Single molecular platform displaying PET and hydrolysis sensing mechanism for differential detection of metal ions

The development of single molecular chemosensor with chromo-fluorescent properties have advantages of easy and cost-effective analysis. Moreover, designing and synthesizing such chemosensors for multi-metal ions has become a challenge. We have designed a new NBD based dyad with dual channel mode as a chromogenic sensor for Cu2+, and a fluorogenic sensor for Al3+ and Hg2+ ions. The dyad 1 showed the absorption peaks at 475 nm, 440 nm and 320 nm. In the presence of Cu2+ ions, dyad 1 showed an instant colour change from yellow to blue with a redshift of 150 nm to new absorption band at 595 nm. However, the weak emission of dyad 1 at 355 nm showed a turn-on response for Hg2+ and Al3+ ions. In the presence of Hg2+ ions, dyad 1 showed emission enhancement at 355 nm. Whereas, the presence of Al3+ ions from 0 to 4 mu M, increase in intensity at 355 nm and on further addition of Al3+ ions from 4 to 15 mu M, quenching at 355 nm with the concomitant increase in intensity at 445 nm was observed. The detection limit of Cu2+ ions was found to be 17.6 nM, and Hg2+/Al3+ was 20 nM/67.6 nM. Further, the DFT calculation was performed to complement the experimental results. Thus, dyad 1 showed the chromogenic response for Cu2+ and fluorogenic response for Al3+ ions.