Photocatalyzed Aminomethylation of Alkyl Halides Enabled by Sterically Hindered N-Substituents

The catalytic C(sp³)−C(sp³) coupling of alkyl halides and tertiary amines offers a promising tool for the rapid decoration of amine skeletons. However, this approach has not been well established, partially due to the challenges in precisely distinguishing and controlling the reactivity of amine-coupling partners and their product homologues. Herein, we developed a metal-free photocatalytic system for the aminomethylation of alkyl halides through radical-involved C(sp³)−C(sp³) bond formation, allowing for the synthesis of sterically congested tertiary amines that are of interest in organic synthesis but not easily prepared by other methods. Mechanistic studies disclosed that sterically hindered N-substituents are key to activate the amine coupling partners by tuning their redox potentials to drive the reaction forward.     

Anomalous Charge Transfer from Organic Ligands to Metal Halides in Zero-Dimensional [(C6H5)4P]2SbCl5 Enabled by Pressure-Induced Lone Pair-π Interaction

Low-dimensional (low-D) organic metal halide hybrids (OMHHs) have emerged as fascinating candidates for optoelectronics due to their integrated properties from both organic and inorganic components. However, for most of low-D OMHHs, especially the zero-D (0D) compounds, the inferior electronic coupling between organic ligands and inorganic metal halides prevents efficient charge transfer at the hybrid interfaces and thus limits their further tunability of optical and electronic properties. Here, using pressure to regulate the interfacial interactions, efficient charge transfer from organic ligands to metal halides is achieved, which leads to a near-unity photoluminescence quantum yield (PLQY) at around 6.0 GPa in a 0D OMHH, [(C₆H₅)₄P]₂SbCl₅. In situ experimental characterizations and theoretical simulations reveal that the pressure-induced electronic coupling between the lone-pair electrons of Sb³⁺ and the π electrons of benzene ring (lp-π interaction) serves as an unexpected “bridge” for the charge transfer. Our work opens a versatile strategy for the new materials design by manipulating the lp-π interactions in organic–inorganic hybrid systems.     

Diastereoselective Biomimetic Synthesis of Dimeric Tetrahydrocarbazoles via a Copper(II)-Catalyzed Cycloisomerization-[3+2] Cyclodimerization Cascade

The cyclodimerization (homochiral- and heterochiral−) of monomeric units for the construction of stereodefined polycyclic systems is a powerful strategy in both biosynthesis and biomimetic synthesis. Herein we have discovered and developed a Cu^II- catalyzed, biomimetic, diastereoselective tandem cycloisomerization-[3+2] cyclodimerization of 1-(indol-2-yl)pent-4-yn-3-ol. This novel strategy operates under very mild conditions, providing access to structurally unprecedented dimeric tetrahydrocarbazoles fused to a tetrahydrofuran unit in excellent yields of the products. Several fruitful control experiments, isolation of the monomeric-cycloisomerized products and their subsequent conversion into the corresponding cyclodimeric products supported their intermediacy and the possible mechanism as a cycloisomerization-diastereoselective [3+2] cyclodimerization cascade. The cyclodimerization involves a substituent controlled, highly diastereoselective homochiral [3+2] annulation or heterochiral [3+2] annulation of in situ generated 3-hydroxytetrahydrocarbazoles. The key and important features of this strategy are: a) construction of three new C−C bonds & one new C−O bond; b) creation of two new stereocenters, and c) construction of three new rings, in a single operation; d) low catalyst loading (1–5 mol %); e) 100 % atom economy; and f) rapid construction of structurally unprecedented natural product like polycyclic frameworks. A chiral pool version using an enantio- and diastereopure substrate was also demonstrated.     

[2+2+1+1] Cycloaddition for de novo Synthesis of Densely Functionalized Phenols

A unique benzannulation strategy for regioselective de novo synthesis of densely functionalized phenols is described. Through metal-mediated formal [2+2+1+1] cycloaddition of two different alkynes and two molecules of CO, a series of densely functionalized phenols were obtained. The benzannulation strategy allows efficient regioselective installation up to five different substituents on a phenol ring. The resulting phenols have a substitution pattern different from those obtained from Dötz and Danheiser benzannulations.     

Cluster Light-Emitting Diodes Containing Copper Iodine Cube with 100 % Exciton Utilization Using Host-Cluster Synergy

Clusters combine the advantages of organic molecules and inorganic nanomaterials, which are promising alternatives for optoelectronic applications. Nonetheless, recently emerged cluster light-emitting diodes require further excited state optimization of cluster emitters, especially to reduce population of the cluster-centered triplet quenching state (³CC). Here we report that redox-active ligands enhance reverse intersystem crossing (RISC) of Cu₄I₄ cluster for triplet-to-singlet conversion, and thermally activated delayed fluorescence (TADF) host can provide an external RISC channel. It indicates that the complementarity between TADF host and cluster in RISC transitions gives rise to 100 % triplet conversion efficiency and complete singlet exciton convergence, rendering 100-fold increased singlet radiation rate constant and tenfold decreased triplet non-radiation rate constant. We achieve a photoluminescence quantum yield of 99 % and a record external quantum efficiency of 29.4 %.     

Steering the Selectivity of Electrocatalytic Glucose Oxidation by the Pt Oxidation State

Electrocatalytic glucose oxidation can produce high value chemicals, but selectivity needs to be improved. Here we elucidate the role of the Pt oxidation state on the activity and selectivity of electrocatalytic oxidation of glucose with a new analytical approach, using high-pressure liquid chromatography and high-pressure anion exchange chromatography. It was found that the type of oxidation, i.e. dehydrogenation of primary and secondary alcohol groups or oxygen transfer to aldehyde groups, strongly depends on the Pt oxidation state. Pt⁰ has a 7-fold higher activity for dehydrogenation reactions than for oxidation reactions, while PtO_x is equally active for both reactions. Thus, Pt⁰ promotes glucose dialdehyde formation, while PtO_x favors gluconate formation. The successive dehydrogenation of gluconate is achieved selectively at the primary alcohol group by Pt⁰, while PtO_x also promotes the dehydrogenation of secondary alcohol groups, resulting in more complex reaction mixtures.     

Insights into Anion-Solvent Interactions to Boost Stable Operation of Ether-Based Electrolytes in Pure-SiOx||LiNi0.8Mn0.1Co0.1O2 Full Cells

Ether solvents with superior reductive stability promise excellent interphasial stability with high-capacity anodes while the limited oxidative resistance hinders their high-voltage operation. Extending the intrinsic electrochemical stability of ether-based electrolytes to construct stable-cycling high-energy-density lithium-ion batteries is challenging but rewarding. Herein, the anion-solvent interactions were concerned as the key point to optimize the anodic stability of the ether-based electrolytes and an optimized interphase was realized on both pure-SiO_x anodes and LiNi_0.8Mn_0.1Co_0.1O₂ cathodes. Specifically, the small-anion-size LiNO₃ and tetrahydrofuran with high dipole moment to dielectric constant ratio realized strengthened anion-solvent interactions, which enhance the oxidative stability of the electrolyte. The designed ether-based electrolyte enabled a stable cycling performance over 500 cycles in pure-SiO_x||LiNi_0.8Mn_0.1Co_0.1O₂ full cell, demonstrating its superior practical prospects. This work provides new insight into the design of new electrolytes for emerging high-energy density lithium-ion batteries through the regulation of interactions between species in electrolytes.     

Mechanism of Cations Suppressing Proton Diffusion Kinetics for Electrocatalysis

Proton transfer is crucial for electrocatalysis. Accumulating cations at electrochemical interfaces can alter the proton transfer rate and then tune electrocatalytic performance. However, the mechanism for regulating proton transfer remains ambiguous. Here, we quantify the cation effect on proton diffusion in solution by hydrogen evolution on microelectrodes, revealing the rate can be suppressed by more than 10 times. Different from the prevalent opinions that proton transport is slowed down by modified electric field, we found water structure imposes a more evident effect on kinetics. FTIR test and path integral molecular dynamics simulation indicate that proton prefers to wander within the hydration shell of cations rather than to hop rapidly along water wires. Low connectivity of water networks disrupted by cations corrupts the fast-moving path in bulk water. This study highlights the promising way for regulating proton kinetics via a modified water structure.     

The Self-Association of the KRAS4b Protein is Altered by Lipid-Bilayer Composition and Electrostatics

KRAS is a peripheral membrane protein that regulates multiple signaling pathways, and is mutated in ≈30 % of cancers. Transient self-association of KRAS is essential for activation of the downstream effector RAF and oncogenicity. The presence of anionic phosphatidylserine (PS) lipids in the membrane was shown to promote KRAS self-assembly, however, the structural mechanisms remain elusive. Here, we employed nanodisc bilayers of defined lipid compositions, and probed the impact of PS concentration on KRAS self-association. Paramagnetic NMR experiments demonstrated the existence of two transient dimer conformations involving alternate electrostatic contacts between R135 and either D153 or E168 on the “α4/5-α4/5” interface, and revealed that lipid composition and salt modulate their dynamic equilibrium. These dimer interfaces were validated by charge-reversal mutants. This plasticity demonstrates how the dynamic KRAS dimerization interface responds to the environment, and likely extends to the assembly of other signaling complexes on the membrane.     

Carboxysome-Inspired Electrocatalysis using Enzymes for the Reduction of CO2 at Low Concentrations**

The electrolysis of dilute CO₂ streams suffers from low concentrations of dissolved substrate and its rapid depletion at the electrolyte-electrocatalyst interface. These limitations require first energy-intensive CO₂ capture and concentration, before electrolyzers can achieve acceptable performances. For direct electrocatalytic CO₂ reduction from low-concentration sources, we introduce a strategy that mimics the carboxysome in cyanobacteria by utilizing microcompartments with nanoconfined enzymes in a porous electrode. A carbonic anhydrase accelerates CO₂ hydration kinetics and minimizes substrate depletion by making all dissolved carbon available for utilization, while a highly efficient formate dehydrogenase reduces CO₂ cleanly to formate; down to even atmospheric concentrations of CO₂. This bio-inspired concept demonstrates that the carboxysome provides a viable blueprint for the reduction of low-concentration CO₂ streams to chemicals by using all forms of dissolved carbon.