Three-State Biaryl Lactone Molecular Switches with Amine Donors

Abstract

Our research is focused on the synthesis of four bridged biphenyl molecules with amine donors. These three-state biphenyl molecules, due to their chemical properties, should have various uses within chemical and electronic fields. Biphenyl molecules have known dihedral angles, leading to differing optical and conducting properties when manipulated. By using a lactone-bridge we can force the molecule into and out of planarity; at low pH the molecule takes a planar conformation (“ON”), while at high pH it's non-planar (“OFF”). Research from previous groups has shown similar two-state molecules’ effectiveness at readily switching conformations when exposed to different chemical environments.1 We are researching the addition of diethylamine and diphenylamine donor groups. By combining cyano and nitro acceptors used previously and differing amino donors within biphenyl molecules, we can enhance optical properties and pH sensitivity. This pH sensitivity will be more precise with the addition of a third “OFF” of the molecule. At low pH, the amino group should become protonated, leading to the second “OFF” state and giving the molecule a narrow “ON” state. The “ON” state would result in visible color differences than the “OFF” state of the molecule. These characteristics would improve usefulness of these molecules as pH sensors.