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

Abstract

Metallosupramolecule-based polymeric platforms with high degrees of hierarchy and tailorable functionalities are of great interests because of their unique morphologies and potential applications. Herein, the controllable synthesis of a highly-ordered polymeric structure, {[M,P-Co (PDA) (HIP) (DMF) (H O)] -[Co(DMF)(H O) ]} (1) (PDA=2,6-pyridinedicarboxylate, HIP=5-hydroxyisophthalate, DMF=dimethylformamide) with unique topology is reported. The solid-state structure of 1 reveals that it is alternately and periodically assembled from racemic supramolecular monomers to form a zigzag-shaped polymeric strand. Discrete racemic supramolecules (2) with topologies similar to those of monomeric species of 1 are also controllably synthesized in a separate reaction. Formation of intermolecular hydrogen bonds between supramolecules associated with hydroxyl groups of HIPs are critical for the unique solid-state packing geometries of 1 and 2.

Heteroleptic Triple-Stranded Metallosupramolecules with Hydrophobic Inner Voids

“…Note that the coordinated solvents in terminal nickels may not be the same in every experiment. The metal clusters possess chirality, either clockwise or counterclockwise, which is similar to the reported structures. − Each discrete supramolecule of 1 is constructed from two metal clusters with opposite chirality, resulting in a meso-helicate (Figure ). The existence of one mirror plane of symmetry passing through the middle point of the three CH 3 -TP ligands initiates C 3h symmetry of the meso-helicate.…”

“…The inner empty space of 1 , as illustrated in Figure S9, is noticeable. The size of this “inner cage” is significantly larger than the similar empty spaces of the previously reported triple-stranded supramolecules prepared using PTA or CDBA ligands. − The larger size of the inner space of 1 possibly allows the inclusion of external molecules through further ligand modification. In general, the hydrophobicity of a cage can be proved by the inclusion of hydrophobic molecules from the water phase .…”

“…The existence of one mirror plane of symmetry passing through the middle point of the three CH 3 -TP ligands initiates C 3h symmetry of the meso-helicate. This is unique when compared to the reported triple-stranded supramolecules, − which show two metal clusters of the same chirality interconnected via three PTA derivative or CDBA bridging ligands, leading to the formation of either right-handed or left-handed helicate with C 3 symmetry. In terms of crystal packing, the discrete molecules of 1 are arranged regularly into layers.…”

“…CH 3 -H 2 TP (5′-methyl-[1,1′:3′,1′′-terphenyl]-4,4′′-dicarboxylic acid) and HO-H 2 TP (5′-hydroxy-[1,1′:3′,1′′-terphenyl]-4,4′′-dicarboxylic acid) were synthesized through a Suzuki coupling reaction according to the method reported in the literature with a slight modification. − Similar to H 2 PTA (benzene-1,3-dicarboxylic acid) and H 2 CDBA (4,4′-carbonyl­dibenzoic acid) used in the syntheses of the previously reported triple-stranded supramolecules, − both CH 3 -H 2 TP and HO-H 2 TP are ditopic ligands with a bending angle of ∼120° (Scheme ). The fundamental difference between substituted H 2 TP ligands and H 2 PTA or H 2 CDBA lies in their length and flexibility, that is, the distance between the carbon atoms in the two carboxyl groups of H 2 TP ligand is significantly longer than those of H 2 PTA and H 2 CDBA (Scheme ).…”

“…In our reported works, we have reported a range of supramolecules in which metal ions (Co 2+ , Ni 2+ , or Mn 2+ ) coordinated with 2,6-pyridine­dicarboxylate (PDA) to form tetranuclear metal clusters (primary assembly), and two metal clusters are interlinked by three bridging ligands, that is, benzene-1,3-dicarboxylate (PTA) derivatives or 4,4′-carbonyl­dibenzoate (CDBA), to form triple-stranded helicates (TSH) with C 3 symmetry. − For supramolecules constructed from PTA derivative, three bridging ligands with a bending angle of 120° create an empty space within the supramolecule. Depending on the substituent/functional group attached to C5 of the PTA ligand, various higher-order assembly modes were obtained such as discrete, polymeric, and cage metallo­supramolecules. − When moving from a one-benzene ring system (PTA) to a two-benzene ring system (CDBA), TSHs could also be obtained with C 3 symmetry . The inner voids surrounded by three CDBA ligands are larger than those surrounded by three PTA derivative ligands.…”