Ring‐Size Control and Guest‐Induced Circularly Polarized Luminescence in Heteroleptic Pd3A3B3 and Pd4A4B4 Assemblies

• Published in: Angewandte Chemie Vol. 136; no. 46
• Main Authors: Ebbert, Kristina E., Benchimol, Elie, Platzek, André, Drechsler, Christoph, Openy, Joseph, Hasegawa, Shota, Holstein, Julian J., Clever, Guido H.
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 11-11-2024
• Subjects: Assemblies; Benzene; cages; Charge distribution; Chirality; Circular dichroism; Circular polarization; CPL; Dichroism; host–guest chemistry; Ligands; Luminescence; Pyridines; self-assembly; Supramolecular compounds
• ISSN: 0044-8249; 1521-3757
• DOI: 10.1002/ange.202413323

Two new structural motifs within the class of heteroleptic PdnAnBn assemblies, namely syn‐cis‐Pd3A3B3 bowls and bowl‐ (syn) or saddle‐ (anti) shaped cis‐Pd4A4B4 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 Pd3A3B3 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 glum up to 10−3.
Non‐statistical multicomponent assembly gives simple synthetic access to the first Pd3A3B3 bowls, capable of showing guest‐induced circularly polarized luminescence (CPL). Adjustment of ligand angle or backbone functionality allows control over the ring size, yielding Pd4A4B4 bowls or saddle‐type structures.