Tuning Circular Dichroism and Circularly Polarised Luminescence in Single Crystals of a Perylene Diimide Macrocycle

Chiral materials that manipulate circularly polarised light have burgeoning applications across optoelectronics, sensing and information encoding, yet the functionality of organic molecular materials is often limited by their relatively low dissymmetry factors (g_abs/lum < 10^{- 2}), including towards the near infrared (λ > 700 nm). An effective strategy to amplifying g_abs/lum is to optimise the chiral arrangement of chromophores, with single crystals providing intrinsic molecular ordering. Herein, we quantify the circular dichroism and circularly polarised luminescence of single crystals of a chiral L-valinol bis-perylene diimide macrocycle by Mueller-Matrix polarimetry and circularly polarised luminescence microscopy, as required for the analysis of such anisotropic materials. Through this, we see that organic crystals are valuable for understanding how supramolecular structure can be used to modify the sign, strength and energy of the chiroptical signal. Indeed, by tuning the macrocycle's π-π stacking interactions, our materials deliver strong chiroptical properties (g_abs/lum > 10^{- 2}), including circularly polarised luminescence into the near infrared (λ = 780 nm).