Modulation of the properties of dinuclear lanthanide complexes through utilizing different beta-diketonate co-ligands: near-infrared luminescence and magnetization dynamics

摘要

A family of new dinuclear lanthanide complexes as the simplest entities showing intramolecular magnetic interactions, [Ln(2)(dbm)(2)(L)(2)(CH3OH)(2)] (Ln = Tb (1), Dy (2), Ho (3), Er (4), Yb (5), Lu (6)), [Ln(2)(acac)(2)(L)(2)(EtOH)(2)] (Ln = Dy (7), Er (8)), [Dy-2(TTA)(2)(L)(2)(CH3OH)(2)]center dot 2CH(2)Cl(2) (9) and [Dy-2(tfa)(2)(L)(2)(CH3OH)(2)] (10) (H2L = N '-(2-hydroxy-5-methylphenyl)-pyrazine-2-carbohydrazide, Hdbm = 1,3-diphenyl-1,3-propanedione, Hacac = acetylacetone, HTTA = 2-thenoyltrifluoroacetone, Htfa = trifluoroacetylacetone), were constructed successfully by the reaction of a Schiff base ligand H2L and four different beta-diketonate salts. As for complexes 4, 5 and 8, all exhibit the characteristic emission peaks of the corresponding Er3+, Yb3+ and Er3+ ions, respectively. Meanwhile, the excitation wavelength (510 nm) of 5 is located in the visible region, confirming its significant potential application value. Magnetic studies indicate that complexes 9 and 10 exhibit characteristic slow relaxation of magnetization with the energy barriers (U-eff) of 102 K for 9 and 140 K for 10 under a zero dc field. Under the optimized dc fields, slow magnetic relaxations are present in 2 and 7, and the U-eff values of 9 and 10 have been improved. This proves that the beta-diketonate co-ligands deserve an important role in regulating Dy-SMMs influenced by the diverse perturbations of the axial crystal field originating from minor changes in the coordination environment.