Fabrication of a lanthanide complex with specific magnetic and optical properties

Aiming at control of molecular structure of lanthanide complexes, generally difficult owing to the large coordination number and also to the complexity coming from variation in ionic radius called lanthanide contraction, the authors synthesized a series of the rare earth (from La to Yb) complexes having a redox-active ligand, [Ln(aminoquinone)2(Otf)3] where Otf=CF3SO3-, and investigated the change in magnetic and optical properties with varying central metals. Neutral complexes were prepared by designing the ligand coordinating to metal through three atoms, 2,3-diaminonaphthoquinone neutralized by triethylamine in acetonitrile, further treated with La trifluoromethane-sulfonate. The structure was confirmed by X-ray crystallography with bond length estimated. Coordination structural change with changing central metal was studied in view of ionic radius of metal. One-electron reduction of the ligand was studied with Ln=La, Ga, and Yb, the interaction of the resulting organic radical with f-electron of the metal studied by ESR. Magnetic susceptibility was measured as function of temperature and discussed from the molecular structural view point. (S. Ohno)