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A family of new dinuclear lanthanide complexes as the simplest entities showing intramolecular magnetic interactions, [Ln2(dbm)2(L)2(CH3OH)2] (Ln = Tb (1), Dy (2), Ho (3), Er (4), Yb (5), Lu (6)), [Ln2(acac)2(L)2(EtOH)2] (Ln = Dy (7), Er (8)), [Dy2(TTA)2(L)2(CH3OH)2]·2CH2Cl2 (9) and [Dy2(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 β-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 (Ueff) 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 Ueff values of 9 and 10 have been improved. This proves that the β-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.

Six phenoxo-O bridged dinuclear lanthanide(iii) complexes have been assembled utilizing the 2-[(4-nitrophenyl)imino]methyl-8-hydroxyquinoline (HL) and dibenzoylmethane (Hdbm) ligands: [Ln2(dbm)4L2] (Ln = Nd (1), Eu (2), Gd (3), Tb (4), Dy (5) and Er (6)). Complexes 1 and 6 exhibit the characteristic emission peaks of the corresponding Nd3+ and Er3+ ions, respectively. Meanwhile, the excitation wavelength (470 nm) for complex 1 is located in the visible-light region, confirming a practical application value. The studies on magnetic properties reveal that complex 3 features a magnetocaloric effect with a magnetic entropy change of -ΔSm = 14.36 J kg-1 K-1 at 4 K for ΔH = 7 T. What's more, the dynamic magnetic studies for complex 5 show that it exhibits slow magnetic relaxation behavior, typical of SMM behavior, resulting in an energy barrier of ΔE/kB = 75 K with the pre-exponential factor τ0 = 2.2 × 10-7 s. Meanwhile, this research demonstrates that the magnetic properties can be modulated by regulating the electron-donating/withdrawing effects of the substituents on the ligands.