Fig. 5: Ultrafast dynamics in the excited state.

a Transient absorption (TA) spectra of 1 (left), 2 (middle)33, and 3 (right) recorded in toluene. Positive and negative bands are highlighted in orange and pale orange, respectively. Signals denoted by asterisks are due to stimulated Raman scattering of solvent. b Schematic illustration of excited-state dynamics of π-extended helicenes and helicenes. The black, blue, and red arrows represent excitation, nonradiative decay, and radiative decay processes, respectively. c Franck–Condon (FC) and minimum energy conical intersection (MECI) geometries of π-extended [7]helicene 2 optimized using SF-ωB97XD/6-31G(d) level of theory.