Noticeable Chiral Center Dependence of Signs and Magnitudes in Circular Dichroism (CD) and Circularly Polarized Luminescence (CPL) Spectra ofall-trans-Poly(9,9-dialkylfluorene-2,7-vinylene)s Bearing Chiral Alkyl Side Chains in Solution, Aggregates, and Thin Films

Abstract

Effects of chiral alkyl side chains in poly(9,9-dialkyl-fluorene-2,7-vinylene)s [PFVs, (S)-3-methylpentyl (3mpe), (S)-4-methylhexyl (4mhex), (S)-5-methylheptyl (5mhep), (S)-6-methyloctyl (6moct), and (S)-3,7-dimethyloctyl (dmo)] toward aggregation-induced circular dichroism (AICD) and circularly polarized luminescence (AICPL) and CD/CPL spectra in solution and in thin film have been explored. The (all-trans) PFV samples with similar conjugation repeat units containing well-defined (vinyl) end groups were prepared by acyclic diene metathesis polymerization using Ru catalyst. The PFV aggregates, prepared in situ in a mixed solution of CHCl3/MeOH, showed clear CD signals ascribed to AICD, whereas these samples showed CD-silent in the CHCl3 solution. The absolute magnitude (gCD value) was affected by the chiral side chains (without obey the even–odd rule) and increased in the order 3mpe, 5mhep < 4mhex < dmo < 6mcot. Both the 6-moct and dmo aggregates showed clear CPL signals ascribed to AICPL, whereas signals...