Luminescent Single-Ion Magnets from Lanthanoid(III) Complexes with Monodentate Ketone Ligands

摘要

We synthesized [Ln~(III)(hfac)3(H_20)(L)] (abbreviated as Ln-L; Ln= Gd, Tb, Eu; L= DTBK (di-t-butyl ketone), BP (benzophenone)), in which the carbonyl oxygen atom was coordinated to the Ln ion center, despite of such bulky substituents. Their crystal structures were determined by means of X-ray diffraction study. Gd-DTBK is completely isomorphous to the di-t-butyl nitroxide derivative and accordingly can be regarded as a model with the ligand spin masked. The ac magnetic susceptibility measurements on Tb-DTBK and -BP showed frequency dependence, characteristic of single-ion magnets. They also displayed photoluminescence in the solid state at room temperature. The quantum yields of the luminescence of Tb-DTBK and -BP (λ_(ex)= 360 nm) were improved to 57 and 35%, respectively, from that of the starting material [Tb~(III)(hfac)_3(H_20)_2] (28% at λ_(ex)= 370 nm). Similarly, the quantum yields for Eu-DTBK and -BP were 8 and 15%, respectively, with λ_(ex)= 400 nm, while that of the starting material [Eu~(III)(hfac)_3(H_2O)_2] was 4% at λ_(ex)= 400 nm.