Chiral benzo[ghi]perylene substituted [n]helicenes with strong blue fluorescent emission and circularly polarized luminescence

Abstract

Chiral organic fluorescent molecules with circularly polarized luminescence (CPL) properties have attracted much attention for their potential applications in chiral optical and electronic devices. Benzo [ghi]perylene is one of the classical polycyclic aromatic hydrocarbons (PAHs) with good fluorescent properties and has many applications in the fields including optoelectronic devices and fluorescence probes. In this work, chiral benzo [ghi]perylene substituted [n]helicenes were directly obtained from chiral BINOL. The introduction of benzo [ghi]perylene structure greatly improved the fluorescent efficiency of the pristine helicene molecules. These benzo [ghi]perylene substituted [n]helicenes show strong blue fluorescent emission in organic solutions with good fluorescent quantum yields. These molecules could also exhibit moderate fluorescent emission in the solid-states. Based on the DFT calculations results, the HOMOs and LUMOs of these molecules are mainly contributed by benzo [ghi]perylene, which forms an orthogonal geometry with helicene moieties. The enantiomers of these molecules show opposite signals in CD and CPL spectra. The gabs and glum values could be increased with elongation of helicene structure. Compounds with [7]helicene moiety show relatively large gabs and glum values, which could reach up to 3.6 × 10−3 and 1.0 × 10−3, respectively. This work has provided a new strategy to develop chiral organic emitters through integration of benzo [ghi]perylene and helicene structures, which exhibit efficient fluorescent emission and intense CPL properties.