Ethyl 3-aminobenzo[b]thiophene-2-carboxylate Derived Ratiometric Schiff Base Fluorescent Sensor for the Recognition of In3+ and Pb2+

An ethyl 3-aminobenzo[b]thiophene-2-carboxylate derived ratiometric Schiff base fluorescent sensor R was devised and synthesized. R exhibited a highly sensitive and selective ratiometric response to In3+ in DMF/H2O tris buffer solution. R exhibited a colorimetric/fluorescent dual-channel response to In3+. More importantly, R can distinguish In3+ from Ga3+ and Al3+ in less than 5 min. R exhibited a good linear correlation with the concentration of In3+ in the 5-25 mu M range and the limit of detection for In3+ was found to be 8.36 x 10(-9) M. According to the job`s plot and MS spectra, R formed a complex with In3+ at 1:2 with a complexation constant of 8.24 x 10(9) M-2. Based on Gaussian theory calculations, the response mechanism of R to In3+ can be explained by photo-induced electron transfer (PET) and intramolecular charge transfer (ICT) mechanisms. In addition, R can be used for the detection of indium in tap water with satisfactory recoveries. Meanwhile, R displayed a linear relationship to micromolar concentrations (0-50 mu M) of Pb2+ and recognized Pb2+ in a ratiometric response with a detection limit of 8.3 x 10(-9) M.