title: Solid-state and solution-state coordination chemistry of lanthanide(III) complexes with α-hydroxyisobutyric acid.
abstract: Despite the wide range of applications of α-hydroxyisobutyric acid (HIBA) in biochemical processes, pharmaceutical formulations, and group and elemental separations of lanthanides and actinides, the structures and geometries of lanthanide-HIBA complexes are still not well understood. We reacted HIBA with lanthanides in aqueous solution at pH = 5 and synthesized 14 lanthanide-HIBA complexes of the formula [Ln(HIBA)(2)(H(2)O)(2)](NO(3))·H(2)O (Ln = La (1), Ce (2), Pr (3), Nd (4), Sm (5), Eu (6), Gd (7), Tb (8), Dy (9), Ho (10), Er (11), Tm (12), Yb (13), Lu (14)), isolating single crystals (1-7, 10, and 11) and powders (8, 9, and 12-14). Both single-crystal and powder X-ray diffraction studies reveal a two-dimensional extended structure across the entire lanthanide series. The environment around the eight-coordinated Ln(III) atom is best described as a distorted dodecahedron, where HIBA acts as a monoanionic tridentate ligand with one carboxylato oxygen atom and one hydroxyl oxygen atom chelating to one Ln(III) center. The carboxylato oxygen atom from a second HIBA ligand bridges to a neighboring Ln(III) atom to form a two-dimensional extended structure. While the coordination mode for HIBA is identical across the lanthanide series, three different structure types are found for La, Ce-Ho, and Er-Lu. Solution characterization using (13)C NMR further confirmed a single solution complex under the crystallization conditions. Raman and UV-vis-NIR absorbance and diffuse reflectance spectra of HIBA-Ln(III) complexes were also measured.
authors.affiliation: Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States.
authors.forename: Xiao-Yan
authors.initials: XY
authors.lastname: Chen
authors.forename: George S
authors.initials: GS
authors.lastname: Goff
authors.forename: William C
authors.initials: WC
authors.lastname: Ewing
authors.forename: Brian L
authors.initials: BL
authors.lastname: Scott
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Runde
mesh_terms: D056831:Coordination Complexes / Q000138:chemical synthesis / Q000737:chemistry*; D018360:Crystallography, X-Ray; D006863:Hydrogen-Ion Concentration; D006885:Hydroxybutyrates / Q000737:chemistry*; D028581:Lanthanoid Series Elements / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D012996:Solutions; D014867:Water / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D056831:Coordination Complexes; D006885:Hydroxybutyrates; D028581:Lanthanoid Series Elements; D012996:Solutions; D014867:Water; C008039:2-hydroxyisobutyric acid