A novel colorimetric chemosensor for detection of Co²⁺ and S²⁻ in an aqueous environment

A novel multifunctional and highly selective chemosensor 1, N 2-(bis(pyridin-2-ylmethyl)amino)-N-(2-((2,4-dinitrophenyl)amino)phenyl)acetamide, for Co²⁺and S²⁻was designed and synthesized. Sensor 1 showed a selective colorimetric sensing ability for cobalt ion by changing color from pale yellow to light green in a near perfect aqueous solution. The detection limit (0.99 μM) of 1 for Co²⁺was lower than the Environmental Protection Agency (EPA) guideline (1.7 μM) for drinking water. The sensor 1 could be used to quantify Co²⁺in water samples. Moreover, sensor 1 detected S²⁻selectively, which induced an obvious color change from pale yellow to pink over most other competitive anions in aqueous solution. The sensing mechanism of Co²⁺by 1 was proposed to be a ligand-to-metal charge-transfer (LMCT) with the experimental results and theoretical calculations, and that of S²⁻by 1 proposed to be a deprotonation process. Therefore, this sensor 1 could be used as a practical system for monitoring both Co²⁺and S²⁻in an aqueous environment.