Simultaneous detection of Cu²⁺and Cr³⁺by a simple Schiff-base colorimetric chemosensor bearing NBD (7-nitrobenzo-2-oxa-1,3-diazolyl) and julolidine moieties

A new NBD (7-nitrobenzo-2-oxa-1,3-diazolyl) and julolidine-based chemosensor 1 was designed and synthesized as a colorimetric chemosensor for Cu²⁺and Cr³⁺. The presence of Cu²⁺and Cr³⁺led to distinct visible color changes from violet to yellow and blue, respectively, in aqueous solution. To examine the binding mechanisms of 1 with Cu²⁺and Cr³⁺, UV–vis spectroscopy, ESI-mass spectrometry analysis and DFT calculations were conducted. The detection limits for the analysis of Cu²⁺and Cr³⁺ions were found to be 0.36 μM and 0.59 μM, respectively. Practically, sensor 1 functioned as a visible test strip for Cu²⁺and Cr³⁺. Moreover, the sensing abilities of 1 for Cu²⁺and Cr³⁺were successfully carried out in real water samples. Therefore, sensor 1 can be employed as a practical colorimetric chemosensor for detecting both Cu²⁺and Cr³⁺.