Selective and sensitive colorimetric sensor for CN- in the absence and presence of metal ions (Cu2+/Ni2+): mimicking logic gate behaviour

Enone based anion sensors have significance due to their colorimetric reaction upon deprotonation and variable occurrence in the conjugated moiety. We have designed a novel and easily forming cromene-isonicotinohydrazide based probe, exhibiting selectivity towards CN- through the naked eye. A Job's plot displays 1 : 1 stoichiometry along with a 0.76/0.68 mu M detection limit. The results accentuate that upon addition of cations (Cu2+/Ni2+) to the heteroatom of donor moiety, sensitivity improves. The limits of detection were found to be 3.5/6.3 mu M in the presence of Cu2+/Ni2+. The mechanism was proved by FTIR, NMR, DFT and -OH titration.