Search Results (266)

A rational synthesis of the branched decaarabinofuranoside with 4-(2-azidoethoxy)phenyl aglycone (a Janus aglycone) related to the non-reducing terminal fragments of the arabinogalactan and lipoarabinomannan from Mycobacterium tuberculosis was proposed. Since the most challenging step is the formation of a 1,2-cis glycosidic linkage, we have significantly simplified access to a library of oligoarabinofuranosides derived from Mycobacterium tuberculosis polysaccharides using a silylated Ara-β-(1→2)-Ara disaccharide as the glycosyl donor. The application of a Janus aglycone also allowed us to reduce the number of reaction steps in glycoside synthesis. The obtained arabinans can be useful to further prepare conjugates as antigens for creating tuberculosis screening assays. Full article

The global market for flame-retardant materials is expected to grow steadily, from USD 7.0 billion in 2022 to USD 16.6 billion in 2030, driven by increasing demand for environment-friendly fire safety solutions in transportation, construction, and electronics. Polylactic acid (PLA), a biodegradable polymer which possesses excellent mechanical properties, is increasingly being considered for future mobility applications. However, it is characterized by high heat release and toxic smoke during combustion, which are significant drawbacks. In order to address this, the chemical modification of Kraft lignin was achieved through a phenolation and subsequent silylation with tetraethoxysilane, aiming to mitigate the degradation of PLA’s mechanical properties while utilizing its inherent char-forming ability. The modified lignins were combined with ammonium polyphosphate (APP) and melt-mixed with PLA using an injection-mixing molder to prepare test specimens. Analysis by FT-IR, NMR spectroscopy, and SEM-EDS confirmed successful grafting of phenolic and silane functionalities, and thermogravimetric analysis demonstrated enhanced thermal stability of the modified lignins compared to unmodified ones. Vertical burning tests and limiting oxygen index (LOI) measurements showed that the PLA/APP/SPKL composite material achieved a V-0 UL-94 rating and 31.95% LOI, demonstrating the highest level of flame retardancy. This compares to the LOI of neat PLA, 19 to 21%. Despite the enhancement in flame retardancy to the V-0 level, the decline in tensile strength was limited, and the composite retained comparable mechanical strength to PLA-APP composites with V-2 flame retardancy. The findings indicate that the combination of phenolation and silylation of lignin with APP, a flame-retardant material, offers a viable and sustainable methodology for the fabrication of PLA composites that exhibit both flame retardancy and mechanical strength. Full article

Silicon oxycarbide coatings are the subject of research due to their exceptional optical, electronic, anti-corrosion, etc., properties, which make them attractive for a number of applications. In this article, we present a study on the synthesis and characterization of thin SiOC:H silicon oxycarbide films with the given composition and properties from a new organosilicon precursor octamethyl-1,4-dioxatetrasilacyclohexane (²D₂) and its macromolecular equivalent—poly(oxybisdimethylsily1ene) (POBDMS). Layers from ²D₂ precursor with different SiOC:H structure, from polymeric to ceramic-like, were produced in the remote microwave hydrogen plasma by CVD method (RHP-CVD) on a heated substrate in the temperature range of 30–400 °C. SiOC:H polymer layers from POEDMS were deposited from solution by spin coating and then crosslinked in RHP via the breaking of the Si-Si silyl bonds initiated by hydrogen radicals. The properties of SiOC:H layers obtained by both methods were compared. The density of the cross-linked materials was determined by the gravimetric method, elemental composition by means of XPS, chemical structure by FTIR spectroscopy, and NMR spectroscopy (¹³C, ²⁹Si). Photoluminescence analyses and ellipsometric measurements were also performed. Surface morphology was characterized by AFM. Based on the obtained results, a mechanism of initiation, growth, and cross-linking of the CVD layers under the influence of hydrogen radicals was proposed. Full article

Silylation treatment improves the hydrophobicity of cellulose by reducing the number of hydroxyl groups in the cellulose chains that are available to react with moisture in the surrounding environment. Additionally, silylation increases stress transfer from cellulose to synthetic nanofillers by forming covalent bonds between the hydroxyl groups of cellulose and the oxidized surface of these nanofillers. This study investigates the impact of silane coupling agents on the tensile properties of cellulose nanocomposites. The cellulose nanocomposites are reinforced with four types of C/SiC-based nanofillers: carbon nanotubes, graphene nanoplatelets, silicon carbide nanotubes, and silicon carbide nanoplatelets. Subsequently, the nanofillers are subjected to surface treatment using the silane coupling agent KH550. The mechanical properties of the cellulose nanocomposites are evaluated by molecular dynamics simulations based on the polymer’s consistent forcefield. The results indicate that the reinforcements of silylated silicon carbide nanotubes and carbon nanotubes increase the tensile modulus of cellulose by 18.03% and 24.58%, respectively, compared to their untreated counterparts. Furthermore, the application of silylation treatment on the surface of C/SiC nanofillers increases the yield strength and ultimate tensile strength of cellulose nanocomposites due to enhanced load transfer between cellulose and these reinforcements. Full article

This study aims to develop a robust and reproducible method for fabricating efficient ultrathin antifouling coatings on gold surfaces by leveraging hydroxylation-based surface modifications. An ultrathin antifouling coating of a monoethylene glycol silane derivative, known to reduce fouling by at least 90% on flat hydroxylated surfaces, was successfully replicated on flat gold (reducing fouling by ~75%) by hydroxylating its surface with β-mercaptoethanol. This tandem coating contains the monoethylene glycol silane layer on top of the β-mercaptoethanol on the gold. Characterization was performed using contact angle goniometry, atomic force microscopy, x-ray photoelectron spectroscopy, and antifouling measurements. The results from these techniques, consistent with the literature, confirmed the successful and reproducible application of the tandem coating. Through heterogeneities, including defects and incomplete coverage, the AFM data revealed distinct visible layers of the tandem coating. The direct application of monoethylene glycol silane onto gold resulted in superior antifouling performance (88% reduction), demonstrating that direct silylation exploits pre-existing oxygen-containing species on the gold surface for a more effective antifouling layer. These findings offer a scalable approach for engineering antifouling coatings on gold substrates, with potential applications in biosensing and implantable device antifouling technologies. Full article

The quality of persimmon wine is closely related to various compounds, including polysaccharides. Polysaccharides are an essential class of macromolecules that modulate the wine’s chemical and physical characteristics by influencing the colloidal state or interacting with other compounds through non-covalent bonds. Polyphenols, on the other hand, exhibit antioxidant properties and effectively neutralize free radicals. This study employed Luotian sweet persimmons and Brassica napus (rapeseed) as core ingredients for producing functional fermented wine. Using GC-MS, rapeseed polysaccharides were subjected to trifluoroacetic acid hydrolysis and then derivatized via silylation for qualitative analysis of their monosaccharide composition. Molecular docking and molecular dynamics simulations were performed to provide molecular-level insights into the interactions between D-glucopyranose from rapeseed polysaccharides and quercetin, a polyphenol present in persimmon wine. The objective was to explore the binding mechanisms of these compounds during fermentation and to assess how these molecular interactions in-fluence the wine’s flavor and stability. In addition, volatile flavor compounds in two types of persimmon wine (pure persimmon wine and oleoresin-enriched persimmon wine) were qualitatively and quantitatively analyzed using headspace solid-phase microextraction (SPME) combined with gas chromatography–mass spectrometry (GC-MS). The results reveal that D-glucopyranose forms hydrogen bonds with quercetin, modulating its redox behavior and thereby enhancing the antioxidant capacity of persimmon wine. The results from four in vitro antioxidant assays, including DPPH, ABTS, FRAP, and vitamin C analysis, demonstrate that the addition of rapeseed flowers improved the antioxidant activity of persimmon wine. HS-SPME-GC-MS analysis revealed that esters, alcohols, and aldehydes were the primary components contributing to the aroma of persimmon wine. Persimmon wines with varying levels of oleoresin addition exhibited significant differences in the contents of key compounds, which subsequently influenced the aroma complexity and flavor balance. In conclusion, these findings provide reliable data and a theoretical foundation for understanding the role of rapeseed flower in regulating the aroma profile of persimmon wine. These findings also offer theoretical support for a deeper understanding of the fermentation mechanisms of persimmon wine while providing practical guidance to optimize production processes, ultimately improving both product flavor and stability. This study fills a critical academic gap in understanding microscopic molecular interactions during fermentation and offers a novel perspective for innovation in the fermented food industry. Full article

Background/Objectives: While various nucleoside and nucleotide analogs have been approved as anticancer and antiviral drugs, their limitations, including low bioavailability and chemotherapeutic resistance, encourage the development of novel structures. In this context, and motivated by our previous findings on bioactive 3′-O-substituted xylofuranosyl nucleosides and 5-guanidine xylofuranose derivatives, we present herein the synthesis and biological evaluation of 5′-guanidino furanosyl nucleosides comprising 6-chloropurine and uracil moieties and a 3-O-benzyl xylofuranosyl unit. Methods: The synthetic methodology was based on the N-glycosylation of a 5-azido 3-O-benzyl xylofuranosyl acetate donor with the silylated nucleobase and a subsequent one-pot sequential two-step protocol involving Staudinger reduction of the thus-obtained 5-azido uracil and N⁷/N⁹-linked purine nucleosides followed by guanidinylation with N,N′-bis(tert-butoxycarbonyl)-N′′-triflylguanidine. The molecules were evaluated for their anticancer and anti-neurodegenerative diseases potential. Results: 5′-Guanidino 6-chloropurine nucleosides revealed dual anticancer and butyrylcholinesterase (BChE)-inhibitory effects. Both N⁹/N⁷-linked nucleosides exhibited mixed-type and selective submicromolar/micromolar BChE inhibiton. The N⁹ regioisomer was the best inhibitor (K_i/K_i′ = 0.89 μM/2.96 μM), while showing low cytotoxicity to FL83B hepatocytes and no cytotoxicity to human neuroblastoma cells (SH-SY5Y). Moreover, the N⁹-linked nucleoside exhibited selective cytotoxicity to prostate cancer cells (DU-145; IC₅₀ = 27.63 μM), while its N⁷ regioisomer was active against all cancer cells tested [DU-145, IC₅₀ = 24.48 μM; colorectal adenocarcinoma (HCT-15, IC₅₀ = 64.07 μM); and breast adenocarcinoma (MCF-7, IC₅₀ = 43.67 μM)]. In turn, the 5′-guanidino uracil nucleoside displayed selective cytotoxicity to HCT-15 cells (IC₅₀ = 76.02 μM) and also showed neuroprotective potential in a Parkinson’s disease SH-SY5Y cells’ damage model. The active molecules exhibited IC₅₀ values close to or lower than those of standard drugs, and comparable, or not significant, neuro- and hepatotoxicity. Conclusions: These findings demonstrate the interest of combining guanidine moieties with nucleoside frameworks towards the search for new therapeutic agents. Full article

Chelation-assisted olefinic C–H functionalization has been demonstrated to be a powerful method of constructing multi-substituted alkenes from simpler ones. This strategy produces complex alkenes in a regio- and stereoselective manner, followed by C–H endo- and exo-cyclometallation. Among the various directing groups developed, N,N- and N,O-bidentate directing groups are the most widely used to selectively promote C–H functionalization due to their fine, tunable, and reversible coordination with the metal center. In this review, we discuss various N,N- and N,O-bidentate directing group-assisted olefinic C–H bond functionalization reactions, including alkenylation, alkylation, arylation, thiolation, silylation, halogenation, and cyclization. Full article

A disila[2]ferrocenophane bearing a 9,9′-bi-9H-9-silafluorene (9-silafluorene dimer) moiety as a bridging unit was synthesized and isolated as a stable crystalline compound. Disila[2]ferrocenophane 1, newly obtained in this study, has been characterized by spectroscopic analyses, single crystal X-ray diffraction (SC-XRD) analysis, and electrochemical measurements. It was found that the obtained disila[2]ferrocenophane was reduced by a reducing agent to generate the corresponding 1,1′-ferrocenediyl-bis(silylanion) via the reductive Si–Si σ-bond cleavage. The trapping reactions of the 1,1′-ferrocenediyl-bis(silylanion) thus generated with electrophiles have also been attempted. Full article

The incorporation of transition metal atoms into [Ge₉] clusters is a widely studied area of Zintl-cluster chemistry. Recently, it was shown that clusters comprising single transition metal atoms in the cluster surface show catalytic properties. Here, we present a synthetic approach to four new compounds comprising silylated Ge₉ clusters with organometallic ruthenium complexes. [η⁵-Ge₉Hyp₃]RuCp* (1), [η¹-Ge₉(Si^tBu₂H)₃]RuCp(PPh₃)₂ (2), and [Hyp₃Ge₉][RuCp(PPh₃)₂(MeCN)] (3b) (Cp = cyclopentadienyl, Cp* = pentamethylcyclopentadienyl, Hyp = Si(SiMe₃)₃, Ph = C₆H₅, ^tBu = tert-butyl) were characterized by means of NMR spectroscopy and single-crystal structure determination. In the case of 2, a new isomer with an approximated C_4v symmetric monocapped square antiprism of nine Ge atoms with an unexpected ligand arrangement comprising three ditertbutylsilane ligands attached to the open square was obtained. [Hyp₃Ge₉][RuCp(PPh₃)₂] (3a) was characterized via NMR spectroscopy and LIFDI mass spectrometry. Overall, we were able to show that the steric demand of the ligands Cp vs. Cp* and hypersilylchloride vs. ditertbutylsilane strongly influence the arrangement of the atoms and ligands on the cluster. In addition, the solvent also affects the cluster, as it appears that the ruthenium atom in 3a dissociates from the cluster surface upon acetonitrile coordination to form 3b. These results show that choosing the right synthetic tools and ligands makes a big difference in the outcome of the metalation reaction. Full article

Modern organic synthesis continues to benefit from the flexibility of α-diazo carbonyl intermediates. In the context of homologation processes, the Roskamp reaction—first introduced in 1989—has become a valuable tool due to its selectivity and mild condition reactions for accessing important synthons amenable to further functionalization as β-keto esters. The fine-tuning of reaction parameters—including the nature of Lewis acids, solvents, and temperature—has enabled the development of catalyzed continuous-flow methodologies, as well as a series of asymmetric variants characterized by high transformation rates, excellent stereocontrol, and formidable chemoselectivity. This review aims to emphasize the attractive features of the Roskamp reaction and its applicability for addressing challenging homologation processes. Full article

Increasing the number of SiMe₃ substituents on a cyclopentadienyl ring has, in addition to a stabilizing effect of unusual coordination geometries and oxidation states, the effect of increasing the solubility in unpolar solvents and increasing the volatility. Starting from pentabromoferrocene and pentabromo(pentamethyl)ruthenocene, we could achieve the introduction of up to five silyl (SiMe₂H or SiMe₃) groups to give [Fe(C₅H₅){C₅(SiMe₂R)₅}], R = H, Me, and [Ru(C₅Me₅){C₅(SiMe₂H)₅}]. However, yields were very low, and nearly all intermediate steps afforded mixtures of similar silyl-substituted compounds, which were difficult to separate. The crystal structures of [Fe(C₅H₅){C₅(SiMe₂H)₅}] (13a), [Fe(C₅H₅){C₅Br₃(SiMe₃)₂}] (4b), and [Fe(C₅H₅){C₅Br₂(SiMe₃)₃}] (8b) were determined. Full article

When fabricating Si-based devices, many process steps require the use of expensive, high-power consumption, environmentally unfriendly, operator-unsafe machines, and processes. Among the many involved process steps, the ones needed to fabricate the metallurgical junction make use of conventional doping methods, which do not always represent optimal solutions. The high costs of the processing equipment and the use of hazardous materials, not to count the structural damage produced, intrinsically limit future developments towards nm-scaled and low cost approaches. Recently a chemistry-based method has been proposed to form the junction on Si, the so-called molecular doping. In this approach, the samples to be doped are subjected to a silylation process, during which a layer of dopant-containing molecules is deposited in a liquid bath kept at boiling temperature. After the coating, the samples are annealed to decompose the molecule and release the dopants inside the target. The peculiarity of using a liquid source allows for avoiding the structural damage. The entire doping procedure is simple and cost-effective, and it is based on the use of ester molecules, which are less harmful than the standard materials. In this work, we present experimental results on this chemistry-based technique, demonstrating its efficiency in creating the junction and demonstrate its feasibility in the fabrication of solar cells prototypes. Moreover, with respect to the literature, we show for the first time the effects of the protective layer presence over the dopant source molecules in the final solar cells electrical properties. As a proof of concept, we have numerically investigated the Si-based solar cell using the SCPAS-1D simulator. The finding claims that, the proposed samples have a good match in terms of the performance of the devices compared to the conventional Si-solar cells. Henceforth, the proposed work can provide a guideline to achieve less expensive, more environmentally friendly techniques for molecular doping in Si without affecting its performance in the metallurgical junction. Full article

In the field of medicinal chemistry, the introduction of silylated groups is an important strategy to alter the activity, selectivity, and pharmacokinetics of compounds based on the diverse traits of silicon, including atomic size, electronegativity, and hydrophobicity. The hydroxy group on C-9 or C-9 and C-10 of hydroxystearic acids have been functionalized as t-butyl dimethyl silyl ether. The target compounds have been fully characterized and tested for in vitro cytotoxicity in tumor cells HT29, HCT116, CaCo2, HeLa, MCF7, U2OS, and Jurkat J6 and normal I407 cells. In particular, the silyl derivative of (R)-9-hydroxystearic acid was more active in colon cancer cells. Analyses of cell proliferation, oxidative cell status, histones post-translational modifications, protein phosphorylation, gene expression, and DNA damage were performed to obtain information on the antitumor properties of the new molecules in comparison with the unmodified (R)-9-hydroxystearic acid’s previously studied effects. Our results suggest that the incorporation of a silyl functionality may be a useful tool for the structural development of new pharmaceutically active compounds against colon cancer. Full article

This study evaluated the stability and reusability of amino-functionalized nanocellulose aerogels as CO₂-adsorbent materials. The modified aerogels, synthesized via a controlled silylation using N-[3-(trimethoxysilyl) propyl] ethylenediamine (DAMO), demonstrated excellent thermal stability up to 250 °C (TGA) and efficient CO₂ adsorption through chemisorption, which was the main adsorption mechanism. The performance of the aerogels was assessed using both adsorption isotherms and the decay pressure technique, revealing that CO₂ adsorption capacity increased with higher amino group loading (4.62, 9.24, and 13.87 mmol of DAMO). At 298 K and 4 bar, CO₂ adsorption capacity increased proportionally with the amino group concentration, reaching values of 3.17, 5.98, and 7.86 mmol of CO₂ g⁻¹ polymer, respectively. Furthermore, over 20 adsorption/desorption cycles, the aerogels maintained 95% CO₂ desorption at ambient temperature, indicating their potential for industrial use. These findings highlight the aerogels suitability as stable, reusable materials for large scale CO₂ capture and storage technologies. Full article