ACS Organic & Inorganic Au最新文献

Phthalocyanine-gold nanoparticle (Pc-AuNP) conjugates combine the unique properties of gold with the therapeutic potential of phthalocyanines, offering a promising strategy for cancer therapy. Here, two novel carbazole-containing Pcs, axially disubstituted Si-(IV) and peripherally tetra-substituted Zn-(II) derivatives, were synthesized and conjugated to gold nanoparticles of two core sizes (20 and 40 nm). Characterization was performed using TEM and SEM techniques. Stability assays in complete medium showed a stronger aggregation tendency for SiPc-AuNPs than for ZnPc-AuNPs. Bright-field microscopy revealed that Pc-AuNPs induced detachment of A549 lung adenocarcinoma cells but not HUVEC endothelial cells, highlighting a cell type-dependent effect. Despite this detachment, no significant loss of viability occurred at 72 h, underscoring the resilience of A549 cells to membrane and cytoskeletal stress. Once internalized, both SiPc- and ZnPc-based nanoconjugates displayed similar cytoplasmic and perinuclear localization, suggesting uptake was dominated by the AuNP carrier. Preliminary MTT assays showed dye-particle interference, leading to use of the PrestoBlue assay, which avoids insoluble formazan artifacts. Viability analysis indicated that only Au40/SiPc transiently increased A549 reducing capacity at 24 h, likely due to short-term ROS scavenging, which normalized by 72 h. Overall, these findings demonstrate how metal center, substitution geometry, and particle size collectively affect aggregation, cellular interactions, and cytotoxic profiles, providing insights for optimizing Pc-AuNPs as nanophototherapeutic agents.

Late-stage catalytic oxidations of complex natural products have been shown to exhibit dramatically improved chemoselectivity through the crucial use of 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP), even in the presence of oxidatively sensitive groups, such as hydroxyls and diols. This strategy reduced the need for protecting groups, effectively mimicking enzymatic pathways, and substantially enhancing synthetic ideality in the preparation of ent-beyerane and ent-kaurane metabolites.

For the first time, we present fluorinated analogs of Streptococcus pneumoniae serotype 14 (SPn14)-specific tetrasaccharide antigens originating from the repeating unit {6)-[β-d-Galp-(1→4)-]-β-d-GlcpNAc-(1→3)-β-d-Galp-(1→4)-β-d-Glcp-(1→} _n of the capsule's outer cell surface, featuring different strategic fluorination sites. These modified pneumococcal tetrasaccharides are also equipped with allyl groups at the reducing end to enable further functionalization. Key transformation steps during the synthesis of these target molecules included (1 + 1)-glycosylations of fluorinated galactosyl donors as well as late fluorination steps, which were selectively performed on lactosyl building blocks. The subsequent central (2 + 2) couplings of the lactosyl donors with the respective lactosaminyl building blocks proceeded with good yields, enabling the synthesis of the desired target tetrasaccharide antigen analogs in amounts sufficient for future biological investigations following a global deprotection protocol. A total of six novel F-analogs of the SPn14 glycotope were produced using the methods described herein.

A practical and scalable protocol for the deoxyfluorination of hydroxyalkyl-substituted aryl- and alkenylboronates was developed. The optimized conditions (combining Deoxo-Fluor with TEA·3HF as the reagents and substrate preconversion to trifluoroborate salts) enabled efficient transformation across a wide range of (homo)-benzylic and allylic alcohols while tolerating protected carboxyl and amino groups. The resulting fluorinated boronates performed well as versatile building blocks in oxidation and Suzuki cross-coupling reactions. Furthermore, a telescoped one-pot strategy allowed direct utilization of crude fluorinated intermediates, enabling access to complex molecular frameworks containing alcohol, carbonyl, and ester functionalities, typically intolerant to late-stage fluorination conditions. This methodology offers a general and efficient route for the incorporation of monofluorinated aliphatic fragments into structures that are relevant for medicinal chemistry and materials science.

In solid-state compounds, the valence of europium can sometimes be mixed, which is especially favored in structures with several positions for the europium atoms. In this work, we study the Eu-based intermetallic noncentrosymmetric system Eu_11-x Hg_54+x , which has 65 atoms per unit cell and 4 distinct crystallographic positions for europium and 14 positions for mercury. Our detailed analysis of the magnetism of large single crystals suggests that europium in Eu_11-x Hg_54+x might be present in two valence states, resulting in a fragile magnetic ground state. Due to the cage-like structure with a large distance between the Eu atoms, those atoms are weakly ferromagnetically coupled and Eu_11-x Hg_54+x orders at low temperatures, below T ₁ = 5.5 K, with a subsequent spin reorientation at T ₂ = 4.3 K. There is no sign of magnetic frustration. Interestingly, the magnetic ordering of the europium substructure results in a magnetization pole reversal with a delicate ferrimagnetic ground state. Additional magnetic phases can be induced by the application of a modest external magnetic field.

The heterogenization of homogeneous photocatalysts on inert supports such as silica and alumina offers more than improved recyclability. Unlike semiconducting supports such as titanium dioxide, which can alter the photocatalyst behavior through electron injection, insulating oxides preserve the intrinsic photophysical and redox properties of the molecular species. However, such heterogenization is an opportunity to completely modify the physicochemical properties of the surrounding environment, thereby influencing excited-state properties and enhancing reactivity and stability as well as compatibility with green solvents and flow systems. In addition, advanced support design introduces further potential for selectivity or reactivity with gas, although these remain largely underexplored. While silica is widely used due to its tunability and surface area, alumina offers complementary properties but remains less developed. This review highlights the early stage, yet rapidly evolving landscape of heterogenized photocatalysts on silica and alumina, emphasizing the emerging functionalities that extend well beyond catalyst recovery.

We have developed a synthesis of 29 novel 1,2,4-triazolidines using tertiary amine N-oxides and a wide range of substituted azoarenes. Our method utilizes a base-mediated [3 + 2] cycloaddition, starting from either commercially available or easily accessible precursors to generate triazolidines in yields up to 99%. Density functional theory calculations were performed in parallel to the experimental work to provide insights into the reactivity patterns and the overall mechanism. Finally, preliminary biological data are included on the antibacterial properties of these compounds.

Hydrazones are a versatile class of molecular switches with dual responsiveness to both light and pH. To investigate their switching properties, we incorporated a nitroxide moiety, enabling analysis by not only conventional techniques such as ¹H NMR and UV-vis spectroscopy but also EPR spectroscopy, which provides valuable insights into structure and dynamics. A novel nitroxide-substituted hydrazone switch (2) was synthesized and fully characterized. However, initial experiments using ¹H NMR and UV-vis revealed restricted photoisomerization of 2. Theoretical studies employing DFT and TD-DFT methods revealed the presence of the D₁ excited state related to π → π* electron transfer of the nitroxide moiety, and D₂ excited state related to π → π* electron transfer within the hydrazone moiety. The latter excitation results in weakening of the CN bond and enables the rotation around the hydrazone bond; however, the internal conversion D₂ → D₁ process is most likely responsible for the quenching of photoisomerization in 2. Additionally, pH-induced switching was monitored using UV-vis and EPR spectroscopy, revealing that strong acids such as trifluoroacetic acid had no significant effect on the paramagnetic center.

The photoisomerization of isoxazoles is an atom-economical route to carbonyl-2H-azirines, which are valuable in both synthetic and biological applications. However, isolation of the carbonyl-2H-azirine is challenged by reverse photoisomerization back to the isoxazole and irreversible rearrangement to an oxazole. In this work, we demonstrate that substituent selection on 3,5-disubstituted isoxazoles plays a critical role in driving the photochemical isoxazole-azirine equilibrium toward the carbonyl-2H-azirine while avoiding oxazole formation. We find that substituents affect the degree of overlap in the absorption spectra of isoxazole-azirine pairs, where reducing overlap increases the efficiency of photoisomerization. We use time-dependent density functional theory to predict absorption spectra for isomer pairs with varied 3,5-disubstituents, identifying tert-butyl- and trifluoromethyl-substituted 5-aminoisoxazoles as promising structures. We then tested these predictions experimentally, revealing efficient formation of carbonyl-2H-azirines in high yields with minimal oxazole formation. This is in contrast to a phenyl-substituted 5-aminoisoxazole, which was found to readily form oxazoles, precluding isolation of the carbonyl-2H-azirine. These results demonstrate the utility of substituent-driven design for tuning photoisomerization equilibria and provide an atom-economical option for generating carbonyl-2H-azirines on synthetically useful scales.