Fluorescence 'on-off-on' chemosensor for sequential recognition of Fe 3+ and Hg2+ in water based on tetraphenylethylene motif

A novel selective and sensitive fluorescence ‘on-off-on’ probe based on tetraphenylethylene (TPE) motif for sequential recognition of Fe3+ and Hg2+ in water has been developed. Especially the complex 6-Fe3+ could behave as a ‘turn on’ fluorescent sensor over a wide-range pH value for detection of Hg2+. The selectivity of this complex for Hg2+ over other heavy and transition metal ions is excellent, and its sensitivity for Hg2+ is at 2ppb in water.