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

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)center dot(CH2Cl2) (1) and ([CdEuL(IN)(OAc)(NO3)(CH3OH)]center dot 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 Eu-III 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 center dot) and superoxide (O-2(-)center dot) 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 Zn-II and Cd-II ions. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

Two heteronuclear Zn-Eu and Cd-Eu complexes with distinct structures and fluorescence properties were synthesized and characterized. The complexes exhibited high scavenging activity against hydroxyl and superoxide radicals, with complex 2 showing the highest activity.