Modular enhancement of circularly polarized luminescence in Pd 2 A 2 B 2 heteroleptic cages.

Metal-mediated assembly allows us to combine an achiral emissive ligand A with different chiral ligands (such as B) in a non-statistical fashion, obtaining Pd 2 A 2 B 2 heteroleptic cages showing circularly polarized luminescence (CPL). By using the 'shape complementary assembly' (SCA) strategy, the cages are exclusively obtained as cis -Pd 2 A 2 B 2 stereoisomers, as confirmed by NMR, MS and DFT analyses. Their unique chiroptical properties derive from the synergy of all the building blocks. Ligand B imparts the chiral information of its aliphatic backbone, comprising two stereogenic sp 3 carbon centres, to the overall structure, causing CD and CPL signal induction for the chromophore on ligand A. The heteroleptic cage shows CPL with a | g lum | value of 2.5 × 10 -3 , which is 3-times higher than that for a progenitor based on aromatic helical building block H, thus opening a rational route towards optimizing the CPL properties of self-assembled nanostructures in a modular way.