A novel C3v-symmetric completely water soluble turn-on chemo sensor for Cd2+ and the resultant complex for iodide anion in aqueous medium

• Turn-on fluorescence and colorimetric Cd2+ sensor.
• The sensing is done in 100% aqueous medium.
• Iodide anion sensing through metal complex ensembles.
• Sensing of Cd2+ in environmental samples.

A novel simple C3v-symmetric, completely water soluble quinoline based guanidinium Schiff's base system have been reported for the selective detection of Cd2+ in physiological environment through a turn-on fluorescence response. The cadmium complex is found to be highly selective toward iodide by turning off the fluorescence through the sequestration of Cd2+ from L1-Cd by the precipitation of CdI2. Detection limit for Cd2+ and iodide are found to be 51 ppb and 1 ppb, respectively. L1 is reversible toward Cd2+ and iodide and can be recycled. The receptor was used for the detection of Cd2+ in complex natural samples (tap, lake and river water).