Axially Chiral Spiro-Conjugated Carbon-Bridged p-Phenylenevinylene Congeners: Synthetic Design and Materials Properties

Spiro-conjugated systems are attracting considerable interest for their chiroptical properties and because of their compact structure the small reorganization energy upon electronic excitation or ionization. We report here a modular and convergent synthesis of axially chiral spiro-conjugated carbon-bridged p-phenylenevinylenes (spiro-CPVs) in a racemic and optically active form where two carbon-bridged p-phenylenevinylene molecules are connected by a spiro carbon atom. Our synthetic design focuses on the C2 symmetry of the spiro-CPV molecules, relying on coupling of two 3-lithio-2-arylindene molecules on a carbon monooxide molecule that serves as the spiro carbon center in the target molecule. We prepared derivatives including those possessing phenol groups that facilitate optical resolution and also serve as a platform for the synthesis of a variety of optically active derivatives, which exhibit circularly polarized photoluminescence with high fluorescence quantum yields, large dissymmetry factors, and h...