Novel highly selective fluorescent chemosensors for Hg(II)

Based on Rhodamine, two novel fluorescent Hg2+ chemosensors(R1, R2) were synthesized from inexpensive starting materials. They were designed and synthesized with o-aminophenol and o-phenylenediamine derivatives as the Hg2+ chelator, the comparison between the photophysical properties of two chemosensor molecules was made. The chemosensors were designed with a photoinduced electron transfer(PET) mechanism. After binding to Hg2+ which blocks the PET process, the fluorescence intensity of the chemosensors was enhanced by up to 15-fold. They exhibit very strong fluorescence responses to Hg2+ and have remarkably higher selectivity for Hg2+ than for other metal ions including K+, Na+, Ca2+, Mg2+, Cd2+, Mn2+, Ni2+, Co2+, Zn2+, Cu2+, Cr3+, Fe3+, Pb2+, Ag+, Al3+, Fe2+ and Sn2+ in Tris-HCl/sodium phosphate buffer. The fluorescence enhancement of R2 towards Hg2+ maintains stable in wide pH span(6.4–8.8) aqueous solutions.