Unravel Excited State Chirality Dynamics During Symmetry-Breaking Charge Separation
Symmetry-breaking charge separation (SB-CS) is a fundamental process in natural photosynthesis and holds promise for organic semiconductor applications. However, the influence of SB-CS on excited-state chirality has remained unexplored. Here, we employ femtosecond time-resolved circularly polarized luminescence (TRCPL) and transient absorption (TA) spectroscopy to investigate the excited-state chirality dynamics of a chiral perylenediimide bichromophore (Cy-PDI 2). Our results reveal that the locally excited (LE) state decays to a symmetry-breaking charge-separated (SB-CS) state within 88 ps in tetrahydrofuran (THF), while this process is strongly quenched in toluene (TOL). Time-dependent emission dissymmetry factor g_lum(t) extracted from TRCPL kinetics demonstrates a one-order-of-magnitude enhancement of circularly polarized luminescence after SB-CS, directly reflecting the asymmetry of electron cloud distribution on an ultrafast timescale. This work provides the first direct observation of excited-state chirality evolution during SB-CS and proposes a mechanistic framework. Our findings offer deeper insight into the origin of excited-state chirality, which is crucial for understanding efficient energy transfer, enantiospecific recognition, and asymmetric catalysis in biological and chemical systems.