Synthesis, structure and property of two d-f heteronuclear Eu-TM (TM = Zn and Cd) complexes with open-chain ether Schiff base ligand

Abstract

Two heteronuclear Zn-Eu and Cd-Eu complexes with open-chain ether Schiff base ligand (bis(5-bromine-3-methoxysalicylidene)-3-oxapentane-1,5-diamine (H2L) and isonicotinate (IN), with composition [Zn2EuL2(OAc)(IN)](NO3)•(CH2Cl2) (1) and {[CdEuL(IN)(OAc)(NO3)(CH3OH)]•3(CH2Cl2)}n (2), have been synthesized and characterized. The structure analysis reveals that the Zn-Eu complex is heterotrinuclear cluster and lanthanide ion acts as a joint bridging of two Zn-L coordination units, whereas the Cd-Eu complex is infinite 1D zigzag coordination polymer formed by Cd-Eu-L secondary units through bridging of isonicotinate. Fluorescence properties of complexes 1–2 in the solid state and DMF solution at room temperature were studied. It has been found that the emission spectra of complexes 1–2 do not exhibit corresponding EuIII ion characteristic emission bands and the fluorescence properties of complexes 1–2 are different due to the introduction of different transition metal ions. Antioxidant properties of the ligand and complexes 1–2 were also studied, the results showed that the ligand and complexes 1–2 display high scavenging activity against hydroxyl (OH•) and superoxide (O2−•) radicals, and the order of the activity is complex 2 > complex 1 > H2L. Therefore, the structures and properties of d-f heteronuclear complexes can be adjusted by selecting different transition metal ions such as ZnII and CdII ions.