Controllable Coordination Self‐Assembly Based on Flexibility of Ligands: Synthesis of Supramolecular Assemblies and Stimuli‐Driven Structural Transformations

Amplification of weak chiral inductions for excellent control over the helical orientation of discrete topologically chiral (M3L2) n polyhedra

Superb control over the helical chirality of discrete (M₃L₂)_n polyhedra (n = 2,4,8, M = Cu^I or Ag^I) created from the self-assembly of propeller-shaped ligands (L) equipped with chiral side chains is demonstrated here. Almost perfect chiral induction (>99 : 1) of the helical orientation of the framework was achieved for the largest (M₃L₂)₈ cube with 48 small chiral side chains (diameter: ∼5 nm), while no or moderate chiral induction was observed for smaller polyhedra (n = 2, 4). Thus, amplification of the weak chiral inductions of each ligand unit is an efficient way to control the chirality of large discrete nanostructures with high structural complexity.

Superb control over the helical chirality of highly-entangled (M₃L₂)_n polyhedra (M = Cu(i), Ag(i); n = 2,4,8) was achieved via multiplication of weak chiral inductions by side chains accumulated on the huge polyhedral surfaces.

Flexible Vertex Engineers the Controlled Assembly of Distorted Supramolecular Tetrahedral and Octahedral Cages

Designing and building unique cage assemblies attract increasing interest from supramolecular chemists but remain synthetically challenging. Herein, we propose the use of a flexible vertex with adjustable angles to selectively form highly distorted tetrahedral and octahedral cages, for the first time, in which the flexible vertex forms from the synergistic effect of coordination and covalent interactions. The inherent interligand angle of the vertex can be modulated by guest anions present, which allows for the fine-tuning of different cage geometries. Furthermore, the reversible structural transformation between tetrahedral and octahedral cages was achieved by anion exchange monitored by mass spectrometric technique, the smaller anions favoring tetrahedral cages, while the larger anions supporting octahedral cages. Additionally, the KBr-based cage thin films exhibited prominent enhancement of their third-order NLO responses in two or three orders of magnitude compared to those obtained for their corresponding solutions. This work not only provides a new methodology to build irregular polyhedral structures in a controlled and tunable way but also provides access to new kinds of promising functional optical materials.

Comparison of [Pd2L4][BF4]4 cages for binding of n-octyl glycosides and nitrate (L = isophthalamide or dipicolinamide linked dipyridyl ligand)

Two dipyridyl ligands were synthesized, where the pyridyl donor fragments were separated by an isophthalamide (1) or a dipicolinamide moiety (2). Both ligands formed [Pd2(Ligand)4][BF4]4 complexes in CD2Cl2 containing 5% dmso-d6. It was found that while [Pd2(1)4][BF4]4 readily binds to n-octyl glycosides and to nitrate anions, [Pd2(2)4][BF4]4 did not. The difference in binding properties could be rationalized based on the reduced flexibility and size of the [Pd2(2)4]2+ cage and/or stronger interior binding of a BF4- counter anion.

Customized self-assembled molecules: rim adjustable coronal polygons with multiple-folds symmetry

Three desired discrete metallomacrocyclic wreaths with four-, five- and six-fold symmetry were successfully realized in a controlled fashion.