A selectively rhodamine-based colorimetric probe for detecting copper(II) ion

• A novel rhodamine B derivative 3-bromo-5-methylsalicylaldehyde rhodamine B hydrazone (BMSRH) was synthesized and characterized.
• BMSRH have a rapid, selective and sensitive response to Cu2+.
• The response of BMSRH to Cu2+ is reversible .
• BMSRH can be a good colorimetric probe for Cu2+ determination.

A novel rhodamine derivative 3-bromo-5-methylsalicylaldehyde rhodamine B hydrazone (BMSRH) has been synthesized by reacting rhodamine B hydrazide with 3-bromo-5-methylsalicylaldehyde and developed as a new colorimetric probe for the selective and sensitive detection of Cu2+. Addition of Cu2+ to the solution of BMSRH results in a rapid color change from colorless to red together with an obvious new band appeared at 552 nm in the UV–vis absorption spectra. This change is attributed to the spirocycle form of BMSRH opened via coordination with Cu2+ in a 1:1 stoichiometry and their association constant is determined as 3.2 × 104 L mol−1. Experimental results indicate that the BMSRH can provide a rapid, selective and sensitive response to Cu2+ with a linear dynamic range 0.667–240 μmol/L. Common interferent ions do not show any interference on the Cu2+ determination. It is anticipated that BMSRH can be a good candidate probe and has potential application for Cu2+ determination. The proposed probe exhibits the following advantages: a quick, simple and facile synthesis.

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