Our research is focused on the synthesis of a bridged biphenyl molecule with an amino donor, cyano acceptor, and tetraethylene glycol solubilizing groups (TEG). This three-state biphenyl molecule could find applications like nanoscale fluorescent sensors and molecular mechanical devices. Biphenyl molecules have known dihedral angles, leading to differing optical and conducting properties when manipulated. Utilizing a lactone-bridge, we can force the molecule into and out of planarity by changing pH: at low pH, the molecule takes a planar conformation (“ON”) due to the lactone bridge being intact, while at high pH it adopts a non-planar (“OFF”) geometry resulting from lactone cleavage. Planar biphenyl-containing systems often suffer from poor solubility and thus limited application. However, addition of TEG solubilizing groups will aid in their synthesis, study, and application due to enhanced solubility. Previous research in our group has shown analogous two-state biaryl lactone systems to readily switch conformations when exposed to different pH environments. This pH sensitivity will be even more precise with the addition of a third “OFF” state. At low pH, the amino donor group should become protonated, leading to the second “OFF” state and giving a narrow “ON” state. The “ON” state results in visible color and fluorescence differences from the “OFF” states of the molecule. We will be reporting on the synthetic progress of these molecules as well as evidence supporting their use as three-state molecular switches.
