Pi-Expanded Coumarins with Switchable Propeller Geometries

Abstract

The focus of this project is analyzing planar conjugated molecules as molecular geometric switches. Our mission is to synthesize and study different classes of pi-expanded oligocoumarins with Crankshaft and Propeller architectures. The aryl-aryl torsional angle of the oligopheny subunits is controlled by lactone bridging groups to force planar conjugation. The lactone bridges could be reversibly cleaved and re-formed by changes in pH to form an open and closed conformation. Planar compounds with extended pi-conjugation suffer from poor solubility due to strong pi-stacking interactions. The synthesis with various solubilizing groups and switching studies of these compounds could lead to applications in areas such as organic electronics, molecular machines, light-harvesting materials, drug administration and sensors.