Significance of Vibronic Coupling that Shapes Circularly Polarized Luminescence of Double Helicenes

This study investigates how molecular vibrations influence the circularly polarized luminescence (CPL) of double helicenes DPC and DNH. It highlights how structural changes during electronic transitions shape CPL spectra and dissymmetry (g) factor values, emphasizing the role of Herzberg-Teller effects in enhancing CPL responses.

Abstract

The circularly polarized luminescence (CPL) spectra of S- and X-shaped double helicenes exhibit distinct vibrational structures and overall shape variations. In this study, we conducted an in-depth investigation into the vibronic effects influencing the CPL spectra of two double helicenes, namely DPC and DNH. Employing state-of-the-art computations utilizing the FC-HT₁|VH model at the CAM−B3LYP/def2-TZVP level, we unveiled the paramount impact of Franck–Condon (FC), Herzberg-Teller (HT), and Duschinsky effects on their chiroptical responses. Our research underscores the pivotal role of structural deformations associated with the S₁-to-S₀ electronic transition in molding CPL spectra and wavelength-dependent dissymmetry (g) factor values, as well as the significance of HT effects in shaping and enhancing CPL responses. This extensive investigation not only advances our comprehension of the vibronic characteristics in configurationally distinct double helicenes but also offers valuable insights for the design of chiral molecules featuring controllable or finely-tunable CPL responses.

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