MAu₂GeS₄‑Chalcogel (M = Co, Ni): Heterogeneous Intra- and Intermolecular Hydroamination Catalysts

High surface area macroporous chalcogenide aerogels (chalcogels) MAu₂GeS₄ (M = Co, Ni) were prepared from K₂Au₂GeS₄ precursor and Co­(OAc)₂ or NiCl₂ by one-pot sol–gel metathesis reactions in aqueous media. The MAu₂GeS₄-chalcogels were screened for catalytic intramolecular hydroamination of 4-pentyn-1-amine substrate at different temperatures. 87% and 58% conversion was achieved at 100 °C, using CoAu₂GeS₄- and NiAu₂GeS₄-chalcogels respectively, and the reaction kinetics follows the first order. It was established that the catalytic performance of the aerogels is associated with the M²⁺ centers present in the structure. Intermolecular hydroamination of aniline with 1-R-4-ethynylbenzene (R = −H, −OCH₃, −Br, −F) was carried out at 100 °C using CoAu₂GeS₄-chalcogel catalyst, due to its promising catalytic performance. The CoAu₂GeS₄-chalcogel regioselectively converted the pair of substrates to respective Markovnikov products, (<i>E</i>)-1-(4-R-phenyl)-<i>N</i>-phenylethan-1-imine, with 38% to 60% conversion

Predicting Fuel Ignition Quality Using ¹H NMR Spectroscopy and Multiple Linear Regression

An improved model for the prediction of ignition quality of hydrocarbon fuels has been developed using ¹H nuclear magnetic resonance (NMR) spectroscopy and multiple linear regression (MLR) modeling. Cetane number (CN) and derived cetane number (DCN) of 71 pure hydrocarbons and 54 hydrocarbon blends were utilized as a data set to study the relationship between ignition quality and molecular structure. CN and DCN are functional equivalents and collectively referred to as D/CN, herein. The effect of molecular weight and weight percent of structural parameters such as paraffinic CH₃ groups, paraffinic CH₂ groups, paraffinic CH groups, olefinic CH–CH₂ groups, naphthenic CH–CH₂ groups, and aromatic C–CH groups on D/CN was studied. A particular emphasis on the effect of branching (i.e., methyl substitution) on the D/CN was studied, and a new parameter denoted as the branching index (BI) was introduced to quantify this effect. A new formula was developed to calculate the BI of hydrocarbon fuels using ¹H NMR spectroscopy. Multiple linear regression (MLR) modeling was used to develop an empirical relationship between D/CN and the eight structural parameters. This was then used to predict the DCN of many hydrocarbon fuels. The developed model has a high correlation coefficient (<i>R</i>² = 0.97) and was validated with experimentally measured DCN of twenty-two real fuel mixtures (e.g., gasolines and diesels) and fifty-nine blends of known composition, and the predicted values matched well with the experimental data

Dynamics and Mechanism of Intercalation/De-Intercalation of Rhodamine B during the Polymorphic Transformation of the CdAl Layered Double Hydroxide to the Brucite-like Cadmium Hydroxide

We studied the kinetics of intercalation of a fluorescent probe (rhodamine B (RhB)) during the formation of hierarchal microspheres of cadmium–aluminum layered double hydroxide (CdAlA LDH) and its de-intercalation upon transformation from the LDH phase into the cadmium hydroxide β phase (Cd­(OH)₂) using a reaction-diffusion framework (RDF) where the hydroxide anions diffuse into an agar gel matrix containing the proper salts–fluorescent probe mixture. In this framework, we achieved the stabilization of the CdAlA LDH, which is known to be thermodynamically unstable and transforms into Cd­(OH)₂ and Al­(OH)₃ in a short period. RDF is advantageous as it allows with ease the extraction of the cosynthesized polymorphs and their characterization using X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), solid-state nuclear magnetic resonance (SSNMR), Fourier transform infrared (FT-IR), and energy dispersive X-ray (EDX). The kinetics of inter/de-intercalation is studied using <i>in situ</i> steady-state fluorescence measurements. The existence of RhB between the LDH layers and its expel during the transition into the β phase are examined via fluorescence microscopy, XRD, and SSNMR. The activation energies of intercalation and de-intercalation of RhB are determined and show dependence on the cationic ratio of the corresponding LDH. We find that the energies of de-intercalation are systematically higher than those of intercalation, indicating that the dyes are stabilized due to the probe–brucite sheets interactions. SSNMR is used to shed light on the mechanism of intercalation and stabilization of RhB inside the layers of the LDH

TG/DTG, FT-ICR Mass Spectrometry, and NMR Spectroscopy Study of Heavy Fuel Oil

There is an increasing interest in the comprehensive study of heavy fuel oil (HFO) due to its growing use in furnaces, boilers, marines, and recently in gas turbines. In this work, the thermal combustion characteristics and chemical composition of HFO were investigated using a range of techniques. Thermogravimetric analysis (TGA) was conducted to study the nonisothermal HFO combustion behavior. Chemical characterization of HFO was accomplished using various standard methods in addition to direct infusion atmospheric pressure chemical ionization Fourier transform ion cyclotron resonance mass spectrometry (APCI-FTICR MS), high resolution ¹H nuclear magnetic resonance (NMR), ¹³C NMR, and two-dimensional heteronuclear multiple bond correlation (HMBC) spectroscopy. By analyzing thermogravimetry and differential thermogravimetry (TG/DTG) results, three different reaction regions were identified in the combustion of HFO with air, specifically, low temperature oxidation region (LTO), fuel deposition (FD), and high temperature oxidation (HTO) region. At the high end of the LTO region, a mass transfer resistance (skin effect) was evident. Kinetic analysis in LTO and HTO regions was conducted using two different kinetic models to calculate the apparent activation energy. In both models, HTO activation energies are higher than those for LTO. The FT-ICR MS technique resolved thousands of aromatic and sulfur containing compounds in the HFO sample and provided compositional details for individual molecules of three major class species. The major classes of compounds included species with one sulfur atom (S₁), with two sulfur atoms (S₂), and purely hydrocarbons (HC). The DBE (double bond equivalent) abundance plots established for S₁ and HC provided additional information on their distributions in the HFO sample. The ¹H NMR and ¹³C NMR results revealed that nearly 59% of the ¹H nuclei were distributed as paraffinic CH₂ and 5% were in aromatic groups. Nearly 21% of ¹³C nuclei were distributed in aromatic groups, indicating that most paraffinic CH₂ groups are attached to aromatic rings. A negligible amount of olefins was present, and an appreciable quantity of monoaromatic and polyaromatic content was observed. Molecular connectivity between the hydrogen and carbon atoms using HMBC spectra was utilized to propose several plausible skeletal structures in HFO

Anti-cancer agents in Saudi Arabian herbals revealed by automated high-content imaging

<div><p>Natural products have been used for medical applications since ancient times. Commonly, natural products are structurally complex chemical compounds that efficiently interact with their biological targets, making them useful drug candidates in cancer therapy. Here, we used cell-based phenotypic profiling and image-based high-content screening to study the mode of action and potential cellular targets of plants historically used in Saudi Arabia’s traditional medicine. We compared the cytological profiles of fractions taken from <i>Juniperus phoenicea</i> (Arar), <i>Anastatica hierochuntica</i> (Kaff Maryam), and <i>Citrullus colocynthis</i> (Hanzal) with a set of reference compounds with established modes of action. Cluster analyses of the cytological profiles of the tested compounds suggested that these plants contain possible topoisomerase inhibitors that could be effective in cancer treatment. Using histone H2AX phosphorylation as a marker for DNA damage, we discovered that some of the compounds induced double-strand DNA breaks. Furthermore, chemical analysis of the active fraction isolated from <i>Juniperus phoenicea</i> revealed possible anti-cancer compounds. Our results demonstrate the usefulness of cell-based phenotypic screening of natural products to reveal their biological activities.</p></div

The effect of plant fractions on mitochondrial superoxide production and cell-membrane permeability.

<p><b>A)</b> HeLa cells were treated with plant fractions for 24 h. An increase in the MitoSox signal was detected and correlated with the increasing concentration of the plant fraction. <b>B)</b> HeLa cells were treated with different concentrations of plant fractions for 24 h and then subjected to a cell membrane permeability test. Fluorescence readouts were normalized against an in-plate control. Each sample was tested in quadruplicate. Data are presented as means ± SD.</p

The cytotoxic effect of plant fractions on HeLa cells.

<p>A-B) Cells were treated with various concentrations of plant extracts for 24 h or 48 h, stained with Hoechst, and assessed using HCS. The cells exhibited cytotoxicity, which is indicator of induced apoptosis or necrosis. C) The distribution of cells during the cell cycle: G2/M, S, G0/G1 and low phases after a 24-h treatment with plant fractions. Data shown are means ± SD.</p

Cytological profiling heat map.

<p>Automated HCS was used to assess compound-related perturbations of human cells using a full set of cellular markers. To assign possible biological targets to the test compounds, we compared the resulting cytological profiles to profiles retrieved from reference compounds with known modes of action. Some of the plant fraction extracts closely matched FDA-approved anticancer drugs and clustered with topoisomerase inhibitors. Individual features are presented on the x-axis and individual compounds are presented on the y-axis.</p

Plant fractions induced an apoptotic effect on HeLa cells.

<p>HeLa cells were treated with several concentrations (1.56, 3.12, 6.25, 12.5, 25, and 50 μg/ml) of plant fractions for 24 h or 48 h. A, B) Automated HCS was used to measure the activity of caspase-9 and C, D) p53. The fluorescence readout was normalized against an in-plate control. Each sample was tested in quadruplicate. Data are presented as means ± SD.</p

Assesment of the double-strand breaks in the DNA.

<p>HeLa cells were treated with different concentrations of SPE fractions to detect the expression of γ-H2AX. Data are presented as means ± SD.</p