Journal of Chemical Sciences最新文献

Three new palladium(II)-iminophosphine complexes, [Pd(L1)(Cl)₂] C1, [Pd(L2)(Cl)₂] C2 and [Pd(L3)(Cl)₂] C3 have been synthesized and successfully characterized by using ¹H-NMR, ¹³C-NMR, ³¹P-NMR, UV–Vis, FT-IR and magnetic susceptibility techniques. Catalytic activities of complexes towards Suzuki–Miyaura C–C coupling reactions between phenylboronic acid and several aryl halides were investigated under several reaction conditions (solvent, temperature, base, reaction time, and type of substrate). Under optimum conditions, achieving high yields of up to 99% was possible. When 1-bromo-4-nitrobenzene was used for complex C1, bromobenzene for complex C2, and bromobenzene for complex C3, product yields of 99, 99, and 98% were achieved, respectively.

Graphical abstract

Three new palladium complexes bearing iminophosphine ligands was synthesized and successfully characterized. Catalytic activities of the synthesized complexes were investigated on Suzuki–Myaura type coupling reaction between phenylboronic acid and several aryl halides. All complexes exhibited good catalytic activities on C–C coupling reactions up to 99% product formations under mild conditions.

Enzymes are biological catalysts that accelerate chemical reactions by reducing their activation energy. Enzymes specific environmental conditions to function optimally. Additive molecules and compounds, such as organic solvents, ionic liquids, and deep eutectic solvents, have crucial effects on enzyme behavior by changing activity and stability. However, finding and testing different additives is an expensive process that requires specialists, laboratory equipment, and chemical compounds. Machine learning, which has been present in all fields of science and technology in recent years, is one of the ways to find a suitable additive for our desired enzyme without doing a time-consuming experimental process. In this manuscript, we introduce ADDZYME, a machine learning-based software, to predict the effect of additives on enzyme activity. ADDZYME utilizes an ensemble of extremely randomized trees models alongside physicochemical descriptors to make a prediction. To ease usage, ADDZYME is accompanied by a graphical user interface. ADDZYME is freely available on www.github.com/miladrayka/addzyme for further experiments.

Graphical abstract

SYNOPSIS: ADDZYME software applies a machine-learning algorithm to predict the effect of an additive on an enzyme activity. ADDZYME utilizes an ensemble of extremely randomized trees models alongside physicochemical descriptors to make a prediction.

Ammonia (NH₃) is a pyramidal symmetric top molecule with inversion motion and it exists in two distinct nuclear spin isomeric forms, ortho-NH₃ (K = 3n) and para-NH₃ (K ≠ 3n). Here, a pair of electric dipole-allowed [^RQ(4,3) and ^PP(2,2)] and weak forbidden [^OP(3,3) and ^SQ(8,1)] transitions of gas-phase NH₃ were probed in the ν₄ fundamental vibrational band occurring at 6.2 µm mid-IR interference-free spectral region using an external-cavity quantum cascade laser coupled cavity ring-down spectrometer. We have experimentally achieved the ortho-to-para ratio (OPR) of (1.03 ± 0.24) and (1.08 ± 0.14) at room temperature (296 K) for the allowed and forbidden transitions of NH₃, respectively. Furthermore, our experimental findings confirm that the nuclear spin-symmetry is conserved under the nonreactive perturber-induced collisional processes. This study paves the way to directly probe the nuclear spin-isomers of gas-phase NH₃ and thus may lead to an in-depth understanding of nuclear spin-isomerism associated with various physical and chemical processes.

Graphical Abstract

This work shows the high-resolution probing of ortho- and para-nuclear spin-isomers of NH₃ in the gas phase at room temperature using quantum cascade laser coupled cavity ring-down spectroscopy at 6.2 µm mid-IR spectral region.

Sodium borohydride induces the oxidative expansion of the imine derived from isatin and phenylethylamine to form 3-phenethylquinazoline-2,4(1H,3H)-dione. It has been proposed that this transformation occurs by in situ formation of hydroperoxyl anions by a reaction between sodium borohydride and atmospheric oxygen. To contribute to understanding this oxidative expansion, the reaction between the imine derived from isatin and phenylethylamine with hydrogen peroxide was studied in this work. From this reaction, 3-phenethylquinazoline-2,4(1H,3H)-dione was isolated and two by-products were identified: N-phenethyl-2-(3-phenethyl-ureido)-benzamide and methyl(2-(phenethylcarbamoyl)phenyl)carbamate. This article analyses the structure of these by-products and proposes a mechanism that explains the reaction.

Graphical abstract

It was established that the reaction of the imine derived from isatin and phenylethylamine with hydrogen peroxide produces a mixture of three compounds: 3-phenethylquinazoline-2,4(1H,3H)-dione, N-phenethyl-2-(3-phenethyl-ureido)-benzamide and methyl(2-(phenethylcarbamoyl)phenyl)carbamate. A reaction mechanism is proposed that explains this behaviour

Cucurbit[n]urils (CB[n], n = 5–8) are the most important class of host molecules that are widely applied in various important applications. Until now, no sensitive sensor has been developed exclusively for detecting cucurbiturils. Here, we have utilized the supramolecular assembly of acriflavine and graphene oxide (ACF-GO) as a fluorescence sensor for the detection of cucurbituril family members such as CB[5], CB[6] and CB[7] with the discrimination of fluorescence intensities. Among them, CB[7] displayed the highest sensitivity, which can be detected as low as nano-molar concentration, and that allowed us to make a facile fluorescence method of detection for CB[7] and other CBs.

Graphical abstract

Supramolecular assembly of acriflavine on the graphene oxide turn-off the fluorescence of acriflavine and upon interaction with cucurbit[7]uril, that released the acriflavine to the solution and turn-on the fluorescence, which allowed to detect the CB[7] to the lowest of nano-molar concentration.

This work delves into the utility of chromium’s X-ray fluorescence (XRF) lines for the analysis of chromite ores, employing a wavelength-dispersive XRF spectrometer. The CrLα_1,2 and CrLβ₁ fluorescence lines, despite not involving electronic transitions from valence to K-core shell, offer substantial insights into the valence state of chromium. This study examines these relatively unexplored but potentially valuable lines and compares them with the CrKβ series fluorescence lines. Intriguingly, our investigation reveals striking differences in the L-line fluorescence spectra between metallic chromium (Cr(0)), chromite ores (Fe, Mg)Cr₂O₄, and K₂Cr₂O₇. Chemical shifts and peak shapes emerge as key discriminators, surpassing the sensitivity of the CrKβ_1,3 lines. Notably, the chemical shifts of L-lines are amplified, showcasing a clear trend: Cr(III) exhibits a larger shift than Cr(VI), mirroring the pattern observed in the Kβ-lines. The fluorescence peak shapes of Lα_1,2 and Lβ₁ for metallic chromium and chromite ores (both have unpaired 3d-electrons) are similar, whereas those of K₂Cr₂O₇ differ considerably in peak shape, indicating that unpaired 3d-electrons influence these peaks. A linear relationship was found between the area under the curve ratio for Lα_1,2 and Lβ₁ and the valence state of chromium.

Graphical Abstract

Herein, we report the novel protocol for synthesizing bimetallic gold and palladium nanoparticles decorated on rigid and stable cerium oxide support using aloe vera extract. The Au–Pd@CeO₂ catalyst was found to be effective for the Buchwald–Hartwig C–N cross-coupling reaction and amination of benzyl alcohol due to the synergistic influence generated by Au and Pd metals. The prepared catalyst was characterized by using XRD, TEM, SEM, and EDS. The catalyst can be efficiently used for a diverse range of substrates in the Buchwald–Hartwig C–N cross-coupling and amination of benzyl alcohol reactions compared to previously described protocols. The catalyst retains its catalytic activity even after seven cycles.

Graphical abstract

The synthesis of bimetallic gold and palladium nanoparticles decorated on cerium oxide support using aloe vera extract. The Au-Pd@CeO₂ catalyst was found to be effective for Buchwald–Hartwig C-N cross-coupling and amination of benzyl alcohol reactions due to the synergistic effect generated by Au and Pd metals.