Journal of the American Chemical Society最新文献

Spherical supramolecular dendrimers including helical, self-organize soft Frank-Kasper, other cubic such as body-centered cubic, and quasicrystal periodic and quasiperiodic arrays. When any of these periodic or quasiperiodic arrays forms immediately above a columnar phase, a supramolecular orientational memory effect was found to discriminate between mechanisms of self-organization of supramolecular spheres and generate unprecedented periodic arrays of helical columns which cannot be constructed by any other methodology. Here, we demonstrate that unwinding spherical helices, via their precursor nonhelical columns, increases the entropy and stability of their periodic and quasiperiodic spherical arrays and places the Frank-Kasper and other cubic phases immediately above the columnar phase. This process is not available in biology where spherical viruses self-organize body-centered cubic lattices. However, this concept reengineers, on increasing temperature, the originally expected position of the periodic and quasiperiodic array versus that of the columnar lattice. This process facilitates discrimination between different self-organization mechanisms of supramolecular spheres and also mediates the emergence of unprecedentedly complex and technologically important periodic arrays of nonhelical columns.

Polymer-in-salt electrolytes were introduced three decades ago as an innovative solution to the challenge of low Li-ion conductivity in solvent-free solid polymer electrolytes. Despite significant progress, the approach still faces considerable challenges, ranging from a fundamental understanding to the development of suitable polymers and salts. A critical issue is maintaining both the stability and high conductivity of molten salts within a polymer matrix, which has constrained their further exploration. This research offers a promising solution by integrating cationic poly(ionic liquids) (polyIL) with a crystallization-resistive salt consisting of asymmetric anions. A stable polymer-in-salt electrolyte with an exceptionally high Li-salt content of up to 90 mol % was achieved, providing a valuable opportunity for the in-depth understanding of these electrolytes at an extremely high salt concentration. This work explicates how increased salt concentration affects coordination structures, glass transitions, ionic conductivity, and the decoupling and coupling of ion transport from structural dynamics in a polymer electrolyte, ultimately enhancing electrolyte performance. These findings provide significant knowledge advancement in the field, guiding the future design of polymer-in-salt electrolytes.

A family of Pd₂L₄ cages prepared from ligands based on an axially chiral diamino-[1,1'-biazulene] motif (serving as a unique azulene-based surrogate of the ubiquitous BINOL moiety) is reported. We show that preparing a cage starting from the racemate of a shorter bis-monodentate ligand derivative, equipped with pyridine donor groups, leads to integrative ("social") chiral self-sorting, exclusively yielding the meso-trans product, but only in a selection of solvents. This phenomenon is driven by individual solvent molecules acting as hydrogen bonding tethers between the amino groups of neighboring ligands, thereby locking the final coordination cage in a single isomeric form. The experimental (solvent-dependent NMR, single-crystal X-ray diffraction) observations of this cooperative interaction could be explained by computational analyses only when explicit solvation was considered. Furthermore, we prepared a larger chiral ligand with isoquinoline donors, which, unlike the first one, does not undergo social self-sorting from its racemic mixture, further highlighting the importance of solvents bridging short distances between the amino groups. Homochiral cages formed from this larger ligand, however, furnish a cavity that can bind anionic and neutral metal complexes such as [Pt(CN)₆]^2- and Cr(CO)₆ and discriminate between the two enantiomers of chiral guest camphor sulfonate.

Messenger RNA (mRNA) vaccines have exhibited enormous potential in the treatment of human diseases; however, their widespread applications are curtailed by the induction of reactive oxygen species during mRNA translation, which greatly compromises the translation efficiency. Herein, we present a robust strategy with the capability to substantially enhance the efficacy of the mRNA vaccine through promoting mRNA translation and stimulator of interferon genes (STING) activation. The strategy entails the coassembly of small-sized manganese oxide nanoparticles (Mn₃O₄ NPs) with lipid nanoparticles (LNPs) as the hybrid delivery vehicle (MnLNPs) for the fabrication of mRNA vaccine. The acquired MnLNPs proficiently scavenge reactive oxygen species (ROS) produced during mRNA translation and facilitate oxygen production, thereby boosting adenosine triphosphate (ATP) synthesis and augmenting mRNA translation. Furthermore, MnLNPs effectively bolster the antigen presentation and maturation of dendritic cells by activating the cGAS-STING pathway. In vivo studies demonstrate that mRNA vaccine prepared from MnLNPs markedly enhances the translation of antigen-encoding mRNA compared to LNPs, leading to superior antitumor efficacy. The tumor-suppressive capabilities of MnLNPs@mRNA are further promoted by synergizing with immune checkpoint blockade, underscoring MnLNPs-based mRNA vaccine as an exceptionally promising avenue in cancer immunotherapy.

Organic molecules with an aggregation-induced emission (AIE) property have been attracting much attention from the viewpoint of application to solid state emissive materials. For the AIE mechanism, quantum mechanical studies proposed the restriction of the intramolecular motion (RIM) model with the contribution of the conical intersection (CI) and deduced the importance of the restricted access to a conical intersection (RACI) in the potential energy surface (PES). Although these theoretical studies have contributed to the elucidation of AIE phenomena, direct detection of the reaction dynamics is indispensable to clarify the actual PES and the deactivation mechanism. Along this line, we investigated excited state dynamics of the AIE molecule with dibenzoylmethanatoboron difluoride complexes using time-resolved absorption spectroscopies in both visible and infrared (IR) regions. While the reference system of 1,3-bis(4-methoxyphenyl)methanatoboron difluoride (2aBF₂) showed strong emission in solution, the methyl-substituted derivative at the α-position of the dioxaborine ring (2amBF₂) led to the very weak fluorescence in solution but strong emission in the solid state. Time-resolved visible absorption measurements revealed a peak shift and broadening of the stimulated emission in the solution of 2amBF₂, owing to the rapid change of the molecular geometry. With the temporal evolution of time-resolved IR absorption signals and density functional theory (DFT) calculation of these systems, it was deduced that 2amBF₂ has two stable geometries, namely, planar and bending, in the S₁ state and the bending geometry in the S₁ state led to rapid conversion to the S₀ state. These results support the RACI model in the aggregated states, leading to the AIE properties.

Light-assisted synthesis of ammonia from nitrate and nitrite sources is a sustainable approach to reduce the burden of the energy-intensive Haber-Bosch process. However, poor selectivity and the need for UV-active photocatalysts are the current bottlenecks in the synthesis of ammonia from nitrate and nitrite sources. Herein, we introduce selective visible-light-driven ammonia production from nitrate and nitrite ions with indium phosphide quantum dots (InP QDs) as the photocatalyst. The presence of catalytic indium sites and microenvironment modulation through an interplay of catalyst-reactant interactions resulted in efficient and selective ammonia formation under visible light. Ammonia was produced in an attractive yield of ∼94% in both aqueous and gaseous phases within 2 h of visible-light irradiation at room temperature. A decent formation of ammonia was observed under sunlight as well, strengthening the translational prospects of InP QD photocatalysts. Mechanistic investigations ascertained a negligible role of competing hydrogen evolution in direct nitrate reduction, confirming the active participation of photoexcited charge carriers from InP QDs in the ammonia synthesis. Kinetic studies revealed the energetically challenging nitrate-to-nitrite conversion as the rate-determining step, with subsequent reactions proceeding with ∼100% conversion to yield ammonia. A series of experiments concluded that water is the proton source in the InP QD-photocatalyzed synthesis of ammonia. Our study shows the impact of the rationally designed core and surface of InP QD-based photocatalysts in developing sustainable routes to produce ammonia beyond the Haber-Bosch process.