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.
- Imaging agents