Lanthanide Complexes with Multidentate Oxime Ligands as Single-Molecule Magnets and Atmospheric Carbon Dioxide Fixation Systems

Abstract

The synthesis, structure, and magnetic properties of five lanthanide complexes with multidentate oxime ligands are described. Complexes 1 and 2 (1: [La2 (pop)2 (acac)4 (CH3 OH)], 2: [Dy2 (pop)(acac)5 ]) are synthesized from the 2-hydroxyimino-N-[1-(2-pyridyl)ethylidene]propanohydrazone (Hpop) ligand, while 3, 4, and 5 (3: [Dy2 (naphthsaoH)2 (acac)4 H(OH)]⋅0.85 CH3 CN⋅1.58 H2 O; 4: [Tb2 (naphthsaoH)2 (acac)4 H(OH)]⋅0.52 CH3 CN⋅1.71 H2 O; 5: [La6 (CO3 )2 (naphthsao)5 (naphthsaoH)0.5 (acac)8 (CO3 )0.5 (CH3 OH)2.76 H5.5 (H2 O)1.24 ]⋅2.39 CH3 CN⋅0.12 H2 O) contain 1-(1-hydroxynaphthalen-2-yl)-ethanone oxime (naphthsaoH2 ). In 1-4, dinuclear [Ln2 ] complexes crystallize, whereas hexanuclear La(III) complex 5 is formed after fixation of atmospheric carbon dioxide. Dy(III) -based complexes 2 and 3 display single-molecule-magnet properties with energy barriers of 27 and 98 K, respectively. The presence of a broad and unsymmetrical relaxation mode observed in the ac susceptibility data for 3 suggest two different dynamics of the magnetization which might be a consequence of independent relaxation processes of the two different Dy(3+) ions.

Keywords: carbon dioxide fixation; crystal structures; lanthanides; magnetic properties; single-molecule magnets.