A Cobalt Supramolecular Triple-Stranded Helicate-based Discrete Molecular Cage

Abstract

We report a strategy to achieve a discrete cage molecule featuring a high level of structural hierarchy through a multiple-assembly process. A cobalt (Co) supramolecular triple-stranded helicate (Co-TSH)-based discrete molecular cage (1) is successfully synthesized and fully characterized. The solid-state structure of 1 shows that it is composed of six triple-stranded helicates interconnected by four linking cobalt species. This is an unusual example of a highly symmetric cage architecture resulting from the coordination-driven assembly of metallosupramolecular modules. The molecular cage 1 shows much higher CO2 uptake properties and selectivity compared with the separate supramolecular modules (Co-TSH, complex 2) and other molecular platforms.

Metal‐Ion Tuning in Triple‐Stranded Helicate‐Based Metallosupramolecules

“…The helical conformation of these structures essentially results from the interconnection of tetranuclear cobalt clusters, which are formed by cobalt ions and PDA ligands, through three PTA ligands. For structural analysis of the related structures, multilevel coordination‐driven assembly has been proposed to systematically classify their structural hierarchy . Deliberate variation of PTA derivatives has also been attempted; however, supramolecules with similar helical geometry are always obtained, suggesting that the helical structure could be the key point in drawing the assembly of these heteroleptic supramolecules.…”

“…For structural analysis of the related structures, multilevel coordination‐driven assembly has been proposed to systematically classify their structural hierarchy . Deliberate variation of PTA derivatives has also been attempted; however, supramolecules with similar helical geometry are always obtained, suggesting that the helical structure could be the key point in drawing the assembly of these heteroleptic supramolecules. These experimental observations are one of the essential motivations to further examine the generation of such heteroleptic helicates by varying the transition‐metal ions.…”

Controllable Synthesis of a Highly Ordered Polymeric Structure Assembled from Cobalt‐Cluster‐based Racemic Supramolecules

“…Discrete or polymeric assemblies involved the use of predefined, well‐organized supramolecules as basic monomers often exhibit structural diversity, symmetry, and complexity –. To clarify the related structures, we have employed the multilevel assembly concept to classify the structures based on their respective hierarchical levels . Basically, the multilevel assembly is composed of (i) primary, (ii) secondary, (iii) tertiary, or higher‐order assembly.…”

“…Basically, the multilevel assembly is composed of (i) primary, (ii) secondary, (iii) tertiary, or higher‐order assembly. Based on the concept, our group has demonstrated a variety of supramolecular assemblies, in which four cobalt atoms are coordinated by three 2,6‐pyridinedicarboxylate ligands, forming a non‐isolable tetranuclear cobalt cluster as a primary assembly unit with three extension points . Bent ditopic isophthalate ligands or their derivatives (e.g.…”

“…5‐ tert ‐butyl isophthalate) interlink two primary assembly units to form a secondary supramolecular structure. More importantly, the presence of unsaturated and outwardly oriented carboxylate oxygen donors on the secondary supramolecular structures coupled with appropriate coordination spheres of cobalt make them suitable for the construction of tertiary‐assembled hierarchical platforms possessing target‐oriented properties that can rarely be obtained in individual units . In addition, host‐guest interactions between supramolecules can lead to a unique crystal packing platforms with a structural hierarchy .…”