A Sodium Sodate as Precursor for Lanthanide Bis(4- R -benzoxazol-2-yl)methanide Single-Molecule Magnets.

From the sodium sodate precursor [(Na(thf) 6 ][Na{(4-Me-NCOC 6 H 3 ) 2 CH} 2 ] ( 1 ) three isostructural dinuclear lanthanide complexes [(μ-Cl)Ln III {(4-MeNCOC 6 H 3 ) 2 CH} 2 ] 2 with Ln = Gd ( 2 ), Dy ( 3 ), and Er ( 4 ) based on the N , N' -chelating monoanionic bis(4-methylbenzoxazol-2-yl)methanide ligand (titled "Mebox") were synthesized and characterized by X-ray diffraction and magnetic measurements. The sodium precursor 1 was analyzed via X-ray diffraction and diffusion-ordered NMR spectroscopy experiments (DOSY-NMR) in order to investigate its aggregation in solution and the solid state. The sodium analog [(thf) 3 Na(NCOC 6 H 4 ) 2 CH] ( 1 ') based on the bis(benzoxazol-2-yl)-methanide ligand (titled "box") was prepared and analyzed for comparison reasons. From the lanthanide derivatives 2 - 4 , the Dy III complex 3 displays slow relaxation of magnetization at zero field, with a relaxation barrier of U = 315.7 cm -1 . The coupling strength between the two lanthanide centers was estimated with the Gd III equivalent 2 , giving a weak antiferromagnetic coupling of J = -0.035 cm -1 .