ABSTRACT In the present study, a novel colorimetric Schiff-base receptor 4-((2-nitrophenyl) diazenyl)-2-((3-methylpyridin-2-ylimino)methyl)phenol was successfully synthesized via the condensation reaction of an azo-coupled precursor to 2-amino-3-methylpyridine in absolute ethanol and a good yield. The probe provided the selective detection of trivalent Cr3þ, Fe3þ, and Al3þ cations with different color changes. The binding constants of complexation (ka), the molar absorption coefficient (E), and the limit of detection parameters of trivalent ions were measured for Cr3þ, Fe3þ, and Al3þ. The results revealed a high sensitivity for the selective detection of Fe3þ ions. Moreover, the devised receptor rapidly detected the HSO4 anion through absorption spectra and color changes. The HSO4 and Al3þ coordination properties were checked by the 1HNMR titration method. The sensing behavior of the L receptor was further emphasized in computational studies. Accordingly, quantum-chemical studies via Density Functional Theory (DFT) were carried out using the 6–31þG (d) basis set of the Gaussian 03 program package in order to more supplement the detecting behavior of the L receptor in case of HSO4 anions. The HSO4 and Al3þ coordination properties were investigated by the 1HNMR titration.
