Abstract
CQHC, a novel colorimetric fluorescent sensor, developed for the selective sensing of ions and well characterised, including SC-XRD. It demonstrated selective sensing for Co(2+), Zn(2+), Hg(2+) and F(-) using absorbance titration at 420 nm, 446 nm and the binding constants estimated follows the order F(-) > Co(2+) > Hg(2+) > Zn(2+). On light of this, molecular logic gate was built for CQHC's selective multi-ion detection. However, fluorescence titration analysis revealed that CQHC is solely selective for F(-) ions. This conclusion was validated by (1)H-NMR titration, clearly showed deprotonation occurs from N(3)-H. Fluorescent decay titration, kinetic investigations and computational studies all contributed to the selective sensing of F(-). According to TD-DFT calculations, added fluoride ion interacts with N(3)-H proton and deprotonates to generate F-H in the excited state.