New Chloro-Based Azo-Azomethine Dyes: Synthesis, Biological and Optical Spectroscopic Studies for Detection of some Transition Metal Ions

Two new chromogenic receptors 1,2-[1-(3-imino-4-hydroxophenylazobenzene)]-4-chlorobenzene (1a) and 1,2-[1-(3-imino-4-hydroxophenylazo-4-nitrobenzene)]-4-chlorobenzene (1b) have been designed and chearcterized for detection of some transition metal ions in DMSO solution by UV/Vis spectroscopy. Upon addition of Cd2+, Zn2+ and Cu2+ ions to 1a in DMSO, the peak at 460 nm increases in intensity, while the band at 352 nm decreases in intensity and approximately disappears. n ->pi* transition of azo groups of 1a decreases in intensity after adding Hg2+ ions and does not change after adding Ni2+ ions. This indicates high tendency of 1a towards Cd2+, Zn2+ and Cu2+ against Ni2+ and Hg2+ ions. Compound 1b shows some color changes after addition of metal ions. Upon addition of all metal ions to 1b in DMSO, the band at 560 nm increases in intensity with the hypsochromic shift for Cu2+, Zn2+, Co2+ and Ni2+. But the largest blue shift (-67 nm) is seen after adding Cu2+ ion with remarkable color change from violet-green to orange. Benesi-Hildebrand plot and Jobs method are used for determination of binding constant (K-a) and stoichiometry of formed complexes with 1b. Then, complex Cu(II) with 1b is synthezied for recognition of binding sites of ligand. The results indicate that 1b behaves as one tetradentate ligand with N and O donor atoms when bound to Cu(II). Moreover, the study of antioxidant properties of 1a and 1b with DPPH method reveals good and significant activity.