Intrinsically Chiral Excimers: Water-Compatible Trityl-Based Nanoparticles as Tailored Dual Emitters of Circularly Polarized Luminescence in the Vis or NIR Regions.

Circularly polarized light is characterized by the rotation of theelectric field vector in a clockwise or counterclockwise direction as it propagates, enabling the transmission of information through two independent channels. This property facilitates advances in communication technologies, sensing, bioimaging, and medical diagnostics. However, its efficient generation remains challenging due to energy losses inherent to conventional filter-based methods. Chiral molecules, like metal-free halogenated trityl radicals, can directly convert unpolarized light into circularly polarized one, thanks to the different chiroptical properties of their two propeller-like enantiomers, which arise from the opposite torsion of their aromatic rings. These systems pioneered the emission of chiral light from purely organic radicals, opening new avenues for multifunctional molecular platforms. Moreover, they can be nanostructured into water-compatible organic nanoparticles (ONPs), promoting the formation of red-shifted excimer emission approaching the near-infrared (NIR) biological window. This work demonstrates a dual circularly polarized luminescence (CPL) in aqueous environments from chiral ONPs using the enantiomeric forms of a brominated trityl derivative (TTBrM) embedded within their non-radical precursor (TTBrM-αH). By tailoring the radical content, two distinct chiral emissions ─monomeric and excimeric─ are achieved within the same nanostructured platform. These findings position chiral trityl-based ONPs as efficient and biocompatible CPL emitters with strong potential for future applications in optical and biomedical technologies.