Formation of a Dimer of Trinuclear Helicates which Encapsulates an Array of Six Hydrogen-Bonded Anions

Spontaneous Resolution of Chiral Janus-Type Double-Layered Metallocyclic Strips Incorporating Möbius Ring and Circular Helicate

Homochiral metal-organic macrocyclic complexes are of great significance owing to their chirality and well-defined internal cavities that potentially have the ability to mimic complicated biological processes. Here we report a novel metal/anion-coordination co-driven strategy for the formation of nanoscale supramolecular metallocycles with unique topology, large size, and desired chirality. The enantiomeric Janus-type metallocyclic strips are assembled based on the synergistic coordination of sulfate anions and CoII ions to a bifunctional achiral ligand combining the o-phenylene-(bis)urea anion-chelating and 8-hydroxyquinoline metal-coordinating sites. The inherent chirality arises from two types of helical chiralities (triply twisted Möbius ring and circular helicate), which is observed for the first time for metal-organic complex systems. Notably, spontaneous chiral resolution by conglomerate crystallization into a pair of enantiomers (P- or M-Co9) is realized, which is attributed to the multiple weak intermolecular interactions facilitating the hierarchically helical superstructure.

Hexameric Lanthanide-Organic Capsules with Tertiary Structure and Emergent Functions

Biological macromolecules always function through a collective behavior of the aggregated constituents, which usually are self-assembled together via noncovalent interactions. Likewise, artificial supramolecular assemblies, whose properties and functions are mainly derived from their primary and secondary structures, may also aggregate into high-order architectures with emergent functions not available on the individual components. Here we report the first example of an insulin-like hexamerization of lanthanide triple helicates toward a 4 nm diameter hexameric capsule via consecutive metal-directed and anion-directed assembly processes. Hierarchical chiral-sorting self-assembly endows hexamers with aggregation-induced stability and emission enhancement. Furthermore, emergent guest-encapsulation function and enantioselectivity toward terpene drugs have been realized in the late-formed central cavity of the hexamers. This study not only provides a feasible strategy for constructing sophisticated and multifunctional lanthanide-organic materials but also sheds some light on the self-assembly processes in nature.

Self-Assembled Anion-Binding Cryptand for the Selective Liquid-Liquid Extraction of Phosphate Anions

The ligands L1 and L2 form trinuclear self-assembled complexes with Cu2+ (i.e. [(L1 )2 Cu3 ]6+ or [(L2 )2 Cu3 ]6+ ) both of which act as a host to a variety of anions. Inclusion of long aliphatic chains on these ligands allows the assemblies to extract anions from aqueous media into organic solvents. Phosphate can be removed from water efficiently and highly selectively, even in the presence of other anions.

Self-Assembly of an Anion-Binding Cryptand for the Selective Encapsulation, Sequestration, and Precipitation of Phosphate from Aqueous Systems

The self-assembled trimetallic species [L₂ Cu₃ ]⁶⁺ contains a cavity that acts as a host to many different anions. By using X-ray crystallography, ESI-MS, and UV/Vis spectroscopy we show that these anions are encapsulated both in the solid state and aqueous systems. Upon encapsulation, the anions Br^- , I^- , CO₃^2- , SiF₆^2- , IO₆^3- , VO₄^3- , WO₄^2- , CrO₄^2- , SO₄^2- , AsO₄^3- , and PO₄^3- are all precipitated from aqueous solution and can be removed by filtration. Furthermore, the cavity can be tuned to be selective to either phosphate or sulfate anions by variation of the pH. Phosphate anions can be removed from water, even in the presence of other common anions, reducing the concentration from 1000 to <0.1 ppm and recovering approximately 99 % of the phosphate anions.

Dihydrogen phosphate-containing dinuclear double assemblies that demonstrate phosphate reactivity to the tetrafluoroborate anion

The ligands L1 and L2 both form dinuclear assemblies with Cu(ii) and these react with dihydrogen phosphate so that the anion is incorporated within the assembly (e.g. [Cu2L2(H2PO4)]3+). However, in the presence of tetrafluoroborate anions the phosphate undergoes reaction with the anion forming [Cu3(L1)3(O3POBF3)]3+ and [Cu2(L2)2(O2P(OBF3)2)]+.

Self-assembly of rare octanuclear quad(double-stranded) cluster helicates showing slow magnetic relaxation and the magnetocaloric effect

Four rare structurally novel octanuclear quad(double-strands) cluster helicates containing Ln8 polyhedron cores have been synthesized. Magnetic studies show that the Gd derivative exhibits the magnetocaloric effect and the Dy derivative shows slow magnetic relaxation under zero dc field.

Anion-coordination-directed self-assemblies

This review introduces the interplay of anion coordination and supramolecular self-assembly, presenting recent progress in anion-induced and anion-coordination-based self-assemblies.

A folded [2 × 2] metallo-supramolecular grid from a bis-tridentate (1,2,3-triazol-4-yl)-picolinamide (tzpa) ligand

A flexible ditopic ligand 1 containing two N,N,O-tridentate (1,2,3-triazol-4-yl)-picolinamide chelating pockets is reported and the formation of multimetallic architectures is explored in the solid and the solution phase. The self-assembled Zn^II complex [Zn₄(1)₄](ClO₄)₈ exhibited a folded [2 × 2] square grid supramolecular architecture that selectively assembled in MeCN solution as shown using various spectroscopic techniques. The closely related Fe^II complex shows equivalent behaviour in the solid state, while a discrete dinuclear species [Cu₂(NO₃)₄1]·5MeCN was the sole product observed in the solid state from the reaction between 1 and Cu^II under similar conditions.