π-Aggregation-Free, Fused Perylene Pentamers: Synthesis, Narrowband Far-Red to Near-Infrared Emission, and Chiroptical Properties

Abstract

Chiral nanographenes have emerged as promising materials for chiral optoelectronics owing to their intrinsic chiroptical properties. However, their development remains constrained by synthetic challenges, strong π–aggregation, and low fluorescence quantum yields, while emission extending to the near-infrared (NIR) region is still rare. Here, we present a molecular design strategy that combines structural multiplicity with π-extension in a butterfly-shaped fused perylene pentamer scaffold to achieve active circularly polarized luminescence (CPL) emitters. By tuning the Scholl reaction conditions, we selectively obtained either racemic 1a (1a-rac) together with its meso-isomer (1a-meso) or an extended series of nanographenes (1a–1d). X-ray crystallography revealed contorted architectures featuring helicene subunits, while bulky aryl substituents improved solubility, enhanced stability, and enabled enantiomer separation. Owing to their extended π-conjugation, perylene-like frontier orbital distribution, and increased molecular symmetry and rigidity, these nanographenes exhibit highly tunable and remarkable optical and chiroptical properties. Notably, 1a demonstrates outstanding chiroptical performance (ΦF = 65%, BCPL = 66.7 M⁻¹ cm⁻¹), whereas 1d exhibits narrowband emission (FWHM = 37 nm) spanning the far-red to near-infrared region.