Molecular Logic Gates and Switches Based on 1,3,4-Oxadiazoles Triggered by Metal Ions

Organic molecular devices for information processing applications are highly useful building blocks for constructing molecular-level machines. The development of intelligent molecules capable of performing logic operations would enable molecular-level devices and machines to be created. We designed a series of 2,5-diary1-1,3,4-oxadiazoles bearing a 2-(para-substituted)phenyl and a 5-(o-pyridyl) group (substituent X = NMe2, OEt, Me, H, and Cl; 1a-e) that form a bidentate chelating environment for metal ions. These compounds showed fluorescence response profiles varying in both emission intensity and wavelength toward the tested metal ions Ni, Cu2+, Zn2+, Cd2+, Hg2+, and Pb2+ and the responses were dependent on the substituent X, with those of 1d being the most substantial. The 1,3,4-oxadiazole O or N atom and pyridine N atom were identified as metal-chelating sites. The fluorescence responses of 1d upon metal chelation were employed for developing truth tables for OR, NOR, INHIBIT, and EnNOR logic gates as well as ON-OFF-ON and OFF-ON-OFF fluorescent switches in a single 1,3,4-oxadiazole molecular system.