Slow Relaxation Processes and Single-Ion Magnetic Behaviors in Dysprosium-Containing Complexes

A series of one-dimensional complexes [Ln(L-1)(3)(HOCH2CH2OH)](n) (L-1 = 2-furoate anion; Ln = Nd (1), Sm (2), Gd (3), Tb (4), Dy (5), Er (6)) have been synthesized. The complexes were crystallized in the monoclinic space group P2(1)/c and show a chain-like structure determined by single-crystal X-ray diffraction. Magnetic properties indicate that carboxyl group of 2-furoate mediates different magnetic couplings in light and heavy rare earth complexes, namely, antiferromagnetic interaction between light rare earth ions and ferromagnetic interaction between heavy ones. Noticeably, complex 5 displays a strong frequency dependence of alternating current (AC) magnetic properties. Further magnetic studies show a distribution of a single relaxation process in 5. While 1,10-phenanthroline and phthalate anion (L-2) were employed, [Dy-2(L-2)(6)(H2O)](n) (7) was isolated by hydrothermal reactions and characterized magnetically. Research results also show the frequency dependence of AC magnetic susceptibilities, although the phthalate anions mediate antiferromagnetic coupling between Dy-III ions. Further magnetic investigation of a neutral mononuclear complex with the formula [Dy(TTA)(3)(L-3)] (8) (TTA = 2-thenoyltrifluoroacetonate; L-3 = 4,5-pinene bipyridine) suggests that the single-ion magnetic behavior originates the slow relaxation of Dy-III-containing complexes.