Handedness-inverted polymorphic helical assembly and circularly polarized luminescence of chiral platinum complexes

Circularly polarized luminescence (CPL) materials have potential applications in three-dimensional (3D) displays, quantum encryption, and optical sensors. The development of single-component CPL materials with polymorphic assembly and handedness inversion remains a significant challenge. Herein, we present the access of such materials by controlling the underlying assembly pathway of well-designed chiral emitters. A pair of enantiomeric platinum complexes (R)-1 and (S)-1 decorated with a chiral α-methylbenzyl isocyanide ligand were prepared. By using the mixed-solvent (THF/n-hexane, THF=tetrahydrofuran) or high-concentration condition, these complexes were found to assemble via a cooperative or isodesmic pathway with significantly enhanced yellow or red emission, respectively. The aggregate samples obtained via these conditions show efficient CPL (dissymmery factor ∣glum∣>0.02, emission quantum yield Φ>20%). Interestingly, different assembly pathway leads to helical nanoribbons or nanofibers with opposite handedness from the complex with the same molecular chirality. This has been unambiguously and consistently manifested by circular dichroism and CPL spectral analysis and transmission electron, scanning electron, and atomic force microscope studies. This work demonstrates an appealing example of constructing polymorphic helical architectures with highly efficient CPL and inverted handedness thanks to the excellent assembly and emission of platinum complexes.