LAUSR

Circularly polarized luminescence (CPL) discloses rich information about molecular chirality in the excited state. The number of reports on CPL studies has increased significantly since 2010: with the progress of instrumental techniques and calculation methods, CPL is widely used in the development of smart materials for advanced photonic technologies, 3D display and bio-responsive studies. Recently, several significant overviews have been presented on CPL instrumental development and theoretical interpretation (Longhi et al., 2016), CPL of lanthanide complexes (Zinna and Di Bari, 2015), small organic molecules (Sanchez-Carnerero et al., 2015; Mori, 2020) and supramolecular assemblies (Kumar et al., 2015). A key factor to evaluate the enhancement of CPL is the dissymmetry factor glum. A general theoretical aspect to achieve high value of the glum is the manipulation of optical transitions with strong magnetic and weak electric dipole transition moment contribution. This Special Issue includes 12 contributions (1 Perspective, 2 Reviews, 3 mini-reviews, and 6 research papers) that touch experimental and theoretical aspects of CPL enhancement studies, including small organic molecules, polymers, aggregates, and metal complexes. In a perspective paper, Kondo et al. summarize the KBr pellet method for CPL measurement, providing a protocol for solid-state CPL measurement and temperature-dependent samples. Doistau et al. discuss the strategies to obtain strong CPL activity, and compare optical properties of CPL materials based on chiral d-block and f-block metal complexes, demonstrating an empirical protocol for CPL applications with cheap transitional metals. Gao et al. review the most recent advances in switchable CPL aspects toward external stimuli, giving an overview of CPL switches for various technical applications. Nagata and Mori present a specific mini-review on simultaneous improvement of luminescence quantum yields and dissymmetry factors, paving a way for obtaining excellent organic CPLmaterials. A special focus on cyclophane-based chromophore in CPL materials is reported in the minireview by Sugiura. Upon synthetic chemical tools, one may manipulate the orientations of fluorophores and obtain strong CPL materials as desired. In the mini-review by Kumar et al., they discuss several chiral templates such as liquid crystals, biomolecules, molecular self-assemblies and chiral gelators utilized for generating enhanced CPL in organic luminophores. Edited and reviewed by: Doo Soo Chung, Seoul National University, South Korea