Turn-On Ratiometric Fluorescent Probe for Selective Discrimination of Cr(3+) from Fe(3+) in Aqueous Media for Living Cell Imaging.

Pyrene-based turn-on ratiometric fluorescent probe 1 demonstrates high sensitivity and exceptional selectivity toward Cr(3+) in the presence of other metals, including Fe(3+) in aqueous media. Interaction of Cr(3+) with probe 1 brings pyrene moieties close enough to have better aligned π-π stacking, thus enhancing the excimer peak many fold. On the other hand, the interaction of Fe(3+) with probe 1 brings forth a negligible difference in stacking, resulting in an insignificant change in fluorescence intensity. Exceptional selectivity of probe 1 with Cr(3+) over Fe(3+) and other metals has been confirmed by theoretical studies in addition to experimental results. Imaging of HeLa cells observed by confocal fluorescence microscopy reveals that probe 1 can be used to monitor Cr(3+) in live cells to map its subcellular distribution.