Achieving Circularly Polarized Luminescence and Two-Photon Excited Emission in Chiral Cofacial Naphthalenediimide-Based Crystalline Materials

Circularly polarized luminescence
and nonlinear optical
techniques
have garnered considerable attention due to their minimal energy loss
and superior optical penetration. However, there is still a lack of
mature strategies for designing materials that combine these two exceptional
optical properties. Herein, two chiral cofacial naphthalenediimide-based
crystals and their enantiomers (R-2NDI-1/S-2NDI-1 and R-2NDI-2/S-2NDI-2) feature yellowish-green
circular polarized luminescence emissions centered at ca. 525 and
550 nm, with the glum values as high as
±4.1 × 10–2 and ±6.1 × 10–2, as well as two-photon excited emissions centered
at 525 and 530 nm, with two-photon absorption cross-section values
at 770 nm up to 2.662 × 103 and 2.693 × 103 GM, respectively. Experimental results, theoretical calculations,
and crystal structure analysis demonstrate that the observed circularly
polarized luminescence and two-photon absorption arise from a synergistic
intramolecular and intermolecular electronic coupling effect. This
approach offers a promising strategy for the future development of
multifunctional crystalline optical materials.