Triazole-based novel bis Schiff base colorimetric and fluorescent turn-on dual chemosensor for Cu 2+ and Pb 2+ : application to living cell imaging and molecular logic gates.

A triazole-based novel bis Schiff base colorimetric and fluorescent chemosensor (L) has been designed, synthesized and characterized by elemental analysis, 1 H-NMR, ESI-MS, FTIR spectra and DFT studies. The receptor L showed selective and sensitive colorimetric sensing ability for Cu 2+ and Pb 2+ ions by changing color from colorless to yellow and light yellow respectively in CH 3 OH-tris-buffer (1 : 1, v/v). However, it displayed strong fluorescence enhancement upon the addition of both Cu 2+ and Pb 2+ ions, attributed to the blocking of PET. The fluorometric detection limits for Cu 2+ and Pb 2+ were found to be 12 × 10 -7 M and 9 × 10 -7 M and the colorimetric detection limits were 3.7 × 10 -6 M and 1.2 × 10 -6 M respectively; which are far below the permissible concentration in drinking water determined by WHO. Moreover, it was found that chemosensor L worked as a reversible fluorescence probe towards Cu 2+ and Pb 2+ ions by the accumulation of S 2- and EDTA respectively. Based on the physicochemical and analytical methods like ESI-mass spectrometry, Job plot, FT-IR, 1 H-NMR spectra and DFT studies the detection mechanism may be explained as metal coordination, photoinduced electron transfer (PET) as well as an internal charge transfer (ICT) process. The sensor could work in a pH span of 4.0-12.0. The chemosensor L shows its application potential in the detection of Cu 2+ and Pb 2+ in real samples, living cells and building of molecular logic gate.