Crystal structure, fluorescence, magnetic properties and DNA interaction of four novel binuclear LnⅢ2 compounds with Schiff ligand

Abstract

Four new Ln2 compounds, [Ln2(H2L−)2(acac)2(CH3O)2] (Ln = Sm(1), Tb(2), Ho(3) and Er(4), H3L = 2‑hydroxy-N’-[(1E)-(8-hydroxyquinolin-2-yl)methylidene]benzohydrazide), were synthesized by using a multidentate Schiff ligand and lanthanide β-diketone salts via solvent evaporation methods. The X-ray structural analysis reveal that the four Ln2 compounds are dinuclear compounds and each Ln(Ⅲ) ion is eight-coordinated. The two central Ln(Ⅲ) ions are bridged by two μ2O atoms from 8-hydroxyquinoline Schiff base ligands, leading to a parallelogram Ln2O2 core. The magnetism investigation shows that compound 2 display slow magnetic relaxation behavior under zero dc field (ΔE/kB = 19.77 K and τ0 = 1.35 × 10−6 s). Subsequent studies strongly suggested that the four Ln2 compounds binded to Calf thymus DNA (CT-DNA) through intercalative mode and have pBR322 plasmid DNA cleavage ability. This work will provide more insights for the design and investigation of lanthanide-based SMMs, and has certain reference value to study the interaction between compound and DNA.