Design and synthesis of new chemosensors for metal ions has received considerable attention because they play important roles in living systemsand have an extremely toxic impact on the environment [1]. In recent years, many efforts have been devoted to design of various chemosensors specific for Ni 2+ ion detection [2]. The most attractive approach focuses on the research of novel colorimetric Ni 2+ ion sensors, which allow naked eyes detection of the change of color without resorting to the use of expensive instruments [3]. In the present work, we have explored a new derivative of azo-azomethine with N donors set of atoms that demonstrating excellent selectivity towards Ni 2+ ion. The azo-azomethine ligand has been synthesized via condensation reaction of 1,2-bis(2-aminophenylthio)ethane with 5-(4chloro-phenyl)-azo-salicylaldehyde.The new prepared sensor was were characterized by IR, H NMR,mass spectrometry and elemental analysis. The proposed sensor shows a reasonable discrimination ability towards Ni 2+ ion in comparison to some alkali, alkaline earth, transition and heavy metal ions via dramatic color change from pale yellow to orange which can easily be observed by the naked eye. To investigate the selectivity of receptor, the UV–Vis absorption spectral behavior upon the addition of metal ion was monitored (Fig.1).
