BSTRACT In this research, we have designed and synthesized a new receptor, namely 4-((E)-(2,5-dichlorophenyl)diazenyl)-2-((E)-((4-hydroxyphenyl)imino)methyl)- phenol (L) for detection of hydrogen carbonate anions by naked-eye and UV–Vis spectroscopy. This compound revealed visual changes with HCO3 anion in aqueous media. No detectable color changes were observed upon the addition of any other tested anions. The sensitivity and selectivity of the receptor (L) to hydrogen carbonate anion was investigated by UV–Vis spectroscopy and 1H-NMR titration methods. The receptor (L) had a detection limit of 2.18 107 mol L1 toward HCO3 anions. Therefore, this compound was highly suitable for detection of hydrogen carbonate anion in aqueous solutions. The stability constant of the receptor (L)-HCO3 complex was determined by Benesi–Hildebrand plot method. The stoichiometry of this complex was determined (receptor (L)/anion ¼ 1:1) by Job’s plot technique. Overall, the designed chemosensor can be used for quick detection of hydrogen carbonate anions within the basic pH range
