ZnO–Bentonite nanocomposite: an efficient catalyst for discharge of dyes,phenol and Cr(VI) from water

The present work focused on application of ZnO-NPs@bentonite, as a catalyst, for disposal of different pollutants such as dyes, phenol compounds and Cr(VI) ions from water. The prepared ZnO–bentonite nanocomposite was characterized by using FT-IR, X-ray powder diffraction, and Scanning electron microscopy analysis. The results showed that the amount of zinc oxide influenced the catalytic performance of ZnO–bentonite nanocomposite. Small amounts of zinc oxide on bentonite have a positive effect whereas increase in weight ratios has a negative effect.

     

Review: Inverse coordination. Inorganic open and cyclic nitrogen heteroatom molecules as coordination centers. A survey of molecular topologies

This review is a follow up to a previous article [I. Haiduc J. Coord. Chem. (2018) doi:10.1080/00958972.2018.1515429.] which illustrated the concept of inverse coordination with structures in which the coordination center is nitrogen alone (mono- and poly-nitrogen moieties). Here the open and cyclic heteroatom molecules with inorganic skeletons and nitrogen donor sites are presented. Organic nitrogen heterocycles will be treated in a further review.

     

Two new triterpenoids from Gardenia jasminoides fruits

A new cycloartane triterpenoid, named gardenolic acid C (1), a new ursane triterpenoid, named 3β,16β,21β,23,24-pentahydroxy urs-12,18,20-trien-28-oic acid γ-lactone (2), together with three know triterpenoids, gardenolic acid A (3), gardenolic acid B (4), and 3α,16β,23,24-tetrahydroxy-28-nor-ursane-12,17,19,21-tetraen (5) were isolated from the fruits of Gardenia jasminoides Ellis. The structures of these compounds were elucidated by analyses of spectroscopic data. All isolates were evaluated for their neuroprotective effects in vitro.

     

The role of 8-quinolinyl moieties in tuning the reactivity of palladium(II) complexes: a kinetic and mechanistic study

The rate and mechanism of chloride substitution from Pd(II) complexes, chlorobis-(2-pyridylmethyl)aminepalladium(II), 1, chloro-8-[(2-pyridylmethyl)amino]quinolinepalladium(II), 2, chloro-N-(2-pyridinylmethylene)-8-quinolinaminepalladium(II), 3, and chlorobis(8-quinolinyl)aminepalladium(II), 4, are reported. The labile chloride was substituted from the complexes by thiourea nucleophiles viz, thiourea (Tu), N,N′-dimethylthiourea (Dmtu) and N,N,N′,N′-tetramethylthiourea (Tmtu). The reactions were monitored under pseudo-first-order conditions in methanol using stopped-flow spectrophotometry as a function of concentration and temperature. All the reactions obeyed the rate law k_obs = k₂[Nu] following the order 1 > 3 > 2 > 4 with 4 exhibiting the slowest rate of substitution due to the stronger σ-donor effect of 8-quinolyl moiety of the coordinated ligand, which makes the Pd center more electron-rich. This slows the nucleophilic attack by the nucleophiles. The values of the thermodynamic parameters (ΔH^# and ΔS^#) support an associative substitution mechanism. The trends in the DFT calculated data support the experimentally observed order of the reactivity of the complexes.

     

MgFe2O4@SiO2-PrNH2/Pd/bimenthonoxime core-shell magnetic nanoparticles as a recyclable green catalyst for heterogeneous Suzuki cross-coupling in aqueous ethanol

Magnetically recoverable MgFe₂O₄@SiO₂-PrNH₂/Pd/bimenthonoxime nanoparticles were prepared and characterized by SEM, EDX, TEM, XRD, XPS, ICP, VSM and FT-IR. The nanocatalyst was used for Suzuki cross-coupling in aqueous ethanol media, and the corresponding biaryl derivatives were synthesized within short reaction time. The catalyst was separated by an external magnet and reused several times.

     

Biochemical relevance of Cr(III) complexes of isoniazid: synthesis,characterization, DFT,antibacterial screening,antioxidant activity and glucose-lowering effect in STZ-induced diabetic rats

Molecular mechanism suggests that the incorporation of an antioxidant organic moiety to chromium will be a sound strategy for the synthesis of safer and more effective hypoglycemic compounds. Two Schiff base ligands were derived by condensation of isonicotinyl hydrazide with salicylaldehyde/o-hydroxyacetophenone which further yield four novel chromium(III) complexes of types [Cr(L)Cl₂(H₂O)] and [Cr(L)₂]Cl. The ligands and complexes were characterized by analytical and spectroscopic techniques. DFT study at the basic set B3LYP and TD-SCF/6-311-G level was employed to confirm the geometry of the investigated compounds. Ligands were tested for their antioxidant activity and exhibited good antioxidant activity. Assessment of insulin-like activity of the complexes was initially performed in vitro by measuring the inhibition of α-amylase. The complex with highest in vitro activity was investigated for in vivo antidiabetic activity on the model of STZ-induced diabetic rats, which demonstrated that complex 4 significantly lowers the blood glucose level in rats. Toxicity level and antioxidant activity of the complex were also tested, which exhibit good tolerance level and antioxidant activity. Histological analysis of the pancreas of animals under investigation reveals the good condition of the pancreas treated with the complex. Ligands and complexes were also tested for antibacterial activity against Escherichia coli.

     

Two self-assembled supramolecular solar cells sensitized via axial coordination with zinc porphyrin

In this work, two new self-assemblies based on zinc porphyrins substituted at the meso-positions with different donor units (denoted as ZnP1 and ZnP2) and anchor porphyrin (ZnPA) dyads formed by the coordination bonds of Zn-to-ligand have been prepared. Further, the assemblies were absorbed on semiconducting TiO₂ electrode surfaces by the carboxylic groups of anchor porphyrin (ZnPA), and their photovoltaic performances in solar cells were performed under 100 mW cm^?2 AM 1.5G sunlight. Photoelectrochemical studies reveal a significantly improved photovoltaic behavior for the dyad of triphenylamine-based zinc porphyrin (ZnP1) compared to the dyad with trimethylamine-based zinc porphyrin. The results were verified by electrochemical impedance spectroscopy, calculations, and optical performance. In addition, the modes of the assemblies immobilized on TiO₂ electrode surfaces were also verified by transmission electron microscopy.     

Development of new and robust LC-MS method for simultaneous quantification of polyphenols from Sambucus ebulus fruits

A new and simple LC-MS method for analysis of flavonoids from Sambucus ebulus berry extracts was developed and validated. Successfully were quantitated seven polyphenols: epicatechin, epigallocatechin gallate, rutin, resveratrol, myricetin, quercetin, and kaempferol.

Two detectors, working in parallel, were used: photodiode-array and single quadrupole mass-detector. The mass detection was used for identification and quantification of the analytes, while the diode-array detector was as confirmation tool. The following m/z were tracked: 457.15 (epigallocatechin gallate); 289.06 (epicatechin); 609.13 (rutin); 227.05 (resveratrol); 317.0 (myricetin); 301.02 (quercetin); 285.02 (kaempferol). For optimization the chromatographic separation three wavelengths 205?nm, 305?nm, 272?nm were monitored. The method was capable to detect in one run compounds with no UV or fluorescence chromophore and with very similar structures, such as plant polyphenols. The linearity was from 0.05?mg/L to 50?mg/L (R² 0.9962–0.9987). The recoveries for all tested analytes were between 81.6% and 104.7%.

The method was applied for analysis of crude extract of Sambucus ebulus ripe fruits. Three major polyphenols – epicatechin (0.84?mg/100gFW), quercetin (0.15?mg/100gFW) and kaempferol (0.05?mg/100gFW) were identified and quantified.

The proposed method could be successfully used for routine analysis of epigallocatechin gallate, epicatechin, rutin, resveratrol, myricetin, quercetin, and kaempferol in Sambucus ebulus extracts.     

Crystallographic and DFT studies on host-guest complexes consisting of zinc bisporphyrinates and 1-phenylethylamine

We have investigated the chirality transfer from 1-phenylethylamine to a 5-amino-1,3-phthalic acid diamide-linked zinc bisporphyrinate through crystallographic and DFT studies. When the hosts were mixed with optically pure 1-phenylethylamine, CD showed moderate signals in the Soret band region. Single crystals of the corresponding 1:1 and 1:2 host-guest complexes were obtained. We present the first crystallographic structure of a 1:2 host-guest complex consisting of a bisporphyrin host and chiral monoamine guests. The structure reveals that the host-guest interactions are different for two guest molecules. The first guest is involved in a hydrogen bond and π-π interactions, while the second one is only involved in π-π interactions, which has not been observed in previous studies. The corresponding chirality transfer mechanism was also rationalized by DFT calculations.

     

Synthesis and Characterization of Two New Organic Dyes for Dye-Sensitized Solar Cells

In the present study, two new organic dyes based on indigo were prepared and used as sensitizers in dye-sensitized solar cells. To this end, indoxyl was utilized as the electron-donor and acrylic acid and cyanoacrylic acid were used as the electron-acceptor anchoring groups. These dyes were purified and characterized by analytical techniques. Spectrophotometric evaluations of the prepared dyes in solution and on a nano-anatase-TiO₂ substrate were investigated. Additionally, oxidation potential measurements were also carried out. Finally, dye-sensitized solar cells were fabricated to determine the photovoltaic behavior and conversion efficiency of each dye.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]     

A Computational Study of the S2 State in the Oxygen-Evolving Complex of Photosystem II by Electron Paramagnetic Resonance Spectroscopy

The S₂ state produces two basic electron paramagnetic resonance signal types due to the manganese cluster in oxygen-evolving complex, which are influenced by the solvents, and cryoprotectant added to the photosystem II samples. It is presumed that a single manganese center oxidation occurs on S₁ → S₂ state transition. The S₂ state has readily visible multiline and g4.1 electron paramagnetic resonance signals and hence it has been the most studied of all the Kok cycle intermediates due to the ease of experimental preparation and stability. The S₂ state was studied using electron paramagnetic resonance spectroscopy at X-band frequencies. The aim of this study was to determine the spin states of the g4.1 signal. The multiline signal was observed to arise from a ground state spin ½ centre while the g4.1 signal generated at ≈140 K NIR illumination was proposed to arise from a spin 52 center with rhombic distortion. The ‘ground’ state g4.1 signal was generated solely or by conversion from the multiline. The data analysis methods used involved numerical simulations of the experimental spectra on relevant models of the oxygen-evolving complex cluster. A strong focus in this paper was on the ‘ground’ state g4.1 signal, whether it is a rhombic 52 spin state signal or an axial 32 spin state signal. The data supported an X-band CW-EPR-generated g4.1 signal as originating from a near rhombic spin 5/2 of the S₂ state of the PSII manganese cluster.     

Assembly of polyoxometalate-templated metal-organic framework with effective peroxidase-like catalytic activity

A new polyoxometalate (POM)-templated 3-D copper(II)-triazole framework [Cu₁₀(trz)₁₀(OH)₆(Cl)₄][H₃PW₁₂O₄₀]·2H₂O (trz = 1,2,3-triazole) has been synthesized and characterized by single crystal X-ray diffraction and other routine methods. The 3-D POM/copper(II)-triazole hybrid framework with a 1-D channel possesses a pcu topology under the template of bulk Keggin-type phosphotungstate. As a new kind of peroxidase mimetic, the new compound effectively catalyzed oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of H₂O₂. The electrostatic interactions and hydrogen bonds/π-π stacking interactions among TMB, trz, and phosphotungstate are responsible for the enhancement of peroxidase-like activity. In addition, application for colorimetric sensing of H₂O₂ is also explored; the new compound exhibits a wide linear range (1–80?μM), low detection limit (0.21?μM), and fast response (2?min).

     

Dy(III) complexes of metformin Schiff-bases as glucose probe: synthesis,spectral, and thermal properties

Complexes of Dy³⁺ with metformin-Schiff-bases of salicylaldehyde (HL¹); 2,3-dihydroxybenzaldehyde (H₂L²); 2,4-dihydroxybenzaldehyde (H₂L³); 2,5-dihydroxybenzaldehyde (H₂L⁴); 3,4-dihydroxybenzaldehyde (H₂L⁵); and 2-hydroxynaphthaldehyde (HL⁶) were synthesized by template reactions. The new compounds were characterized through elemental analysis, conductivity and magnetic moment measurements, IR, UV–vis, fluorescence, GC–MS, and XRD spectroscopies. The complexes are seven coordinate with formulas [DyL^1–4,6(NO₃)₂(H₂O)₂]·nH₂O where n?=?2, 2½, 4, 2, 2 and [DyL⁵(NO₃)(H₂O)₄]·2H₂O. TGA, DTG, and DTA analyses confirmed the suggested stereochemistry and subsequently the proposed mechanism of thermal decomposition. Kinetic and thermodynamic parameters were calculated for the second decomposition step. Thus, we report the ability of using the prepared complexes in the detection of glucose at physiological conditions using UV–vis and fluorescence spectroscopy as well as viscosity measurements, where the association constants were calculated.

     

Susceptibly of Alphitobius diaperinus to Beauveria bassiana extracts

Alphitobius diaperinus is an important pathogen with worldwide distribution that causes severe economic loss of efficiency in broilers. This study evaluates the potential of organic extracts of two strains entomopathogenic fungus Beauveria bassiana (CG71 and UNI40) as a biocontrol agent on A. diaperinus and promotes the phytochemical investigation. The effective percentages of mortalities were 95.97% (UNI40 methanolic extract), 69.23, 64.64, and 50.39% (CG 71 methanolic, ethyl acetate and butanol extracts). However, there was a decrease in the lesser mealworms susceptibility in relation to the use of insecticides and extracts. The metabolites 5-hydroxymethyl-2-furanoic acid, dipicolinic acid and monomethyl dipicolinate were isolated from ethyl acetate extract, and β-adenosine of butanolic extract of B. bassiana CG 71. In addition, the cyclodepsipeptides were identified in methanolic extracts of the two strains. The insecticide activity results indicated that the B. bassiana extracts are an alternative to A. diaperinus control.

     

Pd(0) nanoparticles immobilized on multinitrogen functionalized halloysite for promoting Sonogashira reaction: studying the role of the number of surface nitrogens in catalytic performance

Halloysite nanoclay, Hal, was amine-functionalized and subsequently reacted with 2,4,6-trichloro-1,3,5-triazine, TCT, and ethylenediamine, EDA, to provide multinitrogen containing functionality on the surface of Hal. The resulting surface-modified Hal, Hal-2N-TCT-EDA, was then used for immobilization of Pd nanoparticles and affording a heterogeneous catalyst, Pd@Hal-2N-TCT-EDA, with utility for copper and ligand-free Sonogashira coupling of alkynes and aryl halides. The results established the efficiency of this protocol in terms of product yield, ecofriendly nature, and reaction time. Study of the reusability of the catalyst confirmed that the catalyst could be recovered and recycled up to seven times with slight loss of catalytic activity and Pd leaching, indicating the efficiency of Hal-2N-TCT-EDA for embedding Pd nanoparticles. To elucidate the role of the number of surface nitrogens on the catalytic performance, the catalytic activity, and recyclability of the catalyst was compared with those of Hal-2N and Hal-2N-TCT. It was found that more surface nitrogen atoms gave higher loading of Pd and lower Pd leaching. This result confirms the contribution of surface nitrogens to anchor the Pd species and suppress leaching.

     

Immobilization of glucose oxidase based on the sodium alginate-modified products of a functionalized metal organic framework and the application for one-pot analysis of glucose

A self-assembled functionalized metal-organic framework, Zn₄O(NH₂BDC)₃ microcrystalline (IRMOF3) could be prepared by washing complex with DMF and CH₂Cl₂. Via modification with sodium alginate (AA), IRMOF3-AA samples could be obtained. IR and TEM were used for structural confirmation of IRMOF3-AA samples. PEG-GOD could be obtained via PEGylation of glucose oxidase (GOD), which could be confirmed by X-ray photoelectron spectroscopy (XPS) and used for further application. IRMOF3-AA@PEG-GOD samples could be obtained by the immobilization of PEG-GOD to IRMOF3-AA, and the best immobilization condition was achieved by adjusting the amount of GOD. From the view point of enzyme mimics, combined with peroxidase-like properties of the IRMOFS-AA samples, the determination of glucose was demonstrated with a linear range from 5?×?10^?5 mol/L to 1.6?×?10^?3 mol L^?1 using tetramethylbenzidine (TMB) as chromogenic substrate. The prepared IRMOF3-AA@PEG-GOD samples exhibited dual functional enzyme-like (peroxidase and GOD-like) activities, with simple experimental steps.

     

Gas chromatography tandem mass spectrometry for the screening of adulterants in seized captagon™ tablets

Background: Amphetamine type stimulants (ATS) are the second most popular illegal drugs used worldwide, after cannabis. The production of ATS has increased across the world, including the Middle East. Fenethylline (Captagon?), amphetamine derivative, sold as a street drug usually contains several adulterants and diluents. In Saudi Arabia, like other countries, samples of illicit ATS are submitted to laboratories to test for the adulterated compounds.

Objective: The objective of the proposed study was to apply gas chromatography/mass spectrometry (GC/MS) for fenethylline profiling of seized samples collected from the Saudi market (n?=?55).

Methodology: The GC/MS analysis was performed on a general purpose column (30?m?×?0.25?mm i.d) coated with 0.25?µm cross bond, 5% diphenyl dimethyl polysiloxane (Rtx-5MS). The mass was operated in the electron impact mode.

Results and discussion: Analyzed samples gave positive results for amphetamine in the concentration range between 1.35% and 37.32% of the powder, caffeine in the range between 22.74 and 44.92%, in addition to different concentrations of levoglucosenone, theophylline, D-allose, lidocaine, methamphetamine, dextromethorphan, and other adulterants. Finally, the presence of other substances in fenethylline street samples could result in intoxication. This significantly contributes to the potential risk of drug addiction among public.     

Microbial transformation of isocoronarin D by Cunninghamella echinulata NRRL 1386

The diterpene isocoronarin D (1) is a bioactive major constituent of labdane diterpene from the aerial parts of Curcuma comosa Roxb. (Zingiberaceae), the Thai medicinal plant. Microbial transformation of 1 was performed by the fungus Cunninghamella echinulata NRRL 1386 to yield three new metabolites, 3β-hydroxyisocoronarin D (2), 6α-hydroxyisocoronarin D (3) and 3β,7α-dihydroxyisocoronarin D (4). The structures of the new compounds were elucidated by spectroscopic techniques.

     

Four Ni(II), Co(III), Cd(II) complexes based on 5-(pyrazol-1-yl)nicotinic acid: synthesis,X-ray single crystal structure,in vitro cytotoxicity,apoptosis and molecular docking studies

We have developed complexes [Ni₂(L)₂(H₂O)₄]_n (1), [Co₂(L)₂(H₂O)₄]_n (2), [Cd₂(L)₂(H₂O)₂Cl₂]n (3) and [Cd₂(L)₂(H₂O)₂]_n (4), where HL = 5-(pyrazol-1-yl) nicotinic acid. All complexes were characterized by elemental analysis, IR spectroscopy and single crystal X-ray diffraction, showing monoclinic crystal lattice with space group P2₁/c (1), P2₁/c (2), P2₁/c (3), and triclinic crystal lattice with space group P-1 (4), separately. In vitro antitumor screening (MTT method) revealed that 3 exhibited better inhibitory activities than the commercial anticancer drug cisplatin against HeLa tumor cell lines, with IC50 values 9?±?2. The bindings of these complexes with Fish Sperm DNA were measured by electronic absorption spectra and fluorescence spectroscopy, showing K_sq 0.1867 (1), 0.1589 (2), 0.2332 (3), and 0.1411 (4), with the binding affinities ranked 3?>?1 > 2?>?4. The experimental result showed that these complexes could bind DNA via intercalation. The ability of 1–4 to cleave the pBR322 plasmid DNA was demonstrated by gel electrophoresis assay. The experiment verified that these complexes could induce DNA damage. In addition, flow cytometric analysis showed that 1–4 induced apoptosis of HeLa tumor cell lines; as time increases, the apoptotic impact becomes increasingly significant. The potential of 1–4 as anticancer agents were examined using molecular docking of the complexes with DNA.

     

A hydroxyquinoline-appended ruthenium(II)-polypyridyl complex that induces and stabilizes G-quadruplex DNA

A polypyridyl ruthenium(II) complex with hydroxyquinoline-derived ligand has been synthesized and characterized. The ability to act as telomeric quadruplex inducer and stabilizer, and quadruplex-binding properties of the complex have been evaluated by absorption and emission analyses, fluorescent intercalator displacement (FID) titrations, circular dichroism (CD) spectroscopy, polymerase chain reaction (PCR) stop assay, color reaction studies, fluorescence resonance energy transfer (FRET) melting assay, Job plot, and molecular modeling. Observations revealed that the complex could well induce and stabilize the formation of antiparallel G-quadruplex of telomeric DNA in the presence or absence of metal cations, and showed superior G-quadruplex selectivity over duplex DNA with remarkable ΔT_m value of 18.0?°C even at 50-fold excessive supplies of calf thymus (ct) DNA. The complex exhibited high interaction affinity of 2.56?×?10⁶ M^?1 with G-quadruplex DNA and evident luminescence enhancements of 3.1 and 4.2 times for quadruplex binding in Na⁺ and K⁺ buffer, respectively. In addition, the 1:1 [quadruplex]/[complex] binding mode ratio was determined. The results suggest that the complex can be developed as potential anticancer reagent through binding and stabilization of G-quadruplex DNA.