Multi-Readout Logic Gate for the Selective Detection of Metal Ions at the Parts Per Billion Level

Optical sensors utilizing visual responses for the identification of metal ions require reliable molecular systems able to operate selectively in multicomponent solutions. Herein, we report a water-soluble terpyridyl-based ligand that demonstrates effective quantification of parts per billion to parts per million levels of Fe2+, Fe3+, Zn2+, and Ru3+. Whereas the Fe3+ and Ru3+ ions were found to bind to the ligand to form a monometallic complex, a 2:1 ligand/metal binding stoichiometry was found for the Zn2+ and Fe2+ complexes. The corresponding metal-binding events were directly translated into distinct colorimetric and spectroscopic logic outputs. Applying molecular logic (Boolean logic operations) to describe these binding events, selective discrimination between the ions was demonstrated.