Synthesis and evaluation of two novel rhodamine-based fluorescence probes for specific recognition of Fe c+ ion

Two low cytotoxic fluorescence probes Rb1 and Rb2 detecting Fe 3+ were synthesized and evaluated. Rb1 and Rb2 exhibited an excellent selectivity to Fe 3+ , which was not disturbed by Ag + , Li + , K + , Na + , NH 4 + , Fe 2+ , Pb 2+ , Ba 2+ , Cd 2+ , Ni 2+ , Co 2+ , Mn 2+ , Zn 2+ , Mg 2+ , Hg 2+ , Ca 2+ , Cu 2+ , Ce 3+ , AcO − , Br − , Cl − , HPO 4 2− , HSO 3 − , I − , NO 3 − , S 2 O 3 2− , SO 3 2− and SO 4 2− ions. The detection limits were 1.87 × 10 −7 M for Rb1 and 5.60 × 10 −7 M for Rb2 , respectively. 1:1 stoichiometry and 1:2 stoichiometry were the most likely recognition mode of Rb1 or Rb2 towards Fe 3+ , and the corresponding OFF–ON fluorescence mechanisms of Rb1 and Rb2 were proposed.