Triple-signaling mechanisms-based three-in-one multi-channel chemosensor for discriminating Cu2+, acetate and ion pair mimicking AND, NOR, INH and IMP logic functions

Chemosensor 1 shows three different responses towards Cu2+, acetate and Cu(OAc)(2) ion pair at different wavelengths independently in its absorption and fluorescence behaviour following a triple-signaling mechanism, namely, internal charge transfer (ICT), CQN rotation and excited state intramolecular proton transfer (ESIPT). Chemosensor 1 shows a blue shift of the absorption band from 337 nm to 308 nm in the presence of Cu2+ ions (ICT). It exhibits a fluorescence 'urn-off' response at lambda(em) 458 nm in the presence of 1 equivalent of Cu2+ ions. The further addition of Cu2+ (6 equivalents) results in similar to 24 times enhancement in the emission intensity at lem 427 nm, mimicking an 'N-OFF-ON' molecular switch (ESIPT and CQN rotation). The addition of acetate ions to a solution of 1 results in a red shift of the absorption band from 337 to 360 nm (ICT) and similar to 4 times enhancement of the emission intensity at lambda(em) 458 nm (ESIPT). On the addition of a Cu(OAc)(2) ion pair, 1 shows the apparent effect of Cu2+ (blue shift, 337 to 308 nm) and acetate (red shift, 337 to 380 nm), which indicates the synergistic effect of both Cu2+ and AcO- on each other's binding. The potential application of chemosensor 1 for the construction of INHIBIT (INH), IMPLICATION (IMP), AND, NOR, YES and NOT logic gates using Cu2+ and acetate as the inputs and absorbance/emission as the outputs is elaborated.