Ambidextrous circular dichroism and circularly polarised luminescence from poly(9,9-di-n-decylfluorene) by terpene chirality transfer

Abstract

Solvent chirality transfer using enantiomeric pairs of limonene and α-pinene allowed for the successful production of optically active poly(9,9-di-n-decylfluorene) (PF10) aggregates with circular dichroism (CD) and circularly polarised luminescence (CPL) properties. The aggregates were rapidly produced by CD-/CPL-silentPF10 with the aid of solvent chirality transfer at 25 °C. We demonstrate that: (i) through weak forces, such as π/π, van der Waals, and CH/π interactions, CD-/CPL-active PF10 aggregates successfully emerge in a chiral tersolvent system of chloroform (as a good solvent), alkanol (as a poor solvent), and terpenes (as a chiral solvent), (ii) the molecular weight of PF10, alkyl chain length of PFs, terpene structure and enantiopurity, solvent type, and solution temperature greatly affect the magnitude and sign of the CD-/CPL-signals, (iii) the vortex and aggregate size only mildly affect the magnitude of these signals, and (iv) a new CPL band at 434 nm from PF10 aggregates, arising from the CD/UV-vis band at 428 nm, may result from a chiral β-phase. The terpene chirality transfer demonstrated herein may provide a new environmentally friendly, safer, and milder process to rapidly produce ambidextrous chiroptical polymeric materials at ambient temperature from CD-/CPL-silentpolymers without any specific chiral catalysts or substituents.