Post-Assembly Polymerization of Discrete Anion-Coordinated Triple Helicate.

Hierarchical self-assembly has been recently employed in the construction of anion-coordination-driven gel materials. However, the post-assembly modification strategy, which may be a highly efficient strategy to realize the functionalization of discrete 'aniono' supramolecular architectures, has not been employed yet. Herein we report the first example of anion-coordination-driven gel material cross-linked by well-defined 'aniono' triple helicate through post-assembly polymerization. The obtained gel shows self-healing property and excellent compatibility with various surfaces, including glass, rubber, leaf, PP, and metal. The viscoelastic gel constructed through the post-assembly modification strategy enriches the method to construct the anion-coordination-driven smart materials.

Humidity-Induced Self-Oscillating and Self-Healing Hypercrosslinked Metal-Organic Polyhedra Membranes.

Designing autonomously oscillating materials is highly desirable for emerging smart material fields but challenging. Herein, a type of hypercrosslinked metal-organic polyhedra (HCMOPs) membranes formed by covalent crosslinking of boronic acid-modified Zr-based MOPs with polyvinyl alcohol (PVA) are rationally designed. In these membranes, MOPs serve as high-connectivity nodes and provide dynamic borate bonds with PVA in hypercrosslinked networks, which can be broken/formed reversibly upon the stimulus of water vapor. The humidity response characteristic of HCMOPs promotes their self-oscillating and self-healing properties. HCMOP membranes can realize a self-oscillating property above the water surface even after loading a cargo that is 1.5 times the weight of the membrane due to the fast adsorption and desorption kinetics. Finally, the HCMOP actuator can realize energy conversion from mechanical energy into electricity when coupled with a piezoelectric membrane. This work not only paves a new avenue to construct MOP-polymer hybrid materials but also expands the application scopes of MOPs for smart actuation devices.

Post-Assembly Modification of Homochiral Titanium-Organic Cages for Recognition and Separation of Molecular Isomers.

A chiral metal-organic cage (MOC) was extended and fixed into a porous framework using a post-assembly modification strategy, which made it easier to study the host-guest chemistry of the solid-state MOC using a single-crystal diffraction technique. Anionic Ti4 L6 (L=embonate) cage can be used as a 4-connecting crystal engineering tecton, and its optical resolution was achieved, thus homochiral ΔΔΔΔ- and ΛΛΛΛ-[Ti4 L6 ] cages were obtained. Accordingly, a pair of homochiral cage-based microporous frameworks (PTC-236(Δ) and PTC-236(Λ)) were easily prepared by a post-assembly reaction. PTC-236 has rich recognition sites provided by the Ti4 L6 moieties, chiral channels and high framework stability, affording a single-crystal-to-single-crystal transformation for guest structure analyses. Thus it was successfully utilized for the recognition and separation of isomeric molecules. This study provides a new approach for the orderly combination of well-defined MOCs into functional porous frameworks.

Self-Healing and Shape Memory Hypercrosslinked Metal-Organic Polyhedra Polymers via Coordination Post-Assembly.

Coordination-driven crosslinking networks with reversible and dynamic characteristics are gaining increasing interest in diverse application fields. Herein, we use a coordination crosslinking approach using metal-organic polyhedra (MOPs) as high-connectivity building blocks to post-assemble a class of coordination hypercrosslinked MOP (CHMOP) polymers. The introduction of 12-connected MOP nodes to the polymeric networks is critical to producing membranes that overcome the trade-off between mechanical properties and dynamic healing, and meanwhile possess multifunctionalities including shape memory, solution processability, and 3D printing. The CHMOPs can also be used for anticorrosion coating and achieve function couplings, e.g., shape memory-assisted self-healing (SMASH), which have not been achieved in the MOP-based hybrid materials yet. This work not only offers a feasible strategy to construct new multifunctional materials but also greatly expands the application scopes of MOPs.

Formation of Supramolecular Nanostructures through in Situ Self-Assembly and Post-Assembly Modification of a Biocatalytically Constructed Dipeptide Hydrazide.

Aqueous self-assembly of short peptides has attracted growing attention for the construction of supramolecular materials for various bioapplications. Herein, we describe how the thermolysin-assisted biocatalytic construction of a dipeptide hydrazide from an N-protected amino acid and an amino acid hydrazide leads to the formation of thermally stable supramolecular hydrogels. In addition, we demonstrate the post-assembly modification of the supramolecular architectures constructed in situ tethering hydrazide groups as a chemical handle by means of fluorescence imaging.

Post-Assembly Reactivity of N-Aryl Iminoboronates: Reversible Radical Coupling and Unusual B-N Dynamic Covalent Chemistry.

Post-assembly reaction of a dynamic covalent iminoboronate system following addition of Cp2 Co resulted in the formation of a series of new reductively coupled dianionic dimers via C-C bond formation. The dimers formed as a mixture of BN-containing isomeric products: diastereomers rac5 and meso5, with coupled five-membered rings, and enantiomeric rac6, with a fused six-membered ring bicyclic system from C-C bond formation and rearrangement of the B-N bonds. Each isomer was identified using 1 H NMR spectroscopy in combination with single crystal X-ray structure determination. Interestingly, interconversion between the coupled five-membered rings (rac5 ) and fused bicyclic systems (rac6 ) was found to occur through an unprecedented breaking and reforming of the B-N covalent bond. Further, the coupled products could be converted quantitatively back to their iminoboronate precursors with addition of the electron abstractor Ph3 C+ .

Metal Organic Polyhedra: A Click-and-Clack Approach Toward Targeted Delivery.

Mixed self-assembly of ligands 1 and 2, PXDA (3), and Pd(NO3)2 afforded metal organic polyhedra (MOP 1 - MOP 3) which bear 24 covalently attached CB[7] and cyclooctyne moieties. Post assembly modification (PAM) of MOP 3 by covalent strain promoted alkyne azide click reaction provided MOP 4 R bearing covalently attached functionality (PEG, sulfonate, biotin, c-RGD, fluorescein and cyanine). Orthogonal CB[7] guest mediated non-covalent PAM of MOP 4 R with Ad-FITC afforded MOP 5 RGD Ad-FITC and MOP 5 biotin 0020Ad-FITC. Flow cytometry analysis of the uptake of MOP 5 RGD Ad-FITC toward U87 cells demonstrated improved uptake relative to control MOP lacking c-RGD ligands. These results suggest a broad applicability of orthogonally functionalizable (covalent and non-covalent) MOPs in targeted drug delivery and imaging applications.

A Microgripper with a Post-Assembly Self-Locking Mechanism.

In this work, we report a new design for an electrostatically actuated microgripper with a post-assembly self-locking mechanism. The microgripper arms are driven by rotary comb actuators, enabling the microgripper to grip objects of any size from 0 to 100 µm. The post-assembly mechanism is driven by elastic deformation energy and static electricity to produce self-locking and releasing actions. The mechanism enables the microgripper arms to grip for long periods without continuously applying the external driving signal, which significantly reduces the effects and damage to the gripped objects caused by these external driving signals. The microgripper was fabricated using a Silicon-On-Insulator (SOI) wafer with a 30 µm structural layer. Test results show that this gripper achieves a displacement of 100 µm with a driving voltage of 33 V, and a metal wire with a diameter of about 1.6 mil is successfully gripped to demonstrate the feasibility of this post-assembly self-locking mechanism.

Synthesis of a trisaccharide repeat of the zwitterionic Sp1 capsular polysaccharide utilizing 2-Azido-4-benzylamino-4N,3-O-carbonyl-2,4,6-trideoxy-d-galactopyranosyl trichloroacetimidate.

2-Azido-4-benzylamino-4N,3-O-carbonyl-2,4,6-trideoxy-d-galactopyranosyl trichloroacetimidate 2 conveniently prepared in six steps from 6-deoxy-d-glucal glycosylated a selectively protected α1,3 linked methyl galabioside to afford the trisaccharide skeleton of a repeating unit of the Sp1 zwitterionic capsular polysaccharide. Lithium hydroxide hydrolysis of the 3,4-cyclic carbamate permitted the creation of a 2-acetamido-4-amino-2,4,6-trideoxygalactose residue. Selective cleavage of p-methoxybenzyl ethers by trifluoroacetic acid gave a selectively deprotected trisaccharide with two hydroxymethyl groups that were oxidized by the TEMPO reagent to afford access to trisaccharide glycoside 1 containing 2-acetamido-4-amino-2,4,6-trideoxygalactose and two galacturonic acid residues.