CHEF induced highly selective and sensitive turn-on fluorogenic and colorimetric sensor for Fe3+

A new fluorescent probe was synthesized from rhodamine-6G and 6-(hydroxymethyl) picolinohydrazide for the sensing of Fe3+ in an aqueous environment. The structure of the sensor was confirmed through its single crystal X-ray study. It exhibits a high specificity and sensitivity towards Fe3+ over other interfering heavy and transition metal ions (HTM). The turn-on greenish-yellow fluorescence and a colorimetric change from colourless to pink were observed upon addition of Fe3+ which evokes almost 116-and 23-fold enhancement in absorbance and emission intensity respectively in an acetonitrile-water (1:1, v/v, 25 degrees C) solution at a neutral pH (pH = 7.2). The Fe3+ promoted ring opening of the spirolactam framework to the open chain amide platform of the sensor is responsible for its visible colour change and turn-on fluorescence activity. It also exhibits an excellent performance in the dip stick method. Moreover the limit of detection of the probe is in the 10(-8) M range.