Phenazine containing indeno-furan based colorimetric and “on-off” fluorescent sensor for the detection of Cu2+ and Pb2+

A new fluorescent sensor 10a,15a-dihydroxy-10aH-benzo[a]indeno[2′,1′:4,5]furo[2,3-c]phenazin-15(15aH)-one (1) based on the combination of phenazine and indenofuran moieties was designed and synthesized. Structure of the synthesized sensor has been confirmed by X-ray crystallographic analysis. Absorption and emission spectra of 1 has been studied in solvents of different polarity. The solvent effect on the spectral properties of 1 has been investigated by using the Lippert-Mataga and Reichardt-Dimroth methods. It exhibits high sensitivity and selectivity towards Cu2+ and Pb2+ ions over other metal ions by fluorescence quenching. Sensor 1 exhibited a visible color change from light orange to pink, and yellow in the presence of Cu2+ and Pb2+, respectively. The fluorescence of the 1-Cu2+/Pb2+ complexes can be reversibly restored to that of the uncomplexed ligand by using EDTA. Binding stoichiometry and mechanism of Cu2+ and Pb2+ ions detection have been investigated. The linear range for the synthesized sensor was found to be 1×10−6-6.31×10−5 M with detection limit of 1.3×10−6 M. Theoretical calculations were employed to understand the sensing mechanism of the sensors towards Cu2+.