New water-soluble highly selective fluorescent chemosensor for Fe (III) ions and its application to living cell imaging

Abstract A new rhodamine-based chemosensor exhibits excellent selectivity for Fe 3+ ions over a wide range of tested metal ions Ag + , Al 3+ , Ca 2+ , Cd 2+ , Co 2+ , Cr 3+ , Cu 2+ , Fe 2+ , Hg 2+ , Mg 2+ , Mn 2+ , Ni 2+ , Pb 2+ , and Zn 2+ in an aqueous solution. The binding of Fe 3+ to chemosensor 1 produces an absorption band at 564 nm and an emission band at 588 nm because Fe 3+ -binding induces ring-opening of the spirolactam in 1 . The binding ratio of the 1 –Fe 3+ complexes was determined to be 1:1 according to a Job plot. The association constant ( K a ) of Fe 3+ binding in chemosensor 1 was 6.9 × 10 3  M −1 . The maximum fluorescence enhancement caused by Fe 3+ binding in chemosensor 1 occurred at a pH range of 6–7.5. The fluorescence microscopy experiments in this study demonstrated that chemosensor 1 can be used as a fluorescent probe for detecting Fe 3+ in living cells.