Intramolecular charge-transfer process based on dicyanomethylene-4H-pyran derivative:: An integrated operation of half-subtractor and comparator

Integration of simple logic gates into combinational circuits is a crucial step for the performance of arithmetic systems and working automation. A half-subtractor has been reported in combination with a Comparator based on the intramolecular charge transfer (ICT) process resulting from hosting two different guests with the binding of Zn2+ and the deprotonation of phenolic hydroxyl groups in an unimolecular system. The corresponding spectral shifts in absorption and a variation in fluorescence intensity were well elucidated. An XOR (exclusive OR) logic gate generates the difference digit of the half-subtractor reading at 445 nm, and two INHIBIT logic gates, which are basically AND gates with one of the inputs inverted through a NOT function, are achieved for the borrow digit of the half-subtractor when the output signals are monitored at 400 and 525 nm. Taken together, the comparison and subtraction operations are practically performed in parallel without mutual interference due to the same inputs and different outputs within the same molecule system.