One new azo Schiff-base derivative: 4-bromo-1,2-bis[2-hydroxy-5-(phenylazo)benzylideneamino]benzene (H2L) was synthesized and characterized by common spectroscopic techniques and elemental analysis. The ability of the new chemosensor for detection of some main and transition metal ions was studied by UV-Vis spectroscopy in the mixture of DMSO: water (9:1). Upon addition of Ca2 and Cd2 ions, dramatic changes were observed in the UV-Vis spectrum of ligand (one new absorbance band appeared in the range of 430- 450 nm, while the absorbance band at 351 nm disappeared). The stoichiometry of the complexes was determined using the Job method. The binding constants of Ca2 and Cd2 with receptor by Benesi-Hildebrand plots were found to be 2.874×104 M-1 and 6.445×104 M-1, respectively. The results indicated the receptor can recognize Ca2 and Cd2 ions from other cations in aqueous solution. Finally, the structure and electronic properties of the ligand and its complexes with Ca2 and Cd2 ions were analyzed by DFT and TD-DFT calculations.
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