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.