Sensitive colorimetric detection of CN− and AcO− anions in a semi-aqueous environment through a coumarin–naphthalene conjugate azo dye

Abstract

In the present study, we described the design and synthesis of an azo auxochrome containing a 2-aminothiazolyl coumarin and naphthalene conjugate as a molecular probe 5. Upon interaction with anions, the probe 5 displayed a naked-eye sensitive colorimetric response towards the detection of cyanide (CN⁻) and acetate (AcO⁻) anions in a 50% aqueous–ethanol (EtOH : H₂O; v/v, 1 : 1) solution. The limits of detection for the cyanide and acetate anions were found to be 0.756 and 0.916 μM, respectively. The mechanism of interaction between the probe and both the anions has been confirmed by different spectroscopic data. The ¹H NMR, ¹³C NMR, FTIR and HRMS data clearly confirmed the deprotonation of probe 5 in the presence of both anions. Moreover, the molecular probe 5 has shown good compatibility for the detection of CN⁻ and AcO⁻ anions on test paper strips.