Chemistry - A European Journal最新文献

A molecular-level understanding of supramolecular chirality amplification and attenuation is established through the coordination-driven self-assembly of a 'nano-size' achiral Zn(II)porphyrin trimer (host) and a series of chiral diamino esters (substrates). The processes occur through the stepwise formation of polymer and dimer via intermolecular assembling and disassembling processes, respectively. Crystallographic characterizations of both the polymer and dimer allow systematic scrutiny of their structural changes, elucidating their chiroptical properties. The electronic circular dichroism (CD) spectra display opposite signs for the R and S substrates in both the polymer and dimer, indicating that the chirality of the complexes are dictated solely by the absolute configuration of the substrate. In the dimer, both intra- and intermolecular couplings were identified while in the polymer, CD signals were significantly amplified, owing to cumulative intermolecular couplings. DFT and TDDFT studies corroborate these experimental findings and provide valuable insights into the origin of the chiroptical responses, amplification and reduction in these systems.

Reproducibility is the main weak point of most of the currently available synthetic strategies for metal nanostructures, and this issue is hampering both production and research on such materials. While several synthetic strategies can be found in literature, most of them are fundamentally based on strict protocols consisting of lists of subsequential predefined operations to be executed in a time-defined manner. Such protocols are designed and optimized on the basis of pilot runs and are intrinsically affected by noncontrollable fluctuations in the experimental conditions. In this work an innovative, intrinsically flexible, automatized, and self-correcting strategy is proposed, which, in combination with real-time monitoring of the optical properties of the reaction mixture, allows to synthesize precisely tuned gold nanorods. This strategy is based on the fast and precisely controlled oxidation of precursor AuNRs. The fast reaction allows the selective and predictable etching of the nanorods by online-controlled subsequential additions of small amounts of oxidants, which are also able to remove undesirably shaped byproducts possibly present in the sample. Due to these features, this process can be automated and allows starting from nonpurified nanorod dispersions with variable aspect-ratio. Furthermore, the reaction can be stopped by oxidizer quenching, providing stable dispersions.

The intricate structures of RNA molecules facilitate their diverse cellular functions. These structures are shaped by the cellular environment, a context that in silico and in vitro methods typically cannot reconstitute, making it more difficult to study the structure of RNA in cells. In response to these challenges, RNA structure probing using cell-permeable chemicals has emerged as an effective method to capture the RNA structural landscape in its native environment. The integration of these probes with advanced adduct detection techniques, particularly second- and third-generation sequencing, has propelled the field forward, facilitating a deeper understanding of the RNA structurome within its precise functional context, including the examination of RNA structure at the single-molecule and single-cell levels, within specific subcellular compartments, and across various stages of RNA biogenesis and regulation. This Review summarizes the significant advances in the field of RNA structure probing, focusing on the development of novel structural probes, strategies for RNA structure reconstruction, innovative methodologies that offer extended applicability to address unique biological questions, and concludes with an outlook on future directions in the field.

Electron donor-acceptor (EDA) complexes have emerged as powerful tools in radical chemistry, enabling diverse transformations under mild conditions. Among various EDA models, hydrogen‑bonding EDA (H-EDA) complexes, which utilize hydrogen‑bonding interactions to facilitate electron transfer between donors and acceptors, have attracted considerable attention in recent years. Owing to their unique advantages, broad substrate compatibility, tunable selectivity, and environmental friendliness, H‑EDA complexes represent promising candidates for advancing the fields of radical photochemistry and synthetic chemistry. This concept review delves into the foundational principles, mechanistic insights, and synthetic applications of H-EDA complexes in radical chemistry, and forward-looking perspectives on the future research trajectories of this field.

A mixed-linker synthetic strategy was employed to engineer the morphology of copper-triazolate metal-organic frameworks (Cu-Tz MOFs) through controlled crystal growth. By incorporating amino- and thioether-functionalized triazole alongside the parent triazole linkers, the framework's hydrophilicity, pore cavity, and surface chemistry were systematically modulated. Upon thermal activation, the resulting mixed-linker MOFs revealed accessible Cu(II) open metal sites, together with enhanced hydrophilicity and porosity within the framework. These features synergistically contribute to superior water removal performance from azeotropic water-ethanol mixtures, outperforming the parent CuTz in separation efficiency.

We explored aryl thianthrenation as a tool for directly incorporating multiple isotopes into molecular scaffolds starting from full isotopically labeled benzene. Stable isotope-labeled (SIL) molecules are indispensable tools for investigating chemical and biological mechanisms and quantifying metabolites. However, the late-stage incorporation of isotopically labeled benzene remains challenging and under-investigated. This challenge stems from the direct functionalization of non-substituted benzene, which remains a difficult task. The approach described in this work is based on sulfonium salts used as a source of [¹³C₆] and [²H₅]benzene under palladium catalysis conditions. This approach demonstrates its efficiency in C─C and C─S bond formation with different substrates. Additionally, this methodology was employed for the synthesis of poly-substituted [¹³C₆]benzene derivatives.

Nucleic acids exhibit diverse biological functions through hierarchical structural organization, and higher-order architectures enable recognition beyond Watson-Crick base pairing. Here, we describe the discovery and characterization of an unusual, extraordinarily stable motif-mini-hairpin DNA-a compact hairpin structure composed of GCGNNAGC or GCGNAGC sequences (N = A, G, C, or T). About 40 years ago, we serendipitously found this unique structure from unusual mobility in denaturing gel electrophoresis. The tertiary structure of GCGAAGC was determined by NMR and contains two G-C pairs and one sheared G-A pair. Despite only three base pairs, the mini-hairpin structure remains nondenatured even in 7 M urea. This thermal stability cannot be accounted for by conventional thermodynamic or structural models and remains unexplained by current molecular dynamics predictions. In addition to thermal stability, this motif resists nuclease digestion. The motif has been identified not only in certain genomic contexts but also as a stabilizing element in engineered nucleic acids, where it enhances the performance of functional nucleic acid molecules. We hope that this review will accelerate further research and applications of mini-hairpin DNA.

The physical and chemical behavior of CO₂ is key to understanding the ubiquity of inorganic carbon, which includes atmospheric CO₂, dissolved CO₂ in surface waters, and precipitated and mineralized carbonate in sediments and rock formations. These complex equilibria contribute to the global carbon cycle, inspiring novel CO₂ applications. Because water is crucial in these equilibria, a comprehensive overview of CO₂ reactivity in aqueous systems can help us to design and enhance the efficiencies of various artificial CO₂-mediated processes. Here, we discuss the role of CO₂ in responsive processes in, on, and with water, ranging from catalysis and organic synthesis to materials, surfactants, and carbon capture methods. These concepts are necessary for developing innovative smart materials, drug delivery systems, stimuli-controlled catalysis, novel environmental remediation processes, and new CO₂ capture materials. We rationalize these recent examples in terms of mod of action of CO₂ to recapitulate this rapidly developing field.

The precise engineering of surfaces decorated with polypeptides is critical for advanced diagnostics, biomedical coatings, and cellular interfaces. However, conventional methods are plagued by the need for solvents, multistep procedures, substrate limitations, and the abundance of side reactions. Here, we report that two-step chemical vapor polymerization can result in the fast, efficient, and substrate-independent synthesis of polypeptide films without the use of solvents or excipients. The first step involves deposition of an initiator layer, i.e., poly(4-amino-p-xylylene), via chemical vapor deposition (CVD) polymerization of 4,16-diamino[2.2]paracyclophane. The second step involves evaporation and ring-opening polymerization of N-carboxy anhydrides. This fully integrated CVD approach ensures substrate-independent, conformal growth of poly(propargyl-(S)-glycine) and poly(O-propargyl-(S)-tyrosine) films of up to 198 nm thickness. The use of CVD processes eliminates the concern of side reactions, such as transfer and termination reactions, and is a prerequisite for the successful peptide micropatterning, demonstrated in this study. Successful peptide growth and post-polymerization modifications via click chemistry were confirmed by time-of-flight secondary mass spectrometry, x-ray photoelectron spectroscopy, and infrared spectroscopy. The application of entirely solvent-free workflows to develop biomacromolecular coatings, such as the polypeptide films demonstrated in this study, addresses a critical gap in the pursuit of advanced and scalable biologization methods.

Air-stable nitrogen-centered radicals are of great interest as building blocks for functional molecular materials. In this study, we developed 2,2'-azobispyridine radical-boron complexes that exhibit near-infrared (NIR) absorption. The complexes were synthesized by introducing boron substituents into 2,2'-azobispyridine frameworks, followed by one-electron oxidation to generate the corresponding radical species. The B(C₆F₅)₂ derivatives were successfully isolated as air- and water-stable solids, whereas the BF₂ and B(n-Bu)₂ analogues could not be obtained. Electron spin resonance (ESR) spectroscopy revealed broad isotropic signals with g ≈ 2.00, indicating that the unpaired electron is delocalized over the 2,2'-azobispyridine core. Density functional theory (DFT) calculations supported this delocalization and reproduced the observed structural changes, including a N─N bond shortening upon oxidation. Single-crystal X-ray diffraction analysis of the methoxy-substituted complex confirmed these structural features. The radical complexes displayed NIR absorption with λ_max values of 800-1140 nm, depending on the substituents. These findings demonstrate that boron complexation effectively stabilizes 2,2'-azobispyridine radicals and enables precise tuning of their optical properties, providing a promising design principle for NIR functional dyes and radical-based materials.