Slow magnetic relaxations in a ladder-type Dy(iii) complex and its dinuclear analogue

The complex {[Dy₂(PDOA)₃(H₂O)₆]·2H₂O}_n (1) (H₂PDOA = 1,2-phenylenedioxydiacetic acid) was prepared from aqueous solution. Its crystal structure, built up of {-Dy-O-C-O-}_n chains interlinked by PDOA ligands yielding a ladder-like arrangement, was determined at 173 K. 1 exhibits slow magnetic relaxation under a small magnetic field B_DC = 0.2 T with two (LF and HF) relaxation channels. The LF relaxation time at B_DC = 0.2 T and T = 1.85 K is as slow as τ(LF) = 46 ms whereas the HF channel is τ(HF) = 1.4 ms. The mole fraction of the LF species is x_LF = 0.76 at 1.85 K and it escapes progressively on heating. In the dinuclear analogue [Dy₂(PDOA)₃(H₂O)₆]·3.5H₂O (2) one PDOA ligand forms a bis(chelate) bridge between the two Dy(iii) atoms yielding a local structure analogous to that in 1; however its AC susceptibility data show slightly different quantitative characteristics of the single-molecule magnetic behaviour.