Supramolecular self-assembly of chiral helical tubular polymers with amplified circularly polarized luminescence

Abstract

Highly programmed self-assembly of supramolecular architectures with circularly polarized luminescence (CPL) has been a big challenge in developing chiroptic materials. We report here self-assembly of two chiral tubular supramolecular structures based on arrays of helices built from chiral bispyridyl biphenol-/spinol-phosphoric acid. Organic molecules integrated in the double or triple helical structures display obviously enhanced Cotton effects and CPL emissions. The polymers afford a two to three-fold increase of the luminescence dissymmetry factor |g_lum| in solutions, which reach as high as 3.5 × 10⁻³, due to the amplification effect of CPL arising from the strong intermolecular couping of organic monomers. In solution, the handedness of CPL is determined by the inherent chirality of organic monomers. In the solid state, the CPL signal of one polymer is kept and reversed, which follows the handedness of the helical assembly, whereas the signals of another disappeared owing to an aggregation-caused quenching effect. These two polymers are rare examples of CPL supramolecular materials having been crystallographically characterized. This study provides insights into a structural and molecular basis for designing ordered polymeric structures with advanced chiroptic properties.