Circularly polarized luminescence: from spectroscopy to applications

Chiral molecules can emit left and right polarized light with different intensities; this phenomenon is known as circularly polarized luminescence (CPL). CPL can be observed in photoluminescence and in electroluminescence. In general CPL spectroscopy can be an interesting tool to investigate the chirality of the excited state or it can be employed in technological applications such as OLEDs able to directly emit circularly polarized electroluminescence (CP-OLEDs). The first part of this work concerns chiral lanthanide complexes, which can emit CPL with a degree of circular polarization which is almost precluded to non- aggregated purely organic molecules. In this part, we present a new chiral Eu complex with highly polarized emission and, a series of CP-OLEDs based on a lanthanide complex. Following this strategy, the highest polarization degree reported to date is obtained. Moreover, we discuss and rationalize the factors affecting the polarization inside a device. In the second part, we investigate the CPL properties of chiral organic molecules and we apply CPL spectroscopy as a qualitative analytical tool in pH-dependent chiroptical switch and to signal the interaction between fluorescent stains and protein-based matrices used in paintings.