Mononuclear Dy(III)/heteropolynuclear Zn(II)–Dy(III) Schiff base complexes: Synthesis, structures, fluorescence and antioxidant properties

Abstract

Three new open-chain ether Schiff base complexes, formulated as [DyH2L(NO3)3]·(CH3CN) (1), [ZnDyL(NO3)2(OAc)(CH3OH)]·(CH3OH)3 (2) and [Zn2DyL2(OAc)(nicotinate)](NO3)(3) (H2L = bis(5-bromine-3-methoxysalicylidene) -3-oxapentane-1,5-diamine), have been synthesized by interfacial diffusion methods. Structural analysis shows that complex 1 is a mononuclear Dy(III) complex, each Dy(III) ion was chelated by the outer O2O2 of the Schiff base ligand H2L. In d–f heterobinuclear complex 2, Zn(II) and Dy(III) were encapsulated in the inner and outer cavities of the deprotonated ligand L2−, respectively. In d–f heterotrinuclear complex 3, Zn(II) ions and deprotonated L2− form ZnL units and were bridged by a Dy(III) ion. Fluorescence properties of 1–3 in the solid state were studied. In comparison with the free H2L ligand, the fluorescence peaks of the three Schiff base complexes were significantly blue shifted and enhanced. It is attributed to the coordination of ligand with metal ions. The results of antioxidant experiments in vitro showed that H2L and complexes 1–3 possess favorable activities in scavenging hydroxyl radicals as well as superoxide radicals, and all complexes exhibited better scavenging activities than free H2L.