Mechanistic investigations with Bromamine-T: Kinetics of oxidation of thiocyanate ion

The kinetics of oxidation of thiocyanate ion by Bromamine-T (BAT) has been investigated in alkaline medium. The rate of reaction is first order in [OH^–] and zero order in [NCS^–]. The pseudo-first order rate constants decrease with increase in [BAT]. Addition of the reaction products p-toluenesulfonamide, Br^– and neutral salts has no significant effect on the rate. The rate increases with either increase in ionic strength or decrease in dielectric constant of the medium. The activation parameters have been computed. A mechanism consistent with the experimental results has been proposed and the rate law derived. The rate constants predicted from the rate law for the variation of [BAT] are in excellent agreement with the observed rate constants.

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- (BAT) . [OH^–] [NCS^–]. [BAT]. -, Br^– . . . , , . , , [BAT]_o, .

     

Thermal and photochemical transformations of tetraphenyl-p-dioxin and tetraphenyl-p-dithiin

The thermal transformation of tetraphenyl-p-dioxin (1) to 2, 2, 3, 4-tetraphenylbut-3-enolide (5) has been shown to proceed through the intermediacy of cisdibenzoylstilbene (6) and a reasonable mechanism for this transformation has been suggested. The photolysis of tetraphenyl-p-dioxin, on the other hand, has been found to give a mixture of products consisting of mainly benzil and small amounts of tolan. Thermolysis and photolysis of tetraphenyl-p-dithiin (31) follow a different pathway giving rise to tetraphenylthiophene, in each case. The photo-oxygenation of tetraphenyl-p-dithiin, on the other hand, gave a mixture of products consisting of, tetraphenylthiophene, benzil and benzoic acid.     

Effect of Chemical Charging/Discharging on Plasmonic Behavior of Silver Metal Nanoparticles Prepared using Citrate‐Stabilized Cadmium Selenide Quantum Dots

The thermodynamics and kinetics of the chemical and electrochemical charging of a catalyst surface are very important to understand its applicability as a catalyst material, particularly in redox catalysis. Through the present study, we hereby communicate the results obtained from our detailed investigations related to the effect of chemical charging on the plasmonic behavior of silver metal nanoparticles (Ag MNPs) as redox catalysts. Two different batches of Ag MNPs were prepared through thermally assisted chemical reduction of silver ions. The difference in these batches was the use or not of citrate‐capped cadmium selenide quantum dots (Q‐CdSe) for the reduction of solution‐phase silver ions to their colloidal plasmonic phase. The charge on the surfaces of the Ag MNPs was varied by the chemical electron injection method by using BH₄^? ions from a NaBH₄ solution. The processes of charging and discharging were monitored by using UV/Vis absorption spectroscopy. The impact of the concentration of the reductant on the charging and discharging processes was also investigated. The Ag MNPs were also tested for their voltammetric response, wherein it was observed that it was more difficult to oxidize the Ag MNPs prepared with Q‐CdSe seeds than to oxidize Ag MNPs prepared without Q‐CdSe particles. Our results demonstrate that Q‐CdSe seeds not only enhance the redox catalytic activity of Ag MNPs but also provide stability towards polarization of their plasmonic behavior.     

Optically injected spin currents in semiconductors

We show that quantum interference of one and two photon absorption from a two color field allows one to optically inject ballistic spin currents in unbiased semiconductors. The spin currents can be generated with or without an accompanying electrical current and can be controlled using the relative phase of the two colors. We characterize the injected spin currents using symmetry arguments and an eight-band Kane model.     

Synthesis and In Vitro Anticancer Activity of Triazolyl Analogs of Podophyllotoxin,a Naturally Occurring Lignin

Russian Journal of Organic Chemistry - A series of triazolyl-modified podophyllotoxin analogs have been designed and synthesized by utilizing Huisgen 1,3-dipolar cycloaddition in order to develop...     

Design and Synthesis of Non-Covalent Imidazo[1,2-a]quinoxaline-Based Inhibitors of EGFR and Their Anti-Cancer Assessment

A series of 30 non-covalent imidazo[1,2-a]quinoxaline-based inhibitors of epidermal growth factor receptor (EGFR) were designed and synthesized. EGFR inhibitory assessment (against wild type) data of compounds revealed 6b, 7h, 7j, 9a and 9c as potent EGFR^WT inhibitors with IC₅₀ values of 211.22, 222.21, 193.18, 223.32 and 221.53 nM, respectively, which were comparable to erlotinib (221.03 nM), a positive control. Furthermore, compounds exhibited excellent antiproliferative activity when tested against cancer cell lines harboring EGFR^WT; A549, a non-small cell lung cancer (NSCLC), HCT-116 (colon), MDA-MB-231 (breast) and gefitinib-resistant NSCLC cell line H1975 harboring EGFR^L858R/T790M. In particular, compound 6b demonstrated significant inhibitory potential against gefitinib-resistant H1975 cells (IC₅₀ = 3.65 μM) as compared to gefitinib (IC₅₀ > 20 μM). Moreover, molecular docking disclosed the binding mode of the 6b to the domain of EGFR (wild type and mutant type), indicating the basis of inhibition. Furthermore, its effects on redox modulation, mitochondrial membrane potential, cell cycle analysis and cell death mode in A549 lung cancer cells were also reported.