A reversible fluorescent chemosensor for iron ions based on 1H-imidazo [4,5-b] phenazine derivative

Two kinds of fluorescent sensors (G1 and G2) for Fe3+ bearing 1H-imidazo [4,5-b] phenazine derivatives have been designed and synthesized. G1 can display ON-OFF-type fluorescence charged with high selectivity and sensitivity toward Fe3+ in DMSO solutions. And other cations, including Hg2+, Ag+, Ca2+, Co2+, Ni2+, Cd2+, Pb2+, Zn2+, Cr3+, and Mg2+ had no influence on the probing behavior. The detection limit of the sensor G1 towards Fe3+ is 2.860 × 10−7 M. Once combined with Fe3+, G1 displayed high specificity for H2PO4−. Furthermore, in the situ generated G1–Fe3+ ensemble could recover the enhanced fluorescence upon the addition of H2PO4− resulting in an ON-OFF-ON sensing with a detection limit of 1.866 × 10−7 M in the same medium. Notably, this sensor serves as a recyclable component in sensing materials. The reversibility and selectivity of G1/G1 + Fe3+ toward Fe3+/H2PO4− ions as a sequence dependent molecular keypad lock using the G1, Fe3+ and H2PO4− as three different chemical inputs. In addition, the test strip based on G1 was fabricated, which could act as a convenient and efficient Fe3+ test kit.