A novel colorimetric chemosensor for multiple target metal ions Fe2+, Co2+, and Cu2+ in a near-perfect aqueous solution: Experimental and theoretical studies

- A multifunctionalchemosensor 1 for Fe2+, Co2+ and Cu2+ was developed.
- Sensor 1 could simultaneously detect Fe2+, Co2+ and Cu2+ by color change.
- Detection limits for Fe (II) and Co (II) were the lowest among those reported by naked eye.
- Sensing mechanisms of Co2+ and Cu2+ by 1 were supported by theoretical calculations.

A selective and multifunctional chemosensor 1 for Fe2+, Co2+ and Cu2+ was designed and synthesized. 1 could simultaneously detect Fe2+, Co2+ and Cu2+ by changing its color from colorless to pink (Fe2+) and to yellow (Co2+ and Cu2+), respectively, in a near-perfect aqueous solution. The binding modes of 1 to Fe2+, Co2+ and Cu2+ were determined to be a 1:1, 2:1, and 1:1, respectively, through Job plot and ESI-mass spectrometry analysis. The detection limits (0.43 μM, 0.11 μM and 0.28 μM) of 1 for Fe2+, Co2+ and Cu2+ were much lower than the US Environmental Protection Agency (EPA) guidelines (5.36 μM for Fe2+ and 1.7 μM for Co2+) and the WHO guideline (31.5 μM for Cu2+) for the drinking water. Moreover, the chemosensor 1 could be used to quantify Fe2+, Co2+ and Cu2+ in water samples, and applied to test kits for detecting Fe2+, Co2+ and Cu2+. The sensing mechanisms of Co2+ and Cu2+ by 1 were supported by theoretical calculations.

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