A Highly Selective "Turn-on" Fluorescent Probe for Detection of Fe in Cells.

A new "turn-on" fluorescent probe Py based on rhodamine and piperonaldehyde was designed and synthesized for detecting Fe in cells. The free probe Py was non-fluorescent. While only upon addition of Fe, the significant increase of the fluorescence and color were observed which could be visible directly by "naked-eye". The probe Py shows high selectivity and sensitivity for Fe over other common metal ions in EtOH-HO (3/2, v/v) mixed solution. The association constant and the detection limit were calculated to be 4.81 × 10 M and 1.18 × 10 mol/L respectively. The introduction of piperonaldehyde unit could increase probe rigidity which could enhance its optical properties. Meanwhile, the binding mode between Py and Fe was found to be a 1:1 complex formation. The density functional theory (DFT) calculations were performed which would further confirm the recognition mechanism between probe Py and Fe. In addition, the probe has been proved to be reversible for detecting Fe. Moreover, the probe Py was used to detect Fe in cells successfully.