated by liquid-phase spectroscopi c methods among which extended X-ray absorption fine structure played a maj or role. In addition, the crystal structures of the species Nd(NO3)(3)(TEMA )(2) and Yb(NO3)(3)(TEMA)(2) have been determined by X-ray diffraction. Nd( NO3)(3)(C11N2O2H22)(2) crystallizes in the monoclinic system (P2(1) space g roup; a = 11.2627(4) Angstrom, b = 20.5992(8) Angstrom, c = 22.2126(8) Angs trom; alpha = gamma = 90 degrees, beta = 102.572(1)degrees; Z = 6), and Yb( NO3)(3)(C11N2O2H22)(2) crystallizes in the orthorhombic system (P2(1)2(1)2( 1) space group; a = 9.3542(1) Angstrom, b = = 18.1148(2) Angstrom, c = 19.7 675(2) Angstrom; alpha = beta = gamma = 90 degrees; Z = 4). In the solvent phase, the metal polyhedron was found to be similar to that of the solid-st ate complex Nd(NO3)(3)(TEMA)(2) for M = Nd to Ho. For M = Yb and Lu, a sign ificant elongation of one nitrate oxygen bond was observed. Comparison with measurements on the Am(NO3)(3)(TEMA)(2) complex in ethanol has shown the s imilarities between the Nd3+ and Am3+ coordination spheres.