A green approach for the electroorganic synthesis of 2-[(4-methyl-2-pyridyl)amino]-1,4-benzenediol derivatives in aqueous solution

The electrochemical synthesis of some new 2-[(4-methyl-2-pyridyl)amino)-1,4-benzenediol derivatives was performed via the electrochemical oxidation of hydroquinones in the presence of 2-amino-4-methylpyridine in an aqueous solution. The results demonstrate that electrogenerated p-benzoquinone participated in the Michael-type addition reaction via an electrochemical–chemical (EC) reaction mechanism pathway and converted to the corresponding 2-[(4-methyl-2-pyridyl)amino)-1,4-benzenediol derivatives. These new compounds have been synthesized in high yields and purity without using any toxic reagents or catalyst at the surface of carbon electrode.     

Synthesis and structural characterization for novel mixed-donor ligand palladium (II) based on graphene and oxime: its application as a highly stable and efficient recyclable catalyst

In this article, the palladium (II) mixed-ligand complex synthesized with reduced graphene oxides containing tetraethoxysilane and menthone oxime was used as an efficient solid catalyst for the Heck coupling reaction. To maintain stability and catalytic activity in the C–C bond reaction, graphene was considered due to the available surface as the solid support. Then, the structure of new heterogeneous catalyst was investigated by FT-IR, UV–Vis DRS, FE-SEM, EDX, AFM, XRD, ICP-OES, Raman, and TGA. The newly synthesized nanocatalyst have beneficial properties, including product’s easy separation, the shorter time to react, purity products (yield 79–99%), and easier work-up procedure. Furthermore, the catalyst was reused six times without significant degradation in catalytic activity and performance.     

Introducing Fe2+ into Nickel–Iron Layered Double Hydroxide: Local Structure Modulated Water Oxidation Activity

Exploring materials with regulated local structures and understanding how the atomic motifs govern the reactivity and durability of catalysts are a critical challenge for designing advanced catalysts. Herein we report the tuning of the local atomic structure of nickel–iron layered double hydroxides (NiFe‐LDHs) by partially substituting Ni²⁺ with Fe²⁺ to introduce Fe‐O‐Fe moieties. These Fe²⁺‐containing NiFe‐LDHs exhibit enhanced oxygen evolution reaction (OER) activity with an ultralow overpotential of 195 mV at the current density of 10 mA cm^?2, which is among the best OER catalytic performance to date. In‐situ X‐ray absorption, Raman, and electrochemical analysis jointly reveal that the Fe‐O‐Fe motifs could stabilize high‐valent metal sites at low overpotentials, thereby enhancing the OER activity. These results reveal the importance of tuning the local atomic structure for designing high efficiency electrocatalysts.     

Stereocontrolled access to isoprostanes via a bicyclo[3.3.0]octene framework

We report a simple and highly stereocontrolled strategy toward the total synthesis of isoprostanes based on a bicyclic alpha,beta-epoxy ketone intermediate 6. Bicyclo[3.3.0]octene scaffold permitted stereodirection of reagents allowing stereoselective epoxidation, diastereoselective ketone reduction, and regioselective epoxide opening otherwise not accessible with a simple cyclopentene framework.     

Crosstalk between Hepatic Glutathione Efflux and Tumor Targeting Efficiency of Indocyanine Green-Conjugated Gold Nanoparticles

The elevated glutathione (GSH) level in solid tumors has been used as a major hallmark for GSH-responsive nanoparticles to enhance targeting efficiency and specificity. Meanwhile, GSH is mainly synthesized inside the hepatocytes of the liver in the body and constantly released into the blood through hepatic GSH efflux to regulate redox potential of the entire body. However, it remains largely unknown how this hepatic GSH efflux affects the tumor targeting of GSH-responsive nanoparticles. Herein, we report that depletion of hepatic GSH enhanced the tumor targeting of GSH-responsive indocyanine green-conjugated Au₂₅ nanoclusters coated with 18 GSH ligand (ICG-Au₂₅SG₁₈). The dissociation of ICG from Au₂₅SG₁₈ by the hepatic GSH through thiol-exchange reaction and the subsequent hepatobiliary clearance of the detached ICG were slowed down by GSH depletion, which in turn prolonged the blood circulation of intact ICG-Au₂₅SG₁₈ and enhanced its tumor targeting. Our work highlights glutathione-mediated crosstalk between the liver and tumor, in addition to well-known Kupffer cell-mediated uptake, in the tumor targeting of engineered nanoparticles, which could be modulated to enhance targeting efficiency and specificity of cancer nanomedicines while reducing their nonspecific accumulation.     

Steroids contents in waters of wastewater purification plants: determination with partial-filling micellar electrokinetic capillary chromatography and UV detection

Partial-filling micellar electrokinetic capillary chromatography (PF-MEKC) with UV detection was applied for determination of human-based steroids in water samples of Finnish wastewater treatment plants. The samples were purified with solid-phase extraction (SPE) on octadecyl substituted polymer sorbents obtaining analyte enrichment of 20,000-fold. The steroids studied were androgens, estrogens, and progesterone. Three of the steroids could be quantified with the PF-MEKC method. The detection and quantification limits were 0.05–1.06 μg/mL and 0.15–3.2 μg/mL, meaning in the SPE concentrates as 2.5–53 pg/L and 7.5–160 pg/L, respectively. In the influent waters, the total amount of testosterone glucuronide, androstenedione, and progesterone was up to 350 ng/L. In effluent water samples the total steroid quantity was maximum at 320 ng/L. Remarkably high quantity of androstenedione was quantified in both influent and effluent water samples. The cleanest effluent waters were produced in Western Finland. Correspondingly, the highest quantities were located near the largest lake and river areas in South-Eastern Finland. The concentration variation in effluent waters was explained with differences in the purification materials and processes at the plants and with steroid adsorption on soil and organic material suspended into water.     

Efficient and selective oxidation of alcohols with <Emphasis Type="Italic">tert</Emphasis>-BuOOH catalyzed by a dioxomolybdenum(VI) Schiff base complex under organic solvent-free conditions

The catalytic activity of dioxidobis{2-[(E)-p-tolyliminomethyl]phenolato}molybdenum(VI) complex was studied, for the first time, in the selective oxidation of various primary and secondary alcohols using tert-BuOOH as oxidant under organic solvent-free conditions at room temperature. The effect of different solvents was studied in the oxidation of benzyl alcohol in this catalytic system. It was found that, under organic solvent-free conditions, the catalyst oxidized various primary and secondary alcohols to their corresponding aldehyde or ketone derivatives with high yield. The effects of other parameters such as oxidant and amount of catalyst were also investigated. Among different oxidants such as H₂O₂, NaIO₄, tert-BuOOH, and H₂O₂/urea, tert-BuOOH was selected as oxygen donor in the oxidation of benzyl alcohol. Also, it was found that oxidation of benzyl alcohol required 0.02 mmol catalyst for completion. Dioxomolybdenum(VI) Schiff base complex exhibited good catalytic activity in the oxidation of alcohols with tert-BuOOH under mild conditions. In this catalytic system, different primary alcohols gave the corresponding aldehydes in good yields without further oxidation to carboxylic acids.     

Comparative study of the water oxidizing reactions and the millisecond delayed chlorophyll fluorescence in photosystem II at different pH

Water splitting activity, the multiline EPR signal associated with S(2)-state of the CaMn(4)-cluster and the fast and slow phases of the induction curve of the millisecond delayed chlorophyll fluorescence from photosystem II (PSII) in the pH range of 4.5-8.5 were studied in the thylakoid membranes and purified PSII particles. It has been found that O(2) evolution and the multiline EPR signal were inhibited at acidic (pK approximately 5.3) and alkaline (pK approximately 8.1) pH values, and were maximal at pH 6.0-7.0. Our results indicate that the loss of O(2) evolution and the S(2)-state multiline EPR signal associated with the decrease of the millisecond delayed chlorophyll fluorescence only in alkaline region (pH 7.0-8.5). Possible correlations of the millisecond delayed chlorophyll fluorescence components with the donor side reactions in PSII are discussed.     

Operators Defined on n-Modular Spaces

In this paper we study the operators defined between n-modular spaces. In particular, compact operators are studied and then given some applications to fixed points.     

Iridoid glucosides from the aerial parts of Globularia alypum L. (Globulariaceae)

From the hydromethanolic extract of the aerial parts of Globularia alypum grown in Morocco, a new chlorinated iridoid glucoside, globularioside has been isolated beside 5 known iridoid glycosides, globularin, globularicisin, globularidin, globularinin and globularimin. This is the first report of a chlorinated iridoid in G. alypum and in the Globulareaceae. Unlike all other known 7-chlorinated iridoid glucosides where the chlorine atom exhibits an alpha configuration, globularioside incorporate the chlorine atom as a 7beta substituent. The structures of the isolated compounds were established on the basis of ESI-MS, MS-MS, 1D and 2D NMR spectral analysis.