Tunable Natural and Magnetic Circularly Polarized Luminescence in the UVB Region from a Molecular Gd(III) Complex

Chiro-optical materials operating in the ultraviolet-B (UVB) region have the potential to enable transformative advances in asymmetric photocatalysis and covert security features. Nevertheless, molecular emitters with strong UVB circularly polarized luminescence (CPL) remain virtually nonexistent. We report a chiral Gd(III) complex that fills this gap with a tunable CPL at 312 nm. Molecular design takes advantage of a nonchromophoric chiral macrocyclic ligand promoting chiro-optical activity while avoiding competitive ligand absorption. The monomeric complex exhibits a sharp, high-quantum-yield emission (25%) with a CPL dissymmetry factor (glum) up to 0.019. This CPL signal is dramatically enhanced and modified upon controlled dimerization, yielding a 10-fold increase in glum. Furthermore, the system responds to magnetic fields, displaying unusually strong magnetic CPL (MCPL), which allows for the active modulation and reversal of the emergent polarization of the emission. The combination of high-energy emission, exceptional dissymmetry, and dual (chemical and magnetic) stimuli responsiveness positions these Gd(III) complexes at the forefront of emerging UV chiro-optical technologies.