A highly selective optical probe for sensing of Fe 3+ based on a water-soluble croconaine

Abstract

Abstract A highly selective water-soluble optical probe, 2,5-bis[2,3,3-trimethyl-3 H -indole-5-sulfonic acid]-croconaine ( TISC ) was successfully synthesized. TISC can efficiently recognize Fe 3+ with the existence of competing cations (Na + , Mg 2+ , Al 3+ , Cr 3+ , Zn 2+ , K + , Ca 2+ , Ba 2+ , Pb 2+ , Ni 2+ , Co 2+ , Ag + , Cu 2+ , Cd 2+ ) in deionized water. The binding constant ( K a ) of TISC- Fe 3+ was calculated to be about 3.071 × 10 4 M −1 . Correspondingly, the chelating mode of TISC -Fe 3+ was confirmed by Job’s plot, FT-IR and 1 H NMR. Moreover, Fe 3+ and EDTA could be employed as inputs and the absorbance which was 745 nm as output so that a molecular logic gate could be realized, and the test strips of TISC showed a high selectivity to Fe 3+ .