Ring-Size Control and Guest-Induced Circularly Polarized Luminescence in Heteroleptic PdAB and PdAB Assemblies.

Two new structural motifs within the class of heteroleptic PdAB assemblies, namely syn-cis-PdAB bowls and bowl- (syn) or saddle- (anti) shaped cis-PdAB rings are introduced. All of the ten examples share a common longer fluorenone-based bis-monodentate ligand, equipped with meta-pyridine donor groups. The ring size (3- vs. 4-membered) and conformational preference (bowl vs. saddle) are controlled by the choice of the shorter ligand. These carry para-pyridine donors, different aromatic backbones (benzene, thiophene or selenophene) and either no or small or bulky endohedral substituents, serving to control the nuclearity of the heteroleptic rings through different effects (ligand angle, charge distribution or backbone bulk). Moreover, the luminescence of the fluorenone ligand is conserved in the formed architectures. Emission intensity as well as host-guest properties vary depending on the inward-pointing functions. All PdAB assemblies are shown to bind chiral guest BINOL bis-sulfonate which imparts its chirality to the entire host-guest complex. This results in a guest-induced circular dichroism (CD) and circularly polarized luminescence (CPL) with dissymmetry factor g up to 10.