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

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 Cu 2+ . Addition of Cu 2+ 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 Cu 2+ in a 1:1 stoichiometry and their association constant is determined as 3.2   ×   10 4   L   mol −1 . Experimental results indicate that the BMSRH can provide a rapid, selective and sensitive response to Cu 2+ with a linear dynamic range 0.667–240   μmol/L. Common interferent ions do not show any interference on the Cu 2+ determination. It is anticipated that BMSRH can be a good candidate probe and has potential application for Cu 2+ determination. The proposed probe exhibits the following advantages: a quick, simple and facile synthesis.