Colorimetric and fluorimetric response of salicylaldehyde dithiosemicarbazone towards fluoride, cyanide and copper ions: Spectroscopic and TD-DFT studies.

The sensing mechanism of salicylaldehyde phenyldithiosemicarbazone (SDTSC) chemosensor has been investigated by spectroscopic and TD-DFT methods. The SDTSC shows colourimetric and spectral changes towards fluoride, cyanide and copper ions. The interaction between SDTSC with fluoride, cyanide and copper ions was examined through their absorption and fluorescence behaviour, and found that SDTSC has more sensing ability towards Cu2+ ion than CN- and F- ions. The1 H NMR titration with SDTSC and F- gives the structural changes in the sensing process. The reversibility of SDTSC was also evaluated and thus it is confirmed as a reusable chemosensor which can be clarified by the "Read-Erase-Read-Write" logic system. The DFT and TD-DFT calculations give the detailed sensing mechanism of SDTSC towards fluoride ion. The potential energy surface (PES) analysis confirms the excited state electron transfer mechanism.