Spectroscopic properties of some new azo-azomethine ligands in the presence of Cu2+, Pb2+, He2+, Co2+, Ni2+, Cd2+ and Zn2+ and their antioxidant activity

Due to their potential applicability as selective receptors in optical sensors, two novel azo Schiff-base derivatives I and II are synthesized and characterized with FT-IR, H-1 NMR and elemental analysis techniques. The optical response of azo groups of I and II towards Ni2+, Co2+, Cu2+, Pb2+, Hg2+, Zn2+ and Cd2+ metal ions is studied in DMSO by UV-vis spectroscopy. The absorption spectra of both compounds with cations show marked changes. In solution, azo Schiff-base I produces a cation induced 95 nm blue shift for Cu2+ ion from 555 nm to 460 nm with remarkable color change from red to yellow. Whereas no significant color change is observed upon addition of studied metal cations to the solution of ligand II or other metal ions to the solution of ligand I. Furthermore, Job's plot indicate 1:1 binding-stoichiometry for I with Cu2+ ion and Benesi-Hildebrand plot is used for the determination of its association constant. Therefore receptor I is highly specific for copper ions in DMSO solution. Finally, the study of antioxidant properties of I and II with DPPH method reveals high and significant activities. (C) 2014 Elsevier B.V. All rights reserved.