Mononuclear and Tetranuclear Compounds of Yttrium and Dysprosium Ligated by a Salicylic Schiff-Base Derivative: Synthesis, Photoluminescence, and Magnetism

The Schiff-base (2-aminoethyl)­hydroxybenzoic
acid (H2L) as a proligand was prepared in situ from 3-formylsalicylic
acid
and ethanolamine (ETA). The mononuclear {[Y­(HL)4]­[ETAH]·H2O} (1) and {[Dy­(HL)4] [ETAH]·3MeOH·H2O} (2) and tetranuclear {[Y4(HL)2(L)4(μ3-OH)2]·4MeOH·4H2O} (3), {[Dy4(HL)2(L)4(μ3-OH)2]·5­(MeOH)2·7H2O (4), and {[Dy4(HL)8(L)2]·4MeOH·2H2O}­(5) rare-earth metal complexes of this ligand could be obtained as
single-crystalline materials by the treatment of H2L in
the presence of the metal salts [Ln­(NO3)3·(H2O)m] (Ln = Y, Dy). In the solid
state, the tetranuclear compounds 3 and 4 exhibit butterfly structures, whereas 5 adopts a rectangular
arrangement. Electrospray ionization mass spectrometry data of the
ionic compounds 1 and 2 support single-crystal
X-ray analysis. The yttrium compounds 1 and 3 show fluorescence with 11.5% and 13% quantum yield, respectively,
whereas the quantum yield of the dysprosium complex 4 is low. Magnetic studies on the dysprosium compounds 4 and 5 suggest the presence of weak antiferromagnetic
interactions between neighboring metal centers. Compound 4 shows single-molecule-magnet behavior with two relaxation processes,
one with the effective energy barrier Ueff = 84 K and the preexponential factor τ0 = 5.1 ×
10–9 s.