Solvent-Directed Social Chiral Self-Sorting in PdL Coordination Cages.

A family of Pd cages prepared from ligands based on an axially chiral diamino-[1,1'-biazulene] motif (serving as a unique azulene-based surrogate of the ubiquitous BINOL moiety) is reported. We show that preparing a cage starting from the racemate of a shorter bis-monodentate ligand derivative, equipped with pyridine donor groups, leads to integrative ("social") chiral self-sorting, exclusively yielding the product, but only in a selection of solvents. This phenomenon is driven by individual solvent molecules acting as hydrogen bonding tethers between the amino groups of neighboring ligands, thereby locking the final coordination cage in a single isomeric form.

Interplay of Stereochemistry and Charge Governs Guest Binding in Flexible ZnL Cages.

Here, we report the synthesis of a family of chiral ZnL tetrahedral cages by subcomponent self-assembly. These cages contain a flexible trialdehyde subcomponent that allows them to adopt stereochemically distinct configurations. The incorporation of enantiopure 1-phenylethylamine produced Δ and Λ enantiopure cages, in contrast to the racemates that resulted from the incorporation of achiral 4-methoxyaniline.

Ligand Conformation Controls Assembly of a Helicate/Mesocate, Heteroleptic [PdLL'] Cages and a Six-Jagged [PdL] Ring.

Molecular building blocks, capable of adopting several strongly deviating conformations, are of particular interest in the development of stimuli-responsive self-assemblies. The pronounced structural flexibility of a short acridone-based bridging ligand, equipped with two monodentate isoquinoline donors, is herein exploited to assemble a surprisingly diverse series of coordination-driven Pd(II) architectures. First, it can form a highly twisted PdL helicate, transformable into the corresponding mesocate, controlled by temperature, counter anion and choice of solvent.

Guest-Induced Reversible Transformation between an Azulene-Based PdL Lantern-Shaped Cage and a PdL Tetrahedron.

Azulene, a blue structural isomer of naphthalene, is introduced as the backbone for a new family of Pd(II)-based self-assemblies. Three organic ligands, equipped with varying donor groups, produce three [PdL] cages of different cavity dimensions. Unexpectedly, the addition of organic disulfonate guests to the smallest lantern-shaped cage (featuring pyridine donors) led to a rapid and quantitative transformation to a distorted-tetrahedral [PdL] species.