Cover Picture: Engineered SAM Synthetases for Enzymatic Generation of AdoMet Analogs with Photocaging Groups and Reversible DNA Modification in Cascade Reactions (Angew. Chem. Int. Ed. 1/2021)

A New Nonlinear Optical Material with N(CN)2 - Anion

Discovering new functional genes and developing high-performance materials are the goals being pursued by scientists. In this work, we successfully obtained a second-order nonlinear optical (NLO) material via the aqueous solution method, Y[N(CN)₂ ]₄ [NH(C₂ H₅ )₃ ] ⋅ 3H₂ O, which is the first NLO material with the anionic group N(CN)₂ ^- . Remarkably, this material is not only strongly NLO-active at 1064 nm with a response of about 2.8 × KH₂ PO₄ , but also possesses a short UV absorption edge of 250 nm. In-depth first-principles calculations illustrate well that the optical properties are mainly from the strong interaction of N, C and Y atoms. This result indicates that the N(CN)₂ ^- anion may be a new NLO functional gene. This work enriches the diversity of NLO functional genes and materials.

An aqueous polyethylene oxide-based solid-state electrolyte with high voltage stability for dendrite-free lithium deposition via a self-healing electrostatic shield

Lithium metal batteries (LMBs) have attracted extensive attention for their ultrahigh energy density. However, the uncontrollable growth of Li-dendrites results in poor cyclability and potential safety risks, thus preventing their practical application. Herein, a flexible and cost-effective aqueous polyethylene oxide (PEO)-based solid-state electrolyte is prepared, which enables uniform and dendrite-free Li deposition by introducing Cs⁺ with an electrostatic shielding mechanism at high current densities. The self-assembly of PEO and bacterial cellulose by hydrogen bonding reduces the crystallinity of PEO and increases uniformly the distribution of lithium ions. With excellent flexibility and thermal stability, such a 3D polymer solid-state electrolyte exhibits an enhanced electrochemical stability window of 5.8 V versus Li/Li⁺ potential and a high ionic conductivity of 1.28 × 10^-4 S cm^-1 at 60 °C. The Li|BC-PEO-Cs⁺|Li symmetric cells operate stably for more than 1000 h. Furthermore, Li|BC-PEO-Cs⁺|LiFePO₄ (LFP) cells show remarkable enhancement in capacity (163.4 mA h g^-1 at 0.1 C), cycling stability (with a capacity retention of 96% after 500 cycles at 1 C) and high functionality and safety (withstanding folding and cutting) in practical applications.

Visualizing designer quantum states in stable macrocycle quantum corrals

Creating atomically precise quantum architectures with high digital fidelity and desired quantum states is an important goal in a new era of quantum technology. The strategy of creating these quantum nanostructures mainly relies on atom-by-atom, molecule-by-molecule manipulation or molecular assembly through non-covalent interactions, which thus lack sufficient chemical robustness required for on-chip quantum device operation at elevated temperature. Here, we report a bottom-up synthesis of covalently linked organic quantum corrals (OQCs) with atomic precision to induce the formation of topology-controlled quantum resonance states, arising from a collective interference of scattered electron waves inside the quantum nanocavities. Individual OQCs host a series of atomic orbital-like resonance states whose orbital hybridization into artificial homo-diatomic and hetero-diatomic molecular-like resonance states can be constructed in Cassini oval-shaped OQCs with desired topologies corroborated by joint ab initio and analytic calculations. Our studies open up a new avenue to fabricate covalently linked large-sized OQCs with atomic precision to engineer desired quantum states with high chemical robustness and digital fidelity for future practical applications.

Surface chiroselective assembly of enantiopure crystalline porous films containing bichiral building blocks

The development of chiral crystalline porous materials (CPMs) containing multiple chiral building blocks plays an important role in chiral chemistry and applications but is a challenging task. Herein, we report the first example of bichiral building block based enantiopure CPM films containing metal-organic cages (MOCs) and metal complexes. The functionalized substrate was immersed subsequently into homochiral metal complex (R)- or (S)-Mn(DCH)3 (DCH = 1,2-diaminocyclohexane) and racemic Ti4L6 cage (L = embonate) solutions by a layer-by-layer growth method. During the assembly process, the substrate surface coordinated with (R)- or (S)-Mn(DCH)3 can, respectively, layer-by-layer chiroselectively connect Δ- or Λ-Ti4L6 cages to form homochiral (R, Δ)- or (S, Λ)-CPM films with a preferred [111] growth orientation, tunable thickness and homogeneous surface. The resulting enantiopure CPM films show strong chirality, photoluminescence, and circularly polarized luminescence (CPL) properties as well as good enantioselective adsorption toward enantiomers of 2-butanol and methyl-lactate. The present in situ surface chiroselective strategy opens a new route to assemble homochiral CPM films containing multiple chiral building blocks for chiral applications.

Titanium content influence on the optical response characteristics of TiO2/ormosils composite films doped with azobenzene

TiO₂-based organic-inorganic composite films doped with azobenzene and photosensitive groups were prepared by combining a low-temperature solgel technique and a spin-coating method. The influence of TiO₂ content on the optical and structural properties of the composite films including the film thickness, the refractive index, the transmission loss, the thermal gravity analysis, and Fourier transform infrared spectroscopy spectra was studied. Photoisomerization and optical switching characteristics of the composite film were investigated under the irradiation of 365 nm ultraviolet light and 450 nm visible light. Results indicate that several micrometer thick films can be easily obtained at room temperature and there is a proportional relationship between the refractive index value and the TiO₂ content. In addition, the composite films have a low optical propagation loss of about 0.1 dB/cm. The composite films with 0.2 M TiO₂ content have an obvious photoisomerization and good optical switching properties. Finally, the hexagonal microlens array was fabricated in the composite films by using an ultraviolet nanoimprint technology. All these results above indicate that the as-prepared TiO₂-based organic-inorganic composite film has potential applications in optical switching devices and photonic elements.

Pd(ii)-Catalyzed regioselective functionalization of antipyrines: synthesis of pyrazolono-maleimides and pyrazolono-quinones

A Pd(ii)-catalyzed direct functionalization reaction of the 4Csp²-H bond of antipyrine derivatives is reported. This metal-catalyzed reaction of antipyrines with maleimides provided an easy and efficient access to biologically important pyrazolonomaleimides. This catalytic system is also applicable for C-4 functionalization of the antipyrine ring with quinone derivatives.

Intertwined Analytical, Experimental and Theoretical Studies on the Formation and Structure of a Copper Dienolate

The reaction of a silyl dienolate, a Cu(II) salt and TBAT yielding the corresponding copper dienolate is addressed. A combined NMR and cyclic voltammetry analysis first highlight the role of TBAT in the Cu(II) to Cu(I) reduction and the structure of the precatalytic species. From these first results a second set of NMR and theoretical studies enable the determination of the structure and the mechanism of formation of the copper dienolate catalytic species. Finally, we showed that that the copper catalyst promote the E/Z s-cis/s-trans equilibration of the silyl dienolate precursor through a copper dienolate intermediate. All of these results unveil some peculiarities of the catalytic and asymmetric vinylogous Mukaiyama reaction.

Single microbead-based fluorescent aptasensor (SMFA) for direct isolation and in situ quantification of exosomes from plasma

Exosomes are cell-derived membrane-enclosed biological nanoparticles that carry lots of parental molecular information, and are recognized as an ideal biomarker for non-invasive diagnosis. However, due to the low abundance of exosomes in plasma samples and the interferences from complex biological matrices, the sensitive and direct detection of exosomes still remains a challenge. Here, by combining the direct magnetic isolation with in situ fluorescence imaging, we developed a Single Microbead-based Fluorescent Aptasensor (SMFA) for specific enrichment and sensitive quantification of exosomes from plasma. In the SMFA, a single aptamer-modified microbead (MB) served as the reaction carrier so that the specific exosomes inserted with a fluorescent anchor will be highly enriched on the single MB. By in situ fluorescence imaging to monitor the fluorescence signals on the single MB, sensitive detection of exosomes can be realized without the requirement of any signal amplification routes, and as low as 4.9 × 10⁴ particles per μL of exosomes could be simply detected. More importantly, the SMFA could be applied for direct detection of the exosomes from small amounts of clinical plasma samples without prior purification procedures, indicating its great potential applications in clinical diagnostics.

Photothermal treatment of oropharyngeal cancer with carbon-defective silicon carbide

Oral squamous carcinoma (OSCC) is a clinical common tumor with high recurrence rate and low 5 year survival rate. In this work, photothermal antitumor treatment has been performed to treat OSCC by taking anti-wound infection into consideration. By introducing C defects, we have successfully converted the semi-conductive SiC into metallic carbon-defective silicon carbide (SiC1-x), and endowed it with the near infrared absorption property for photothermal therapy (PTT). The results revealed that SiC1-x mediated PTT treatment could remove solid OSCC tumor in a biosafe way, showing low hematotoxicity, cytotoxicity and tissue toxicity. Moreover, the low invasion of PTT treatment could not only prevent the invasion of bacteria, but also realize an antibacterial effect on the wound, both of which are important for oral surgery. SiC1-x could be excreted from the body post treatment, which thus reduces the long-term potential toxicity. On the whole, this study provided a promising way to treat OSCC in an effective and safe way.