Dithiolane linked thiorhodamine dimer for Hg ²⁺ recognition in living cells

Thiorhodamine-based chemodosimeter A, a disulfide linked dimer, was designed for Hg ²⁺ recognition by virtue of the strong affinity of mercury for sulfur. Spectroscopic results reveal that chemodosimeter A exhibits real-time responses, and high sensitivity and selectivity for Hg ²⁺ in comparison to other cations. These properties are mechanistically ascribed to the transfer from rhodamine spirolactam to the thiazoline-derived open-ring rhodamine via Hg ²⁺ induced desulfurization. The in vitro recognition of Hg ²⁺ in living cells pretreated with A was examined, showing that the concentration of Hg ²⁺ that could be imaged reaches the safety limit for human beings.