Synthesis and characterization of a novel organic–inorganic hybrid salt and its application as a highly effectual Brønsted–Lewis acidic catalyst for the production of N,N′‐alkylidene bisamides

In this research, a novel organic–inorganic hybrid salt, namely, N¹,N¹,N²,N²‐tetramethyl‐N¹,N²‐bis(sulfo)ethane‐1,2‐diaminium tetrachloroferrate ([TMBSED][FeCl₄]₂) was prepared and characterized by Fourier‐transform infrared spectroscopy (FT‐IR), energy‐dispersive X‐ray spectroscopy (EDX), elemental mapping, field emission scanning electron microscopy (FE‐SEM), X‐ray diffraction (XRD), thermal gravimetric (TG), differential thermal gravimetric (DTG), and vibrating‐sample magnetometry (VSM) analyses. Catalytic activity of the hybrid salt was tested for the synthesis of N,N′‐alkylidene bisamides through the reaction of benzamide (2 eq.) and aromatic aldehydes (1 eq.) under solvent‐free conditions in which the products were obtained in high yields and short reaction times. The catalyst was superior to many of the reported catalysts in terms of two or more of these factors: the reaction medium and temperature, yield, time, and turnover frequency (TOF). [TMBSED][FeCl₄]₂ is a Brønsted–Lewis acidic catalyst; there are two SO₃H groups (as Brønsted acidic sites) and two tetrachloroferrate anions (as Lewis acidic sites) in its structure. Highly effectiveness of the catalyst for the synthesis of N,N′‐alkylidene bisamides can be attributed to synergy of the Brønsted and Lewis acids and also possessing two sites of each acid.     

Sensitive Voltammetric Method for Rapid Determination of Sarcosine as a New Biomarker for Prostate Cancer Using a TiO2 Nanoparticle/Ionic Liquid Modified Carbon Paste Electrode

Russian Journal of Electrochemistry - Sarcosine has been identified as a key metabolite marker for monitoring and early diagnosis of metastatic prostate cancer (PCa), and it is detectable in the...     

NiFe2O4@SiO2@Cu3(BTC)2 nanocomposite as a magnetic metal–organic framework

A new magnetic metal–organic framework (MOF), namely, NiFe₂O₄@SiO₂@Cu₃(BTC)₂, was synthesized via an in situ method using Fe(NO₃)₃, Ni(NO₃)₂, CuN₂O₆, TEOS, (3-aminopropyl)triethoxysilane, and benzene-1,3,5-tricarboxylic acid. Three different samples were fabricated according to a formula; xNiFe₂O₄@(100 − x)SiO₂@Cu₃(BTC)₂, where x = 10, 30, and 50. The integration of the intrinsic characteristic of Cu₃(BTC)₂ as an MOF with strong magnetic properties of NiFe₂O₄ could lead to an exquisite material with specific behaviors. X-ray diffraction (XRD), Fourier transform infrared (FTIR), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET), diffuse reflectance spectroscopy (DRS), photoluminescence (PL), vibrating sample magnetometer (VSM), transmission electron microscopy (TEM), and simulated thermal analyzer (STA) were utilized to characterize the mentioned samples. Results approved that the synthesized compounds were composed of SiO₂ and Cu-MOF and NiFe₂O₄ crystalline phases with rod-like morphology. The similarity between the morphology of the synthesized samples and Cu-MOF approved that an appropriate fabrication method has been selected. This fact led to observe mesoporous composites with 38–90 m² g⁻¹ specific surface area. PL spectroscopy confirmed the near bandgap emission, ligand-to-metal charge transfer, and metal-to-ligand charge transfer. Although all the samples had magnetic hysteresis, the highest magnetization was seen in the 50NiFe₂O₄@SiO₂@Cu₃(BTC)₂ sample. This composite compound with a magnetization value of 2 emu g⁻¹ at 8000 Oe and a specific surface area of 90 m² g⁻¹ could be classified as a magnetic MOF (MMOF). STA results suggested that 400°C is the highest operating temperature for this compound.     

Gum Tragacanth (GT): A Versatile Biocompatible Material beyond Borders

The use of naturally occurring materials in biomedicine has been increasingly attracting the researchers’ interest and, in this regard, gum tragacanth (GT) is recently showing great promise as a therapeutic substance in tissue engineering and regenerative medicine. As a polysaccharide, GT can be easily extracted from the stems and branches of various species of Astragalus. This anionic polymer is known to be a biodegradable, non-allergenic, non-toxic, and non-carcinogenic material. The stability against microbial, heat and acid degradation has made GT an attractive material not only in industrial settings (e.g., food packaging) but also in biomedical approaches (e.g., drug delivery). Over time, GT has been shown to be a useful reagent in the formation and stabilization of metal nanoparticles in the context of green chemistry. With the advent of tissue engineering, GT has also been utilized for the fabrication of three-dimensional (3D) scaffolds applied for both hard and soft tissue healing strategies. However, more research is needed for defining GT applicability in the future of biomedical engineering. On this object, the present review aims to provide a state-of-the-art overview of GT in biomedicine and tries to open new horizons in the field based on its inherent characteristics.     

Probing the Nature of the Cluster Effect Observed with Synthetic Multivalent Galactosides and Peanut Agglutinin Lectin

We designed a set of multi‐galactosides with valencies ranging from one to seven and different spacer‐arm lengths. The compounds display a high structural homology for a strict assessment of multivalent phenomena. The multimers were first evaluated by an enzyme‐linked lectin assay (ELLA) toward the peanut agglutinin (PNA). The binding affinity was shown to be dependent on the spacer‐arm length, and cluster effects were observed for the galactosides bearing the shortest and the longest linkers. The latter compounds were shown to be much more potent PNA cross‐linkers in a “sandwich assay”. Dynamic light scattering (DLS) experiments also revealed the formation of soluble aggregates between heptavalent derivatives with medium or long linkers and the labeled PNA. ELLA experiments performed with valency‐controlled clusters and labeled lectins are therefore not always devoid from aggregative processes. The precise nature of the multivalent interaction observed by ELLA for the compounds bearing the shortest linkers, which are unable to form PNA aggregates, was further investigated by atomic force microscopy (AFM). The galactosides were grafted onto the tip of a cantilever and the PNA lectin onto a gold surface. Similar unbinding forces were registered when the valency of the ligands was increased, thus showing that the multimers cannot interact more strongly with PNA. Multiple binding events to the PNA were also never observed, thus confirming that a chelate binding mode does not operate with the multivalent galactosides, probably because the linkers are too short. Altogether, these results suggest that the cluster effect that operates in ELLA with the multimers is not related to additional PNA stabilizations and can be ascribed to local concentration effects that favor a dynamic turnover of the tethered galactosides in the PNA binding sites.     

Matrix‐grafted multiwalled carbon nanotubes/poly(methyl methacrylate) nanocomposites synthesized by in situ RAFT polymerization: A kinetic study

A new approach was developed to functionalize multiwalled carbon nanotubes (MWCNTs) with a polymerizable methyl methacrylate (MMA) groups, and the structure of functionalized MWCNTs were characterized by FTIR, Raman, XPS, and TEM. Using the strategy of “grafting through,” poly(methyl methacrylate) (PMMA) chains were grafted onto the surface of MWCNTs during the in situ synthesis of MWCNT/PMMA nanocomposites over reversible addition‐fragmentation chain transfer (RAFT) polymerization. Kinetics of RAFT‐mediated polymerization of MMA in the presence of MMA‐grafted MWCNTs was studied by using gas chromatography and gel permeation chromatography. To further study, attached polymers were detached and their molecular characteristics were compared to freely formed chains. Results of kinetic studies showed that the utilized commercial chain transfer agent strictly reduced the rate of polymerization as well as relatively controlled molecular weights and narrow molecular weight distributions of free chains. MWCNTs showed a radical activity, retarding the polymerization and reducing the rate of reaction. The effect of MWCNTs concentrations on molecular weights and polydispersity indexes (PDI) was different at the surface and in the bulk. The molecular weights of free chains increased, and the PDI was decreased with increasing MWCNTs. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 555–569, 2012     

Operators with normal Aluthge transforms

The main purpose of the Note is to show that if the second Aluthge transform of an invertible operator is normal, so it is its first Aluthge transform. This extends results due to Moslehian and Nabavi Sales [Some conditions implying normality of operators, C. R. Math. Acad. Sci. Paris, Ser. I 349 (2011) 251–254] and Rose and Spitkovsky [On the stabilization of the Aluthge sequence, International Journal of Information and Systems Sciences 4 (1) (2008) 178–189]. Also, the structure of an injective operator with normal Aluthge transform is studied.