Sunlight-induced degradation of squarazine-based cyanide complex through imine CN free rotation: Sensing, binding and degradation studies of anionic complex

Sunlight-induced degradable squarazine based electron deficient receptor 3,4-bis((E)-2-((perfluorophenyl)methylene)hydrazinyl)cyclobut-3-ene-1,2-dione, L has been reported here. Naked-eye colorimetric analysis, UV-Vis, IR and ¹H, 19F, ³¹P-NMR spectrometric results show that this receptor L high affinity with cyanide anion. The strength of the receptor L towards colorimetrically responded anions are calculated by UV-Vis spectrometric titrations and it is found to be 9.9597 × 10³ for cyanide. Interestingly, upon exposure of those anionic complexes under sunlight, the colors of those respective anionic complexes are disappeared. From this result, it is clear that these anionic complexes are capable to discharge the bound anion via CN free rotation. As evidenced from spectroscopic and colorimetric results, it is also clear that this anionic complex is not only release the bound anion, but also undergone self-degradation upon sunlight exposure. To the best of our knowledge, this is the first example for cyanide sensing of anion accomplished with self-degradation of anion complex upon exposure on sunlight.