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 U_eff = 84 K and the preexponential factor τ₀ = 5.1 × 10^–9 s.