Oligoethylene Glycol Substituted Isomeric Pi- Expanded Coumarins with Crankshaft Architectures

Abstract

The physical properties of terphenyl-containing compounds are known to be highly dependent on molecular geometry, specifically the dihedral angle. Compounds capable of dihedral angle modulation should be useful molecular switches. Planar conjugated aromatics have desirable optical and electronic properties, whereas these properties are highly attenuated in non-planar analogs. Unfortunately, planar compounds tend to be insoluble in most organic solvents. We have synthesized several terphenyl dilactones containing solubilizing substituents, where the two lactones “tether” between the two phenyl rings should force a planar geometry. By varying the pH or redox conditions, we should be able to reversibly and rapidly open and close the “tether” and switch the molecule in and out of planarity. We will describe the synthesis and characterization of these compounds as well as show preliminary studies of their pH and redox switching. More recent work has been directed at the solubility of these lactone switches and trying to improve the solubility with oligoethylene glycols groups. This particular 4 step reaction begins with 2,4-dihydroxybenzoic acid and undergoes bromination and decarboxylation to create 5-bromoresorcinol. The phenol groups of the compound will be protected to be converted into a pinacol boronate ester and Suzuki coupling will produce the desired crankshaft pi-expanded oligocoumarin.