The Role of Torsional Dynamics on Hole and Exciton Stabilization in π‐Stacked Assemblies: Design of Rigid Torsionomers of a Cofacial Bifluorene

Exciton and charge delocalization across π‐stacked assemblies is of importance in biological systems and functional polymeric materials. To examine the requirements for exciton and hole stabilization, cofacial bifluorene ( F 2) torsionomers were designed, synthesized, and characterized: unhindered (model) ^Me F 2, sterically hindered ^tBu F 2, and cyclophane‐like ^C F 2, where fluorenes are locked in a perfect sandwich orientation via two methylene linkers. This set of bichromophores with varied torsional rigidity and orbital overlap shows that exciton stabilization requires a perfect sandwich‐like arrangement, as seen by strong excimeric‐like emission only in ^C F 2 and ^Me F 2. In contrast, hole delocalization is less geometrically restrictive and occurs even in sterically hindered ^tBu F 2, as judged by 160 mV hole stabilization and a near‐IR band in the spectrum of its cation radical. These findings underscore the diverse requirements for charge and energy delocalization across π‐stacked assemblies.     

A Rapidly Self‐Healing Host–Guest Supramolecular Hydrogel with High Mechanical Strength and Excellent Biocompatibility

It is still a challenge to achieve both excellent mechanical strength and biocompatibility in hydrogels. In this study, we exploited two interactions to form a novel biocompatible, slicing‐resistant, and self‐healing hydrogel. The first was molecular host–guest recognition between a host (isocyanatoethyl acrylate modified β‐cyclodextrin) and a guest (2‐(2‐(2‐(2‐(adamantyl‐1‐oxy)ethoxy)ethoxy)ethoxy)ethanol acrylate) to form “three‐arm” host–guest supramolecules (HGSMs), and the second was covalent bonding between HGSMs (achieved by UV‐initiated polymerization) to form strong cross‐links in the hydrogel. The host–guest interaction enabled the hydrogel to rapidly self‐heal. When it was cut, fresh surfaces were formed with dangling host and guest molecules (due to the breaking of host–guest recognition), which rapidly recognized each other again to heal the hydrogel by recombination of the cut surfaces. The smart hydrogels hold promise for use as biomaterials for soft‐tissue repair.     

BSA‐IrO2: Catalase‐like Nanoparticles with High Photothermal Conversion Efficiency and a High X‐ray Absorption Coefficient for Anti‐inflammation and Antitumor Theranostics

Intrinsically integrating precise diagnosis, effective therapy, and self‐anti‐inflammatory action into a single nanoparticle is attractive for tumor treatment and future clinical application, but still remains a great challenge. In this study, bovine serum albumin–iridium oxide nanoparticles (BSA‐IrO₂ NPs) with extraordinary photothermal conversion efficiency, good photocatalytic activity, and a high X‐ray absorption coefficient were prepared through one‐step biomineralization. The nanoparticles allow tumor phototherapy and simultaneous photoacoustic/thermal imaging and computed tomography. More importantly, BSA‐IrO₂ NPs can also act as a catalase to protect normal cells against H₂O₂‐induced reactive oxygen pressure and inflammation while significantly enhancing photoacoustic imaging through microbubble‐based inertial cavitation. These remarkable features may open up the exploration iridium‐based nanomaterials in theranostics.     

High‐Frequency Fe–H Vibrations in a Bridging Hydride Complex Characterized by NRVS and DFT

High‐spin iron species with bridging hydrides have been detected in species trapped during nitrogenase catalysis, but there are few general methods of evaluating Fe?H bonds in high‐spin multinuclear iron systems. An ⁵⁷Fe nuclear resonance vibrational spectroscopy (NRVS) study on an Fe(μ‐H)₂Fe model complex reveals Fe?H stretching vibrations for bridging hydrides at frequencies greater than 1200 cm^?1. These isotope‐sensitive vibrational bands are not evident in infrared (IR) spectra, showing the power of NRVS for identifying hydrides in this high‐spin iron system. Complementary density functional theory (DFT) calculations elucidate the normal modes of the rhomboidal iron hydride core.     

Photo‐Controlled Reversible Microtubule Assembly Mediated by Paclitaxel‐Modified Cyclodextrin

The design and construction of multi‐stimuli‐responsive supramolecular nanoassemblies that can mimic and regulate the fundamental biological processes have become a focus of interest in supramolecular chemistry. In this work, a perfect combination has been achieved between naturally occurring microtubules and artificially macrocyclic receptors. The self‐assembling morphology of microtubules can be photo‐tuned by the host–guest interaction of paclitaxel‐modified β‐cyclodextrin (PTX‐CD) and photochromic arylazopyrazole (PTX‐AAP). Moreover, the supramolecularly aggregated microtubules in a cellular environment can induce a pronounced cell morphological change and cell death. This supramolecular approach based on the secondary PTX‐AAP?PTX‐CD complexation provides us a facile method to reversibly control the intertubular aggregation behaviors of microtubules, which may bring new perspectives in the treatment of diseases related to improper protein aggregation.     

Cross‐Linked Aptamer–Lipid Micelles for Excellent Stability and Specificity in Target‐Cell Recognition

The specific binding ability of DNA–lipid micelles (DLMs) can be increased by the introduction of an aptamer. However, supramolecular micellar structures based on self‐assemblies of amphiphilic DLMs are expected to demonstrate low stability when interacting with cell membranes under certain conditions, which could lead to a reduction in selectivity for targeting cancer cells. We herein report a straightforward cross‐linking strategy that relies on a methacrylamide branch to link aptamer and lipid segments. By an efficient photoinduced polymerization process, covalently linked aptamer–lipid units help stabilize the micelle structure and enhance aptamer probe stability, further improving the targeting ability of the resulting nanoassembly. Besides the development of a facile cross‐linking method, this study clarifies the relationship between aptamer–lipid concentration and the corresponding binding ability.     

Structure and Dynamics in the Nucleosome Revealed by Solid‐State NMR

Eukaryotic chromatin structure and dynamics play key roles in genomic regulation. In the current study, the secondary structure and intramolecular dynamics of human histone H4 (hH4) in the nucleosome core particle (NCP) and in a nucleosome array are determined by solid‐state NMR (SSNMR). Secondary structure elements are successfully localized in the hH4 in the NCP precipitated with Mg²⁺. In particular, dynamics on nanosecond to microsecond and microsecond to millisecond timescales are elucidated, revealing diverse internal motions in the hH4 protein. Relatively higher flexibility is observed for residues participating in the regulation of chromatin mobility and DNA accessibility. Furthermore, our study reveals that hH4 in the nucleosome array adopts the same structure and show similar internal dynamics as that in the NCP assembly while exhibiting relatively restricted motions in several regions consisting of residues in the N‐terminus, Loop 1, and the α3 helix region.     

Formation of a Macrocycles‐in‐a‐Macrocycle Superstructure with All‐gauche Conformation by Reversible Radical Association

The formation of an unprecedented macrocycles‐in‐a‐macrocycle (MIM) superstructure by reversible radical–radical association of a triphenylamine based monomer terminated with three dicyanomethyl radicals is presented. The reaction yield is nearly quantitative and the obtained macrocycle contains three small dimeric macrocycles according to X‐ray crystallographic analysis. The six monomer molecules are linked by nine long dynamic covalent C(sp³)?C(sp³) bonds that all adopt a gauche conformation. Such a conformation favors the formation of a MIM structure rather than a 2D network with an all‐anti conformation. Two enantiomers with left‐/ right‐handed chirality exist in the single crystals of the superstructure.     

Introducing Fe2+ into Nickel–Iron Layered Double Hydroxide: Local Structure Modulated Water Oxidation Activity

Exploring materials with regulated local structures and understanding how the atomic motifs govern the reactivity and durability of catalysts are a critical challenge for designing advanced catalysts. Herein we report the tuning of the local atomic structure of nickel–iron layered double hydroxides (NiFe‐LDHs) by partially substituting Ni²⁺ with Fe²⁺ to introduce Fe‐O‐Fe moieties. These Fe²⁺‐containing NiFe‐LDHs exhibit enhanced oxygen evolution reaction (OER) activity with an ultralow overpotential of 195 mV at the current density of 10 mA cm^?2, which is among the best OER catalytic performance to date. In‐situ X‐ray absorption, Raman, and electrochemical analysis jointly reveal that the Fe‐O‐Fe motifs could stabilize high‐valent metal sites at low overpotentials, thereby enhancing the OER activity. These results reveal the importance of tuning the local atomic structure for designing high efficiency electrocatalysts.     

Bandgap‐Tunable Preparation of Smooth and Large Two‐Dimensional Antimonene

As a highly stable band gap semiconductor, antimonene is an intriguing two‐dimensional (2D) material in optoelectronics. However, its short layer distance and strong binding energy make it challenging to prepare high‐quality large 2D antimonene; therefore, its predicted tunable band gap has not been experimentally confirmed. Now, an approach to prepare smooth and large 2D antimonene with uniform layers that uses a pregrinding and subsequent sonication‐assisted liquid‐phase exfoliation process has been established. Mortar pregrinding provides a shear force along the layer surfaces, forming large, thin antimony plates, which can then easily be exfoliated into smooth, large antimonene, avoiding long sonication times and antimonene destruction. The resulting antimonene also enabled verification of the tunable band gap from 0.8 eV to 1.44 eV. Hole extraction and current enhancement by about 30 % occurred when the antimonene was used as a hole transport layer in perovskite solar cells.