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Cucurbituril-Based Molecular Recognition.

Hydrogen-bonded organic frameworks (HOFs) represent an interesting type of polymeric porous materials that can be self-assembled through H-bonding between organic linkers. To realize permanent porosity in HOFs, stable and robust open frameworks can be constructed by judicious selection of rigid molecular building blocks and hydrogen-bonded units with strong H-bonding interactions, in which the framework stability might be further enhanced through framework interpenetration and other types of weak intermolecular interactions such as π⋯π interactions. Owing to the reversible and flexible nature of H-bonding connections, HOFs show high crystallinity, solution processability, easy healing and purification. These unique advantages enable HOFs to be used as a highly versatile platform for exploring multifunctional porous materials. Here, the bright potential of HOF materials as multifunctional materials is highlighted in some of the most important applications for gas storage and separation, molecular recognition, electric and optical materials, chemical sensing, catalysis, and biomedicine.

Multifunctional porous hydrogen-bonded organic framework materials.

We demonstrate an aqueous organic and organometallic redox flow battery utilizing reactants composed of only earth-abundant elements and operating at neutral pH. The positive electrolyte contains bis((3-trimethylammonio)propyl)ferrocene dichloride, and the negative electrolyte contains bis(3-trimethylammonio)propyl viologen tetrachloride; these are separated by an anion-conducting membrane passing chloride ions. Bis(trimethylammoniopropyl) functionalization leads to ∼2 M solubility for both reactants, suppresses higher-order chemical decomposition pathways, and reduces reactant crossover rates through the membrane. Unprecedented cycling stability was achieved with capacity retention of 99.9943%/cycle and 99.90%/day at a 1.3 M reactant concentration, increasing to 99.9989%/cycle and 99.967%/day at 0.75–1.00 M; these represent the highest capacity retention rates reported to date versus time and versus cycle number. We discuss opportunities for future performance improvement, including chemical modification...

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A Neutral pH Aqueous Organic–Organometallic Redox Flow Battery with Extremely High Capacity Retention

Host–guest chemistry in two-dimensional supramolecular networks

Self-assembly of ligand 1 and Pd(NO3)2 delivers Fujita-type metal–organic polyhedron (MOP) 3 which bears 24 covalently attached methyl viologen units on its external surface, as evidenced by 1H NMR, diffusion-ordered spectroscopy NMR, electrospray mass spectrometry, transmission electron microscopy, and atomic force microscopy measurements. MOP 3 undergoes noncovalent complexation with cucurbit[n]urils to yield MOPs 4–6 with diameter ≈5–6 nm. MOP 5 can be fully loaded with doxorubicin (DOX) prodrug 2 via hetero–ternary complex formation to yield 7. The MOPs exhibit excellent stability toward neutral to slightly acidic pH in 10 mM sodium phosphate buffer, mitigating the concern of disassembly during circulation. The results of MTS assays show that MOP 7 is 10-fold more cytotoxic toward HeLa cells than equimolar quantities of DOX prodrug 2. The enhanced cytotoxicity can be traced to a combination of enhanced cellular uptake of 7 and DOX release as demonstrated by flow cytometry and confocal fluorescence mic...

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Metal-Organic Polyhedron Capped with Cucurbit[8]uril Delivers Doxorubicin to Cancer Cells

Supramolecular organic frameworks: engineering periodicity in water through host–guest chemistry

Aromatic stacking has played a significant role in the design of discrete supramolecular systems. However, for many years, the stacking of conjugated radical cations has been considered only as a novelty due to its weakness. In recent years, it has been demonstrated that the stacking of conjugated radical cations, particularly those formed by bipyridinium or tetrathiafulvalene, can be enhanced remarkably when they are incorporated into rationally designed, preorganized frameworks or entrapped into a confined space. This Focus Review highlights the recent advance in its application as an emerging non-covalent force for the construction of various supramolecular structures.

Dimerization of conjugated radical cations: An emerging non-covalent interaction for self-assembly

Two dynamic covalent polymers P1 and P2 were prepared by alternately linking electron-rich tetrathiafulvalene (TTF) and electron-deficient bipyridinium (BIPY2+) through hydrazone bonds. In acetonitrile, the polymers were induced by intramolecular donor–acceptor interactions to form pleated foldamers, which unfolded upon oxidation of the TTF units to the radical cation TTF.+. Reduction of the BIPY2+ units to BIPY.+ led to the formation of another kind of pleated secondary structures, which are stabilized by intramolecular dimerization of the BIPY.+ units. The diradical dicationic cyclophane cyclobis(paraquat-p-phenylene) (CBPQT2(.+)) could further force the folded structures to unfold by including the BIPY.+ units of the polymers. Upon oxidation of the BIPY.+ units of the cyclophane and polymers to BIPY2+, the first folded state was regenerated. Switching or conversion between the four conformational states was confirmed by UV/Vis spectroscopic experiments.

Quadruple switching of pleated foldamers of tetrathiafulvalene-bipyridinium alternating dynamic covalent polymers.

Conjugated radical cation dimerization-driven generation of supramolecular architectures

Synthesis and characterization of trans-Pt(II)(salicylaldimine)(pyridine/pyridine-4-carbinol)Cl complexes: In vivo inhibition of E. coli growth and in vitro anticancer activities

Lan Chen

Papers

Supramolecular organic frameworks: engineering periodicity in water through host–guest chemistry

Dimerization of conjugated radical cations: An emerging non-covalent interaction for self-assembly

Quadruple switching of pleated foldamers of tetrathiafulvalene-bipyridinium alternating dynamic covalent polymers.

Conjugated radical cation dimerization-driven generation of supramolecular architectures

Synthesis and characterization of trans-Pt(II)(salicylaldimine)(pyridine/pyridine-4-carbinol)Cl complexes: In vivo inhibition of E. coli growth and in vitro anticancer activities