New Chromenylium−cyanine based dual channel chemosensors for copper and hypochlorite sensing

Abstract

Based on a change in optical properties of chromenylium−cyanine Schiff base derivatives (5a-c), a series of colorimetric dual sensors have been for the first time designed, synthesized and characterized to monitor Cu2+ and OCl− ions at near-IR (NIR) region in aqueous samples. The colorimetric responses of the sensors toward Cu2+ and OCl− ions were evaluated for aqueous samples within a series of the competitive anions and cations at pH 7.2. The sensors detected Cu2+ selectively via Cu2+-promoted spirocyclic ring–opening reaction while photophysical change during OCl− recognition is due to the spirocyclic ring−opening reaction by coordination Cu2+ ion generated from reaction between Cu+ and hypochlorite ions in analysis media. Mass and IR data suggest a 1:1 complex formation between Cu2+ and the receptor via phenolic O atom, N atom from Schiff base and O atom from spirocycle form. The detection limits of the dual sensors (5a-c) were determined to be 3.3 × 10−8 M, 1.93 × 10−8 M and 2.36 × 10−8 for Cu2+ determination and 2.83 × 10−8 M, 2.10 × 10−8 M and 2.60 × 10−8 M for OCl− determination, indicating a high sensitivity of the sensors for Cu2+ and OCl− detection Additionally, we present the first single-crystal structure analysis of a chromenylium-cyanine Schiff base in this study.