Markovnikov versus anti‐Markovnikov addition and C–H activation: Pd–Cu synergistic catalysis

Copper‐ and palladium‐mediated transmetalation and coupling reactions are the backbone to several synthetic methodologies in organic chemistry for C–C bond formation. Computer‐aided simulations using density functional theory (DFT) (B3LYP‐D3 functional with 6‐31G** and effective core potential (ECP)‐LACVP** for heavy atoms for optimizations and cc‐pVTZ(?f) and ECP‐LACV3P** for single‐point calculations) was used to shed light on the probable mechanism of a novel synergistic Cu/Pd catalysts for the coupling of alkene, (Bpin)2 (where, pin = pinacolate), and vinyl‐ or aryl‐halogenated analogues. Every single conceivable pathway was carefully contemplated, and the base minimum energy pathway was found effectively. The copper‐catalyzed nucleophilic generation yields anti‐Markovnikov product using styrene as an alkene. This study affirms quantitatively and accurately how the reaction proceeds and at which steps of the synergistic catalysis the demand of the transmetalation and nucleophile formation for the C–C coupling using phosphine ligands arise. We conclude that the E and Z selectivity depends on the stereochemistry of the substrates used.     

Impact broadening and shift of thallium two-photon transition 6P 1/2–9P 1/2,3/2 perturbed by argon and helium

Summary This paper reports pressure broadening and shift coefficients of thallium 6P–9P _1/2,3/2 transitions by Ar and He as perturbers. Two-photon absorption Doppler free technique has been adopted. The perturing pressure ranges from 300 Torr to 7 atm at 978 K. The red-shift due to Ar and the blue-shift due to He are found to vary linearly with pressure. The Van der Waals constants for these transitions are also reported.

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Riassunto Questo lavoro tratta dell’aumento di pressione e dei coefficienti di spostamento delle transizioni 6P–9P _1/2,3/2 con Ar e He come perturbatori. è stata adottata una tecnica libera Doppler di adsorbimento a due fotoni. La pressione che perturba varia da 300 Torr a 7 atm a 978 K. Si trova che lo spostamento verso il rosso dovuto ad Ar e lo spostamento verso il blu dovuto ad He variano liberamente con la pressione. Si presentano anche le costanti di Van der Waals per queste transizioni.

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Резюме В этой статье исследуются коэффициенты уширения под действием давления и сдвига для переходов 6P–9P _1/2,3/2 в таллии, возмущенном Ar и He. Используется техника двух-фотонного поглощения. Рассматриваются давления от 300 торр до 7 атм при 978 К. Получено, что красный сдвиг, обусловленный Ar, и голубой сдвиг, обусловленный, He, изменяются линейно с давлением. Определяются постоянные Ван дер Ваальса для этих переходов.

     

Density of quarks in heavy spherical nuclei using NRQSM

A nonrelativistic quark shell model (NRQSM) is used to derive an expression for the density of quarks in heavy spherical nuclei. It is shown that quark density is related in a simple way with the probability of finding a nucleon in a nucleus. The quark density is used to determine the ratio of average distance between two quarks to the average distance between two nucleons.     

A study of the variable moment of inertia models

The variable moment of inertia (VMI) model proposed by Holmberg and Lipas has been shown to be a special case of the VMI model of Mariscottiet al. The solution of Mariscotti’s model is expressed in terms of hypergeometric functions, which directly give the rotational energies or their expansions in terms of the quantityF(F+1), whereF is the total angular momentum. The present way of looking at the VMI model also tells us how to write the general dependence of the vibrational energy and the moment of inertia on the energyE _J.     

Antioxidant,cholinesterase inhibition activities and essential oil analysis of Nelumbo nucifera seeds

Nelumbo nucifera seeds’ essential oil (EO), crude extract and subsequent fractions were evaluated for their DPPH, ABTS and superoxide anion-free radical scavenging and cholinesterase inhibitory activities. The ethyl acetate fraction and EO showed outstanding antioxidant activities with IC₅₀ values of 191, 450 μg/mL (DPPH), 123, 221 μg/mL (ABTS) and 69, 370 μg/mL (superoxide anion). The ethyl acetate fraction and EO also caused significant inhibition of acetylcholinesterase and butyrylcholinesterase with IC₅₀ values of 70 ± 0.6, 64 ± 0.8 and 75 ± 0.3, 58 ± 0.2, in dose-dependent manner. The first ever gas chromatography–mass spectrometry analysis of the EO obtained from N. nucifera seeds resulted in identification of 19 constituents, mainly comprised of oxygenated sesquiterpenes responsible for their promising bioactivity. The crude and fractions revealed the presence of saponins, flavonoids, steroids, alkaloids, terpenoids and cardiac glycosides in phytochemical investigation.     

Simultaneous determination of potassium clavulanate and cefixime in synthetic mixtures by high-performance liquid chromatography

A simple, precise, and sensitive high-performance liquid chromatographic method was developed and validated for the simultaneous determination of potassium clavulanate and cefixime in synthetic mixture form. The analytes were separated on a C18 column by using 0.03 M disodium hydrogen phosphate buffer (pH 6.5)-methanol (84 + 16, v/v) as the mobile phase with detection at 220 nm. The method exhibited high sensitivity and good linearity in the concentration ranges of 12.5-62.5 and 20-100 microg/mL for potassium clavulanate and cefixime, respectively. The total run time for the 2 components was <8 min, and the average recovery was >101.5% with a relative standard deviation of <1.0%. The proposed method was validated according to guidelines of the International Conference on Harmonization by evaluation of linearity, recovery, selectivity, robustness, limits of detection and quantitation, and within- and between-day precision. The results obtained for the synthetic mixture show that the method is highly precise and accurate for the simultaneous determination of potassium clavulanate and cefixime.     

Pt3Co Octapods as Superior Catalysts of CO2 Hydrogenation

As the electron transfer to CO₂ is a critical step in the activation of CO₂, it is of significant importance to engineer the electronic properties of CO₂ hydrogenation catalysts to enhance their activity. Herein, we prepared Pt₃Co nanocrystals with improved catalytic performance towards CO₂ hydrogenation to methanol. Pt₃Co octapods, Pt₃Co nanocubes, Pt octapods, and Pt nanocubes were tested, and the Pt₃Co octapods achieved the best catalytic activity. Both the presence of multiple sharp tips and charge transfer between Pt and Co enabled the accumulation of negative charges on the Pt atoms in the vertices of the Pt₃Co octapods. Moreover, infrared reflection absorption spectroscopy confirmed that the high negative charge density at the Pt atoms in the vertices of the Pt₃Co octapods promotes the activation of CO₂ and accordingly enhances the catalytic activity.     

Synthesis of ligand-selective ZnS nanocrystals exhibiting ligand-tunable fluorescence

High-quality ZnS nanocrystals (NCs) of nearly identical size are synthesized using isomeric ligands, o-, m-, p-phenylenediamines (PDAs) that bind to the NC cores. The fluorescence emission from the NC is tunable according to the structure of the isomer. The measured fluorescence quantum yields (QYs) are 2-3 times higher for NCs that are passivated with isomeric PDA ligands than the fluorescence QY of NCs prepared at the absence of PDAs. The NC morphologies were studied by low-angle and wide-angle X-ray diffraction (XRD), and by transmission electron microscopy (TEM). The average correlating sizes were found to be 3.0+/-0.3, 3.7+/-0.30, and 3.0+/-0.5 nm for the NCs that were passivated with o-PDA, m-PDA, and p-PDA, respectively. The Fourier-transform infra-red (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) studies were carried out to investigate the shell structure and the interaction between the core and the shell. The adsorbed ligands were quantitatively analyzed by TGA. The structure, morphology, and optical properties of these PDA passivated NCs were compared with the NCs prepared in the absence of PDA.     

Synthesis of silver nanoparticles using root extract of Duchesnea indica and assessment of its biological activities

Treatment of microbial infections and inflammatory conditions have many challenges in terms of efficacy and safety issues. Novel approaches such as nanoparticles based drug delivery system have shown promising results to solve some of these problems. The aim of this study was to exploit the efficacy of the synthesized silver nanoparticles. In this study, silver nanoparticles (AgNPs) were biosynthesized using root extract (aqueous) of Duchesnea indica. They were characterized using different techniques such as, ultraviolet–visible (UV–Vis) spectrophotometry, transmission and scanning electron microscopy (TEM and SEM), X-ray diffractometer (XRD), energy dispersive X-ray spectroscopy (EDX), fourier-transform infrared spectroscopy (FTIR) and zetasizer. The UV–Vis spectra gave a characteristic peak at 423 nm; XRD confirmed its crystalline structure; FTIR confirmed the involvement of phytochemicals in their capping and reduction; TEM images confirmed their spherical shape with average width of 20.49 nm and average area of 319.25 nm². Various biological activities were performed on these NPs, such as antimicrobial, anti-inflammatory, analgesic and muscle relaxant, which showed significant results as follow. Among bacterial strains, Salmonella typhi (MIC: 0.01 mg/ml) and Escherichia coli (MIC: 0.01 mg/ml), while among that of fungal Microsporum canis (MIC: 0.53 mg/ml) and Alternaria alternata (MIC: 0.51 mg/ml) were most susceptible. The AgNPs showed maximum anti-inflammatory activity (46.15 and 56.85%) at 20 mg/kg after 3 and 5 h of drug administration, comparable to that of standard. In-vivo model exhibited concentration dependent inhibition of both COX-2 and 5-LOX enzymes. Similarly, it exhibited maximum analgesic activity (54.24%) at 20 mg/kg dose after 60 min. of pain induction. Furthermore, they depicted maximum muscle relaxation (P < 0.01) after 60 and 90 min of drug administration. Above results suggest that these AgNPs can be studied further for the development of more effective and safe formulations.