Excited State Chirality Dynamics Revealed by Using Time-Resolved Circularly Polarized Luminescence Spectroscopy

The fundamental physics of the molecular excited state chirality refers to the breaking of time reversal symmetry of the electron density distribution in the excited states. Although steady-state circularly polarized luminescence (CPL) spectroscopy can measure the intensity difference between left- and right- circularly polarized emission, its time resolution limits the observation of excited state chirality generation and evolution, which accompany the excited state relaxation. It is envisaged that a combination of ultrafast time-resolved transient absorption and time-resolved circularly polarized luminescence (TRCPL) spectroscopy is a viable approach to achieve real-time observation of excited state chirality generation and evolution. In this concept, the technical principle and experimental setup of the recent developed femtosecond and nanosecond TRCPL spectroscopy instruments is presented. Additionally, examples are provided to showcase the utility of these techniques in the analysis of the excited state chirality origin and the mechanism of CPL enhancement by Föster resonance energy transfer.