Chemistry - A European Journal最新文献

The properties of high-pressure liquid water were investigated along the isobar of 25 MPa and in the temperature range 298.15-623.15 K using classical molecular dynamics simulations. Particular attention has been given to the changes in the local structural and related dynamic properties of liquid water. The results obtained have revealed noticeable changes in the shape of the calculated radial distribution functions, as well as the existence of local extrema or crossovers in several structural descriptors and entropic quantities at temperatures around 423.15 K and 498.15 K, where also significant changes in the hydrogen bond network of liquid water have also been observed. The temperature dependence of translational, reorientational and hydrogen bond dynamics of liquid water has also been investigated by calculating the translational self-diffusion and the corresponding O-H vector Legendre reorientational correlation times and hydrogen bond lifetimes. The corresponding activation energies for each investigated relaxation process have also been presented and discussed.

The first examples of air and water stable bis(germylenes) 5-9 and bis(germacarbonyl) compounds 10-12 are reported. Bis(germylene monochloride) 5 is isolated by starting from bis(dipyrromethene) 4, which in turn has been synthesized by oxidizing bis(dipyrromethane) 3 using DDQ. Terephthaldehyde 1 and mesityl pyrrole 2 were the precursors for compound 3. Bis(germylene monochloride) 5 reacts with alcohols and phenol in the presence of a mild base (Cs₂CO₃) to afford bis(germylene alkoxides) 6-7 and bis(germylene phenoxide) 8, respectively. Compound 5's reaction with sodium pyrrolide has resulted in bis(germylene pyrrolide) 9. Further, compounds 7 and 9 react with elemental sulfur and selenium under ambient conditions, resulting in bis(germacarbonyl) compounds 10-12. The UV-Vis spectroscopic investigations on compounds 4-12 are done experimentally and computationally.

Using GPU-accelerated molecular dynamics, V. Maréchal, J.-P. Piquemal and co-workers have modeled the structural dynamics of the PKM2 and PKM1 enzymes. Performing over 6 μs of simulation with the AMOEBA polarizable force field, they identified key structural properties of the proteins binding sites and determined new cryptic pockets for potential antiviral/antitumoral further designs. More information can be found in their Research Article (DOI: 10.1002/chem.202402534).

Nitrocyclopropanes, a special class of donor–acceptor cyclopropanes, are considered to be stepping stones in organic synthesis. Due to the versatile nature of the nitro group, they can be converted into other functional heterocyclic or scaffolds of higher structural complexity to provide access to biologically active molecules. In their Review (DOI: 10.1002/chem.202404791), A. G. Chaidali, M. A. Terzidis and I. N. Lykakis have gathered and categorised the various synthetic methodologies based on the origin of the nitro group. The results of an application-focused analysis highlight the importance of nitrocyclopropanes as key intermediates.

Difunctionalization of olefins serves as the workhorse for rapid creation of molecular complexity from simple feedstocks. However, these reactions are mostly restricted to the 1,2-variant, with higher homologations being attempted to a much lesser extent. Radical translocation strategies serve as an escape from the traditional 1,2-strategies, providing a means for achieving distant functionalizations that are otherwise difficult to access. Herein, we disclose visible light-mediated strategies for the accessing of 1,3-, 1,4-, 1,5-, and 1,6-aminophosphonates via combination of various radical shifting methods. In addition, the aminophosphorylation of σ-bonds was also achieved, leading to 1,3-aminophosphorylated cyclobutanes.

The azido modified RNA cleaving catalyst 2 has been attached to oligonucleotides containing alkyne linkers in a central position. The resulting conjugates hybridize specifically with complementary RNA strands and cleave them with multiple substrate turnover. RNA half-lives are in the range of 6-7 h (pH 8, 37 °C). Some well placed LNA nucleotides can further increase substrate affinities and reaction rates significantly (t½ of 3.5 h, kobs = 0.20 h-1). RNA cleavage does not require metal ions and runs equally well in the presence of EDTA. Fragments of precisely defined lengths are formed, well suited for subsequent analysis by mass spectrometry and related bioanalytical techniques.

The colors of substances and emission are determined by the width of the energy gap between frontier molecular orbitals. In general, significant structural transformation or chemical modification is essential to tune the energy gap. Herein, we reveal a hypervalent silicon compound can form both square pyramidal (SP) and trigonal bipyramidal (TBP) geometries and demonstrate a novel technique to modulate the energy gap of the π-conjugated system. The energy gap in the TBP geometry is narrower than that in the SP geometry owing to stronger contribution of a polarized three-center four-electron (3c-4e) bond and a nitrogen-silicon (N-Si) coordination, and the geometries are changeable by external stimuli such as photoirradiation and temperature variations. Correspondingly, the emission bands in the orange (λPL = 640 nm) and yellow (λPL = 579 nm) regions were observed from the TBP geometry at room temperature and the SP geometry at -196 °C, respectively. Furthermore, the geometry can be fixed to the TBP geometry by introducing bulky substituents at silicon. These mechanisms are experimentally and theoretically clarified in detail. Our findings described here are expected to be a novel molecular design for creating stimuli-responsive materials.

The search for safer and more effective vaccine adjuvants has intensified in recent years, with triterpenoid saponins like QS-21 and its analogues emerging as promising candidates. We report the synthesis of a novel QS-21 analogue featuring betulinic acid as aglycone, a lupane-type triterpenoid with low toxicity derived from white birch bark. Two convergent synthetic routes, involving different protecting groups and glycosyl donors (bromide and trichloroacetimidate), were optimized to construct the QS-21-based linear trisaccharide motif critical for adjuvant activity. This strategy also enabled efficient preparation of the structurally similar echinocystic acid analogue reported by Gin. The immunological and toxicological profiles of these chimeric saponins, along with Lewis-X-containing and rhamnose-modified derivatives, were evaluated in C57BL/6 wild-type and hDC-SIGN transgenic mice. While the synthetic saponins exhibited low toxicity in vitro and in vivo, replacing echinocystic acid with betulinic acid reduced immunogenicity when tested with ovalbumin as a model antigen compared to alhydrogel and QS-21. These findings provide a foundation for developing saponin-based adjuvants and demonstrate the utility of advanced glycosylation strategies for synthesizing complex unnatural triterpenoid saponins.

Naphthalimide-based self-assembled materials have gained significant attention in recent years because of their exceptional versatility and wide range of applications, from sensors and electronics to biomedical. Naphthalimides derivatives, with ease of functionalization and robust photophysical properties, became an ideal platform for creating highly ordered self-assembled architectures with tailored functionalities. This review provides an overall understanding of the recent developments in the synthesis and self-assembly of naphthalimide-based materials, focusing on how self-assembly enhances their performance in various applications. The review examines the role of self-assembly in improving these materials' optical, mechanical, and electronic properties, highlighting their use in sensors for detecting gases, volatile organic compounds (VOCs), and amines. Furthermore, the integration of self-assembled naphthalimides in light-emitting devices, energy harvesting systems, and fluorescence-based imaging demonstrates their potential in both electronic and biological applications. By analysing recent developments in molecular design, self-assembly strategies, and applications, this review aims to offer insights into how these materials can be optimized for future technological advancements.

Efforts to enhance photocatalysts prioritize improving their accessibility and practicality in photocatalytic applications. Supramolecular (auto)photocatalysis, which exploits transient self-assembled complexes, facilitates visible light-driven reactions, with autocatalytic systems promoting sustainable and atom-economical processes. In this study, the photocatalyst Mes-Acr-MeClO4, typically active under blue light, formed a dark red charge-transfer (CT) complex with N-bromoacetamide (NBA) in the presence of K2CO3 in DCE, enabling green-light photocatalysis. This self-assembled CT complex initiated an auto-photocatalytic process via two-photon absorption, generating an N-centered radical that drove anti-Markovnikov, syn-periplanar addition to phenylacetylene, achieving exclusive Z-selective formation of (Z)-N-(2-bromo-2-phenylvinyl)acetamide. Interestingly, the product itself functioned as a potent green-LED photocatalyst (λem ~518 nm, τ ~10 ns), driving its own synthesis with added terminal alkynes. With 100% atom economy, this work highlights a system chemistry approach, showcasing a highly efficient, self-sustaining catalytic process that advances green and sustainable synthetic strategies. This protocol emphasizes sustainability with an outstanding E-factor of 11.15, reflecting minimal waste production (11.15 kg per 1 kg of product) and demonstrating a strong commitment to green chemistry principles.