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All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Structural Trends and Vibrational Analysis of N,N,N′,N′−Tetramethylmalonamide Complexes Across the Lanthanide Series

Fundamental understanding of coordination chemistry across the lanthanide series is essential for explaining chemical behavior of rare-earth metals in complex liquid-liquid extraction processes, which in turn affects the distribution ratios and efficacy of separations as a whole. In this work, we explore the structural trends between the lanthanides and a neutral N,N,N',N'-tetramethylmalonamide (TMMA) ligand within four isolated families of solid-state compounds: Ln(trans-TMMA) 2 (NO 3 ) 3 Ln=La-Nd, Sm; Ln(cis-TMMA) 2 (NO 3 ) 3 Ln=Eu-Tb, Er; [Ln(TMMA) 3 (NO 3 ) 2 ][Ln(TMMA)(NO 3 ) 4 ] Ln=Dy-Tm; Ln(Κ 2 -TMMA)(iPrOH)(NO 3 ) 3 and Ln(Κ 1 -TMMA)(Κ 2 -TMMA)(NO 3 ) 3 Ln=Yb, Lu. Moving across the lanthanide series, we note the formation of both discrete charge-neutral complexes, as well as charged molecular anion-cation pairs, with variations in spatial ligand arrangement, coordination numbers, and ligand denticities. IR and Raman spectroscopy paired with DFT frequency calculations were used for an in-depth investigation of vibrational modes unique to each structural family. The collection of isolated model compounds was also discussed in the context of liquid-liquid separations based on reported distribution ratios from malonamide extraction.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Materials Data on Tb3Eu by Materials Project

Tb3Eu is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Tb is bonded to eight equivalent Tb and four equivalent Eu atoms to form TbTb8Eu4 cuboctahedra that share corners with twelve equivalent TbTb8Eu4 cuboctahedra, edges with eight equivalent EuTb12 cuboctahedra, edges with sixteen equivalent TbTb8Eu4 cuboctahedra, faces with four equivalent EuTb12 cuboctahedra, and faces with fourteen equivalent TbTb8Eu4 cuboctahedra. All Tb–Tb bond lengths are 3.59 Å. All Tb–Eu bond lengths are 3.59 Å. Eu is bonded to twelve equivalent Tb atoms to form EuTb12 cuboctahedra that share corners with twelve equivalent EuTb12 cuboctahedra, edges with twenty-four equivalent TbTb8Eu4 cuboctahedra, faces with six equivalent EuTb12 cuboctahedra, and faces with twelve equivalent TbTb8Eu4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TbEu3 by Materials Project

TbEu3 is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Tb is bonded to twelve equivalent Eu atoms to form TbEu12 cuboctahedra that share corners with six equivalent TbEu12 cuboctahedra, corners with twelve equivalent EuTb4Eu8 cuboctahedra, edges with eighteen equivalent EuTb4Eu8 cuboctahedra, faces with eight equivalent TbEu12 cuboctahedra, and faces with twelve equivalent EuTb4Eu8 cuboctahedra. There are six shorter (3.79 Å) and six longer (3.83 Å) Tb–Eu bond lengths. Eu is bonded to four equivalent Tb and eight equivalent Eu atoms to form EuTb4Eu8 cuboctahedra that share corners with four equivalent TbEu12 cuboctahedra, corners with fourteen equivalent EuTb4Eu8 cuboctahedra, edges with six equivalent TbEu12 cuboctahedra, edges with twelve equivalent EuTb4Eu8 cuboctahedra, faces with four equivalent TbEu12 cuboctahedra, and faces with sixteen equivalent EuTb4Eu8 cuboctahedra. There are a spread of Eu–Eu bond distances ranging from 3.76–3.91 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tb3Eu by Materials Project

Tb3Eu crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. there are two inequivalent Tb sites. In the first Tb site, Tb is bonded to eight Tb and four equivalent Eu atoms to form TbTb8Eu4 cuboctahedra that share corners with twelve equivalent TbTb8Eu4 cuboctahedra, edges with eight equivalent EuTb12 cuboctahedra, edges with sixteen TbTb8Eu4 cuboctahedra, faces with four equivalent EuTb12 cuboctahedra, and faces with fourteen TbTb8Eu4 cuboctahedra. There are four shorter (3.60 Å) and four longer (3.61 Å) Tb–Tb bond lengths. All Tb–Eu bond lengths are 3.61 Å. In the second Tb site, Tb is bonded to eight equivalent Tb and four equivalent Eu atoms to form TbTb8Eu4 cuboctahedra that share corners with four equivalent TbTb8Eu4 cuboctahedra, corners with eight equivalent EuTb12 cuboctahedra, edges with twenty-four TbTb8Eu4 cuboctahedra, faces with six equivalent EuTb12 cuboctahedra, and faces with twelve TbTb8Eu4 cuboctahedra. All Tb–Eu bond lengths are 3.60 Å. Eu is bonded to twelve Tb atoms to form EuTb12 cuboctahedra that share corners with four equivalent EuTb12 cuboctahedra, corners with eight equivalent TbTb8Eu4 cuboctahedra, edges with eight equivalent EuTb12 cuboctahedra, edges with sixteen equivalent TbTb8Eu4 cuboctahedra, faces with four equivalent EuTb12 cuboctahedra, and faces with fourteen TbTb8Eu4 cuboctahedra.

36 MATERIALS SCIENCE↗