Differential response for multiple ions: a smart probe to construct optically tunable molecular logic systems.

A rhodamine-based optical probe has been designed through a one-pot synthetic protocol involving phenanthroline as a binding motif. The compound showed a bright pink coloration specifically upon the addition of Cu and Hg ions. However, the appearance of bright red fluorescence was observed only in the presence of Hg. Considering both, we can detect and discriminate these two ions even at ppb level concentration. Furthermore, these generated metal complexes were utilized for the selective recognition of CN and I ions. Pre-coated TLC plates were developed for rapid on-site detection of these toxic ions even in remote places. Finally, on a single molecular probe based on differential opto-chemical interactions with different ions (Cu, Hg, CN and I), we were able to design numerous trivial (OR, NOR) and non-trivial (INHIBIT, IMPLICATION, COMPLEMENT, TRANSFER, NOT-TRANSFER) logic gates. Most fascinatingly, we can switch the logic response from one type to another by simply tuning only the optical output channel.