The fluorophores based on xanthene scaffolds, mainly containing rhodamine and fluorescein dyes, have attracted considerable interest from chemists due to their excellent photophysical properties such as high absorption coefficient, high fluorescence quantum yield, high photostability and relatively long wavelengths of fluorescence emission spectra. In this feature article, we overview the strategies in the development of fluorescent probes that are operating through the modification of the skeletons of fluorescein and rhodamine dyes, and the fluorescent behaviors of these probes toward specific analyte are discussed.

Based on a T-Hg(2+)-T binding mode, a sensitive ratiometric fluorescent chemosensor for aqueous Hg(2+) was developed with a heptamethine cyanine chromophore containing a thymine moiety.

A new rhodamine spiro scaffold with a six-membered reactive ring was developed by inserting a nitrogen atom in the known probe rhodamine B spiro thiohydrazide, which switched the recognition preference of the probe from Hg(2+) to Cu(2+). This probe is shown to be an efficient "turn-on" fluorescent chemodosimeter for Cu(2+) in a neutral aqueous medium. Mechanism studies suggested that the probe opened its spiro-ring by a Cu(2+)-induced transformation of the cyclic thiosemicarbazide moiety to an isothiocyanate group.

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Advances in Modifying Fluorescein and Rhodamine Fluorophores as Fluorescent Chemosensors -[88 refs.]. -(ZHENG*, H.; ZHAN, X.-Q.; BIAN, Q.-N.; ZHANG, X.-J.; Chem. Commun. (Cambridge) 49 (2013) 5, 429-447, http://dx.doi.org/10.1039/c2cc35997a ; Dep. Chem., Xiamen Univ., Xiamen 361005, Fujian, Peop. Rep. China; Eng.) -S. Karsten 16-220