Journal of the American Chemical Society最新文献

Phosphine oxides and arsine oxides are common laboratory reagents with diverse applications that stem from the chemistry exhibited by these monomeric species. Stibine oxides are, in contrast, generally dimeric or oligomeric species because of the reactivity-quenching self-association of the highly polarized stiboryl (Sb=O/Sb⁺-O^-) group. We recently isolated Dipp₃SbO (Dipp = 2,6-diisopropylphenyl), the first example of a kinetically stabilized monomeric stibine oxide, which exists as a bench-stable solid and bears an unperturbed stiboryl group. Herein, we report the isolation of Mes₃SbO (Mes = mesityl), in which the less bulky substituents maintain the monomeric nature of the compound but unlock access to a wider range of reactivity at the unperturbed stiboryl group relative to Dipp₃SbO. Mes₃SbO was found to be a potent Lewis base in the formation of adducts with the main-group Lewis acids PbMe₃Cl and SnMe₃Cl. The accessible Lewis acidity at the Sb atom results in a change in the reactivity with GeMe₃Cl, SiMe₃Cl, and CPh₃Cl. With these species, Mes₃SbO formally adds the E-Cl (E = Ge, Si, C) bond across the unsaturated stiboryl group to form a 5-coordinate stiborane. The biphilicity of Mes₃SbO is sufficiently potent to activate even the C-F and Si-F bonds of C(p-MeOPh)₃F and SiEt₃F, respectively. These results mark a significant contribution to an increasingly rich literature on the reactivity of polar, unsaturated main-group motifs. Furthermore, these results highlight the utility of a kinetic stabilization approach to access unusual bonding motifs with unquenched reactivity that can be leveraged for small-molecule activation.

We report an electrochemical method for doping two-dimensional (2D) superatomic semiconductor Re₆Se₈Cl₂ that significantly improves the material's electrical transport while retaining the in-plane and stacking structures. The electrochemical reduction induces the complete dissociation of chloride anions from the surface of each superatomic nanosheet. After the material is dehalogenated, we observe the electrical conductivity (σ) increases by two orders of magnitude while the 3D electron carrier density (n_3D) increases by three orders of magnitude. In addition, the thermal activation energy (E_a) and electron mobility (μ_e) decrease. We conclude that we have achieved effective electron-doping in 2D superatomic Re₆Se₈Cl₂, which significantly improves the electrical transport properties. Our work sets the foundation for electrochemically doping and tuning the transport properties of other 2D superatomic materials.

We report the first total synthesis of hypersampsone M, an archetypal member of the homoadamantane polycyclic polyprenylated acylphloroglucinols (PPAPs). Commencing from cyclohexenone, a key cyclopentene annulation followed by ring-expansion results in an elusive hydrazulene that undergoes a series of unexpected late-stage transformations, ultimately enabling completion of the synthesis. The route detailed herein represents a potentially general strategy for the synthesis of related homoadamantane PPAPs.

The magnetoelectric material has attracted multidisciplinary interest in the past decade for its potential to accommodate various functions. Especially, the external electric field can drive the quantum behaviors of such materials via the spin-electric coupling effect, with the advantages of high spatial resolution and low energy cost. In this work, the spin-electric coupling effect of Mn²⁺-doped ferroelectric organic-inorganic hybrid perovskite [(CH₃)₃NCH₂Cl]CdCl₃ with a large piezoelectric effect was investigated. The electric field manipulation efficiency for the allowed transitions was determined by the pulsed electron paramagnetic resonance. The orientation-included Hamiltonian of the spin-electric coupling effect was obtained via simulating the angle-dependent electric field modulated continuous-wave electron paramagnetic resonance. The results demonstrate that the applied electric field affects not only the principal values of the zero-field splitting tensor but also its principal axis directions. This work proposes and exemplifies a route to understand the spin-electric coupling effect originating from the crystal field imposed on a spin ion being modified by the applied electric field, which may guide the rational screening and designing of hybrid perovskite ferroelectrics that satisfy the efficiency requirement of electric field manipulation of spins in quantum information applications.

The catalytic kinetic resolution of racemic β-branched aldehydes offers a straightforward stereoselective entry to aldehydes and addition products. Yet, control over stereoselectivity is difficult due to the conformational flexibility of β-branched aldehydes. Here, we show that the peptide catalyst H-dPro-αMePro-Glu-NH₂ resolves β-branched aldehydes through reaction with nitroolefins and provides γ-nitroaldehydes with three consecutive stereogenic centers in high yields and stereoselectivities. Kinetic, NMR spectroscopic, and computational studies provided insights into the selectivity-determining step and origins of the kinetic resolution.

Anthracenylidene is an intriguing structural unit with potential in various fields. The study presents a novel approach to introducing axial chirality into this all-carbon core skeleton through a remotely controlled desymmetrization strategy. A palladium-catalyzed enantioselective Heck arylation of exocyclic double bond of anthracene with two distinct substituents at the C10 position is harnessed to realize such a transformation. The judicious identification of the P-centrally chiral ligand is pivotal to ensure the competitive competence in reactivity and stereocontrol when the heteroatom handle is absent from the anthracenylidene skeleton. Both C10 mono- and disubstituted substrates were compatible for the established catalytic system, and structurally diverse anthracenylidene-based frameworks were forged with good-to-high enantiocontrol. The subsequent derivatization of the obtained products yielded a valuable array of centrally and axially chiral molecules, thus emphasizing the practicality of this chemistry. DFT calculations shed light on the catalytic mechanism and provided insights into the origin of the experimentally observed enantioselectivity for this reaction.

Mechanical recycling is one of the simplest and most economical strategies to address ever-increasing plastic pollution, but it cannot be applied to immiscible mixed plastics and suffers from property deterioration after each cycle. By combining the amphiphilic block copolymer strategy and reactive compatibilization strategy, we designed a series of stapler strategies for compatibilizing/upcycling mixed plastics. First, various functionalized graft copolymers were accessed via different synthetic routes. Subsequently, the addition of a very small amount of stapler molecules induced a synergistic effect with the graft copolymers that improved the compatibility and mechanical properties of mixed plastics. These strategies were highly effective for various binary/ternary plastic systems and can be directly applied to postconsumer waste plastics, which can increase the toughness of mixed postconsumer waste plastics by 162 times. Most importantly, it also effectively improved the impact resistance, adhesion performance, and three-dimensional (3D) printing performance of mixed plastics, and permitted the recycling of plastic blends 20 times with minimal degradation in their mechanical properties.

The development of intrinsically recyclable cross-linked materials remains challenged by the inherently unfavorable chemical equilibrium that dictates the efficiency of the reversible covalent bonding/debonding chemistry. Rather than having to (externally) manipulate the bonding equilibrium, we here introduce a new reversible chemistry platform based on monosubstituted thiomaleimides that can undergo complete and independent light-activated covalent bonding and on-demand thermal debonding above 120 °C. Specifically, repeated bonding/debonding of a small-molecule thiomaleimide [2 + 2] photodimer is demonstrated over five heat/light cycles with full conversion in both directions, thereby regenerating its initial monothiomaleimide constituents. This motivated the synthesis of multifunctional thiomaleimide reagents as precursors for the design of covalently cross-linked networks that display intrinsic switching between a monomeric and polymeric state. The resulting materials are shown to covalently dissociate and depolymerize upon heating both in solution and in bulk, thus transforming the densely photo-cross-linked material back into a viscous liquid. Temperature-regulated photorheology evidenced the intrinsic recyclability of the thiomaleimide-based thermosets during multiple cycles of UV cross-linking and thermal de-cross-linking. The thermally reversible photodimerization of thiomaleimides presents a new addition to the designer playground of dynamic polymer networks, providing interesting opportunities for the reprocessing and closed-loop recycling of covalently cross-linked materials.

The messenger RNA (mRNA) vaccines hold great significance in contagion prevention and cancer immunotherapy. However, safely and effectively harnessing innate immunity to stimulate robust and durable adaptive immune protection is crucial, yet challenging. In this study, we synthesized a library of stimuli-responsive bivalent ionizable lipids (srBiv iLPs) with smart molecular blocks responsive to esterase, H₂O₂, cytochrome P450, alkaline phosphatase, nitroreductase, or glutathione (GSH), aiming to leverage physiological cues to trigger fast lipid degradation, promote mRNA translation, and induce robust antitumor immunity via reactive oxygen species (ROS)-mediated boosting. After subcutaneous immunization, esterase-responsive vaccine (eBiv-mVac) was rapidly internalized and transported into the draining lymph nodes. It then underwent fast decaging and self-immolative degradation in esterase-rich antigen-presenting cells, releasing sufficient mRNA for antigen translation and massive reactive quinone methides to elevate ROS levels. This resulted in broad activation of innate immunity to boost T cell response, prompting a large number of primed antigen-specific CD8⁺ T cells to circulate and infiltrate into tumors (>1000-fold versus unvaccinated control), thereby orchestrating innate and adaptive immunity to control tumor growth. Moreover, by further combining our vaccination strategy with immune checkpoint blockade, we demonstrated a synergism that significantly amplified the magnitude and function of antigen-specific CD8⁺ T cells. This, in turn, caused potent systemic antitumor efficacy and prolonged survival with high complete response rate in xenograft and metastasis models. Overall, our generalized stimuli-responsive mRNA delivery platform promises a paradigm shift in the design of potent vaccines for cancer immunotherapy, as well as effective and precise carriers for gene editing, protein replacement, and cell engineering.

There has been much effort to improve excited-state lifetimes in photosensitizers based on earth-abundant first-row transition metals. Copper(I) complexes have gained significant attention in this field, and in most cases, sterically driven approaches are used to optimize their lifetimes. This study presents a series of three-coordinate copper(I) complexes (Cu1-Cu3) where the excited-state lifetime is extended by triplet-triplet energy transfer. The heteroleptic compounds feature a cyclohexyl-substituted β-diketiminate (CyNacNac^Me) paired with aryl isocyanide ligands, giving the general formula Cu(CyNacNac^Me)(CN-Ar) (CN-dmp = 2,6-dimethylphenyl isocyanide for Cu1; CN-pyr = 1-pyrenyl isocyanide for Cu2; CN-dmp-pyr = 2,6-dimethyl-4-(1-pyrenyl)phenyl isocyanide for Cu3). The nature, energies, and dynamics of the low-energy triplet excited states are assessed with a combination of photoluminescence measurements at room temperature and 77 K, ultrafast transient absorption (UFTA) spectroscopy, and DFT calculations. The complexes with the pyrene-decorated isocyanides (Cu2 and Cu3) exhibit extended excited-state lifetimes resulting from triplet-triplet energy transfer (TTET) between the short-lived charge-transfer excited state (³CT) and the long-lived pyrene-centered triplet state (³pyr). This TTET process is irreversible in Cu3, producing exclusively the ³pyr state, and in Cu2, the ³CT and ³pyr states are nearly isoenergetic, enabling reversible TTET and long-lived ³CT luminescence. The improved photophysical properties in Cu2 and Cu3 result in improvements in activity for both photocatalytic stilbene E/Z isomerization via triplet energy transfer and photoredox transformations involving hydrodebromination and C-O bond activation. These results illustrate that the extended excited-state lifetimes achieved through TTET result in newly conceived photosynthetically relevant earth-abundant transition metal complexes.