A per-acetyl glycosyl rhodamine as a novel fluorescent ratiometric probe for mercury (II)

•A per-acetyl glycosyl rhodamine probe detects Hg2+ in a ratiometric manner.•The fluorescent acetyl glycosyl moiety of the probe serves as a FRET donor.•The probe is highly specific for Hg2+ in an 80% aqueous solution.•A plausible mechanism for the detection is proposed.

This paper describes the identification of a per-acetyl glycosyl rhodamine B (RB) derivative, KB2, simply prepared by a click reaction, as a novel fluorescent ratiometric probe for mercury (II). In an 80% aqueous solution, KB2 responded to Hg2+ in a ratiometric manner with a good selectivity over a range of metal cations. Upon formation of a 1:1 probe-ion complex, the blue fluorescence of the per-acetyl glycosyl moiety of KB2 is quenched, along with the emergence of a bright red fluorescence attributable to the lactam ring-opening form of RB. This is probably caused by a fluorescence resonance energy transfer from the acetyl glycoside as a donor to the acceptor RB–Hg2+ motif. This study provides unique insight into the design of ratiometric chemoprobes for heavy metals based on the simple coupling of per-acetyl glycosides with fluorogenic dyes.

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