Publications by authors named "Christoph Janiak"

193 Publications

A Highly-Efficient Oxygen Evolution Electrocatalyst Derived from a Metal-Organic Framework and Ketjenblack Carbon Material.

Chempluschem 2021 Jul 1. Epub 2021 Jul 1.

Institut für Anorganische Chemie und Strukturchemie, Heinrich-, Heine-Universität Düsseldorf Universitätsstraße 1, 40225, Düsseldorf, Germany.

The composite of the metal-organic framework (MOF) Ni(Fe)-MOF-74 and the highly conductive carbon material ketjenblack (KB) could be easily obtained from the in-situ MOF synthesis in a one-step solvothermal reaction. The composite material features a remarkable electrochemical oxygen evolution reaction (OER) performance where the overpotential at 10 mA/cm and the current density at 1.7 V are recorded as 0.274 V and 650 mA/cm , respectively, in 1 mol/L KOH. In particular, the activation of nickel-iron clusters from the MOF under an applied anodic bias steadily boosts the OER performance. Although Ni(Fe)-MOF-74 goes through some structural modification during the electrochemical measurements, the stabilized and optimized composite material shows excellent OER performance. This simple strategy to design highly-efficient electrocatalysts, utilizing readily available precursors and carbon materials, will leverage the use of diverse metal-organic complexes into electrode fabrication with a high energy conversion efficiency.
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http://dx.doi.org/10.1002/cplu.202100278DOI Listing
July 2021

Covalent Triazine Frameworks Based on the First -Octahedral Hexanitrile Monomer via Nitrile Trimerization: Synthesis, Porosity, and CO Gas Sorption Properties.

Materials (Basel) 2021 Jun 10;14(12). Epub 2021 Jun 10.

Institute of Organic Chemistry (IOC), Karlsruhe Institute of Technology (KIT), Fritz-Haber-Weg 6, D-76131 Karlsruhe, Germany.

Herein, we report the first synthesis of covalent triazine-based frameworks (CTFs) based on a hexanitrile monomer, namely the novel pseudo-octahedral hexanitrile 1,4-bis(tris(4'-cyano-phenyl)methyl)benzene using both ionothermal reaction conditions with ZnCl at 400 °C and the milder reaction conditions with the strong Brønsted acid trifluoromethanesulfonic acid (TFMS) at room temperature. Additionally, the hexanitrile was combined with different di-, tri-, and tetranitriles as a second linker based on recent work of mixed-linker CTFs, which showed enhanced carbon dioxide captures. The obtained framework structures were characterized via infrared (IR) spectroscopy, elemental analysis, scanning electron microscopy (SEM), and gas sorption measurements. Nitrogen adsorption measurements were performed at 77 K to determine the Brunauer-Emmett-Teller (BET) surface areas range from 493 m/g to 1728 m/g (/ = 0.01-0.05). As expected, the framework synthesized from with ZnCl possesses the highest surface area for nitrogen adsorption. On the other hand, the mixed framework structure formed from the hexanitrile and 1,3,5 tricyanobenzene () shows the highest uptake of carbon dioxide and methane of 76.4 cm/g and 26.6 cm/g, respectively, at 273 K.
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http://dx.doi.org/10.3390/ma14123214DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8230500PMC
June 2021

A 2-(benzothiazol-2-yl)-phenolato platinum(II) complex as potential photosensitizer for combating bacterial infections in lung cancer chemotherapy†.

Eur J Med Chem 2021 Jun 10;222:113600. Epub 2021 Jun 10.

Departamento de Química Inorgánica, Universidad de Murcia and Institute for Bio-Health Research of Murcia (IMIB-Arrixaca), E-30071, Murcia, Spain. Electronic address:

Cancer and antibiotic resistance are two global health threats that usually hamper clinical chemotherapeutic efficacy. Particularly for lung cancer, bacterial infections frequently arise thereby complicating the course of cancer treatment. In this sense, three new neutral luminescent cycloplatinated(II) photosensitizers of the type [Pt(dmba)(L)] (dmba = N,N-dimethylbenzylamine-κN,κC; L = 2-(benzo[d]oxazol-2-yl)-phenolato-κN,κO1, 2-(benzo[d]thiazol-2-yl)-phenolato-κN,κO2, and 2-(1-methyl-1H-benzo[d]imidazole-2-yl)phenolato-κN,κO3) have been characterized and developed to potentially eliminate both resistant bacteria and lung cancer cells. The phototherapeutic effects of complex 2 have been evaluated using low doses of blue light irradiation. Complex 2 exerted promising photoactivity against pathogenic Gram-positive bacteria strains of clinical interest, displaying a phototoxic index (PI) of 15 for methicillin-resistant Staphylococcus aureus, one of the major microorganisms predominating lung infections. Likewise, the anticancer activity of 2 was also increased upon light irradiation in human lung A549 cancer cells (PI = 36). Further in vitro experiments with this platinum(II) complex suggest that ROS-generating photodynamic reactions were involved upon light irradiation, thus providing a reasonable mechanism for its dual anticancer and antibacterial activities.
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http://dx.doi.org/10.1016/j.ejmech.2021.113600DOI Listing
June 2021

Capture and Separation of SO Traces in Metal-Organic Frameworks via Pre-Synthetic Pore Environment Tailoring by Methyl Groups.

Angew Chem Int Ed Engl 2021 Jun 15. Epub 2021 Jun 15.

Hoffmann Institute of Advanced Materials, Shenzhen Polytechnic, 7098 Liuxian Blvd, Nanshan District, Shenzhen, 518055, China.

Herein, we report a pre-synthetic pore environment design strategy to achieve stable methyl-functionalized metal-organic frameworks (MOFs) for preferential SO binding and thus enhanced low (partial) pressure SO adsorption and SO /CO separation. The enhanced sorption performance is for the first time attributed to an optimal pore size by increasing methyl group densities at the benzenedicarboxylate linker in [Ni (BDC-X) DABCO] (BDC-X=mono-, di-, and tetramethyl-1,4-benzenedicarboxylate/terephthalate; DABCO=1,4-diazabicyclo[2,2,2]octane). Monte Carlo simulations and first-principles density functional theory (DFT) calculations demonstrate the key role of methyl groups within the pore surface on the preferential SO affinity over the parent MOF. The SO separation potential by methyl-functionalized MOFs has been validated by gas sorption isotherms, ideal adsorbed solution theory calculations, simulated and experimental breakthrough curves, and DFT calculations.
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http://dx.doi.org/10.1002/anie.202105229DOI Listing
June 2021

Pseudotetrahedral copper(II)-complexes with enantiopure ( or )-2-(((aryl)ethylimino)ethyl)phenolate Schiff base ligands.

Dalton Trans 2021 Jul;50(26):9236-9249

Institut für Anorganische Chemie und Strukturchemie, Heinrich-Heine-Universität, Universitätsstr. 1, D-40225 Düsseldorf, Germany.

Condensation of 2-hydroxy-benzophenone (HL') with (R or S)-(Ar)ethylamine yields the enantiopure Schiff bases (S or R)-2-((E)-1-(1-(Ar)ethylimino)ethyl)phenol {Ar = C6H5 (S- or R-HL1), p-CH3OC6H4 (S- or R-HL2)}. These Schiff bases react with copper(ii) acetate under reflux to give green microcrystals of bis[(R or S)-2-((E)-1-(1-(Ar)ethylimino)ethyl)phenolato-κ2N,O]-Λ/Δ-copper(ii), {Ar = C6H5 (Λ/Δ-Cu-R- or S-L1), p-CH3OC6H4 (Λ/Δ-Cu-R- or S-L2)} with induction of Λ/Δ-chirality at-metal. The presence of Schiff base ligands in the paramagnetic green microcrystals is confirmed by decomplexation reaction with NaCN via reduction of Cu(ii) to Cu(i) in DMSO-d6 solution. Crystallization attempts of the green microcrystalline Schiff-base Cu complexes provide deep-green block-shaped crystals of an about equal admixture of bis[2-oxo-benzophenonato-κ2O,O']-copper(ii), (CuL'2) and bis[2-(imino(phenyl)methyl)phenolato-κ2N,O]copper(ii), (CuL''2) via in situ hydrolysis of the coordinated Schiff base ligands back to 2-hydroxy-benzophenone (HL') and to 2-(imino(phenyl)methyl)phenol (HL''), which in-turn bind with the copper(ii) ion. Powder X-ray diffraction (PXRD) patterns of R-HL1 and Cu-R-L1 allowed their structure determinations using the program Expo-2014 followed by Rietveld refinement. The Cu structures refined to four-coordinated Λ/Δ-copper(ii)-complexes by the two phenolate-oxygen and two imine-nitrogen atoms from two Schiff base ligands in a pseudotetrahedral geometry. DFT optimized structures (at gas-phase) reveal the Δ-Cu-S-L1 or Λ-Cu-R-L1 diastereomer as slightly more stable than the corresponding Λ-Cu-S-L1 or Δ-Cu-R-L1 by ca. 7.60 kcal mol-1, resulting from diastereoselectively induced Λ vs. Δ-chirality at-metal. Electronic circular dichroism (ECD) spectra display mirror-image relationships and comparisons of experimental and simulated ECD spectra by TDDFT suggest an excess of the Δ-Cu-S-L1 or Λ-Cu-R-L1 diastereomer in solution. The cyclic voltammograms demonstrate two one electron charge transfer processes for Cu2+/Cu+ and Cu+/Cu0 couples in acetonitrile, respectively.
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http://dx.doi.org/10.1039/d1dt01671gDOI Listing
July 2021

Zirconium and Aluminum MOFs for Low-Pressure SO Adsorption and Potential Separation: Elucidating the Effect of Small Pores and NH Groups.

ACS Appl Mater Interfaces 2021 Jun 11;13(24):29137-29149. Epub 2021 Jun 11.

Institut für Anorganische Chemie und Strukturchemie, Heinrich-Heine-Universität Düsseldorf, Universitätsstraße 1, 40225 Düsseldorf, Germany.

Finding new adsorbents for the desulfurization of flue gases is a challenging task but is of current interest, as even low SO emissions impair the environment and health. Four Zr- and eight Al-MOFs (Zr-Fum, DUT-67(Zr), NU-1000, MOF-808, Al-Fum, MIL-53(Al), NH-MIL-53(Al), MIL-53(tdc)(Al), CAU-10-H, MIL-96(Al), MIL-100(Al), NH-MIL-101(Al)) were examined toward their SO sorption capability. Pore sizes in the range of about 4-8 Å are optimal for SO uptake in the low-pressure range (up to 0.1 bar). Pore widths that are only slightly larger than the kinetic diameter of 4.1 Å of the SO molecules allow for multi-side-dispersive interactions, which translate into high affinity at low pressure. Frameworks NH-MIL-53(Al) and NH-MIL-101(Al) with an NH-group at the linker tend to show enhanced SO affinity. Moreover, from single-gas adsorption isotherms, ideal adsorbed solution theory (IAST) selectivities toward binary SO/CO gas mixtures were determined with selectivity values between 35 and 53 at a molar fraction of 0.01 SO (10.000 ppm) and 1 bar for the frameworks Zr-Fum, MOF-808, NH-MIL-53(Al), and Al-Fum. Stability tests with exposure to dry SO during ≤10 h and humid SO during 5 h showed full retention of crystallinity and porosity for Zr-Fum and DUT-67(Zr). However, NU-1000, MOF-808, Al-Fum, MIL-53(tdc), CAU-10-H, and MIL-100(Al) exhibited ≥50-90% retained Brunauer-Emmett-Teller (BET)-surface area and pore volume; while NH-MIL-100(Al) and MIL-96(Al) demonstrated a major loss of porosity under dry SO and MIL-53(Al) and NH-MIL-53(Al) under humid SO. SO binding sites were revealed by density functional theory (DFT) simulation calculations with adsorption energies of -40 to -50 kJ·mol for Zr-Fum and Al-Fum and even above -50 kJ·mol for NH-MIL-53(Al), in agreement with the isosteric heat of adsorption near zero coverage (Δ). The predominant, highest binding energy noncovalent binding modes in both Zr-Fum and Al-Fum feature μ-OH···OSO hydrogen bonding interactions. The small pores of Al-Fum allow the interaction of two μ-OH bridges from opposite pore walls with the same SO molecule via OH···OSO···HO hydrogen bonds. For NH-MIL-53(Al), the DFT high-energy binding sites involve NH···OS together with the also present Al-μ-OH···OS hydrogen bonding interactions and C-π···SO, N···SO interactions.
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http://dx.doi.org/10.1021/acsami.1c06003DOI Listing
June 2021

Cucurbituril-Encapsulating Metal-Organic Framework via Mechanochemistry: Adsorbents with Enhanced Performance.

Angew Chem Int Ed Engl 2021 Jul 9;60(28):15365-15370. Epub 2021 Jun 9.

Hoffmann Institute of Advanced Materials, Shenzhen Polytechnic, 7098 Liuxian Blvd, Nanshan District, Shenzhen, 518055, China.

The first examples of monolithic crystalline host-guest hybrid materials are described. The reaction of 1,3,5-benzenetricarboxylic acid (H BTC) and Fe(NO ) ⋅9 H O in the presence of decamethylcucurbit[5]uril ammonium chloride (MC5⋅2 NH Cl⋅4 H O) directly affords [email protected](Fe) hybrid monoliths featuring hierarchical micro-, meso- and macropores. Particularly, this "bottle-around-ship" synthesis and one-pot shaping are facilitated by a newly discovered Fe-MC5 flowing gel formed by mechanochemistry. The designed [email protected](Fe) hybrid material with MC5 as active domains shows enhanced CH and lead(II) uptake performance, and selective capture of lead(II) cations at low concentrations. This shows that host-guest hybrid materials can exhibit synergic properties that out-perform materials based on individual components.
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http://dx.doi.org/10.1002/anie.202100675DOI Listing
July 2021

Nickel nanoparticle-decorated reduced graphene oxide/WO nanocomposite - a promising candidate for gas sensing.

Beilstein J Nanotechnol 2021 15;12:343-353. Epub 2021 Apr 15.

Institut für Anorganische Chemie und Strukturchemie, Heinrich-Heine-Universität Düsseldorf, 40204 Düsseldorf, Germany.

We report for the first time the combination of WO sensing elements with a non-noble metal-carbon composite, namely a nickel metal nanoparticle-carbon composite ([email protected]). Previous work with WO had used either NiO (as part of the WO lattice), solely carbon, Pd-surface decorated WO ([email protected]), or Pd or [email protected]@WO. We demonstrate the gas response for pure WO, rGO/WO and [email protected]/WO sensing elements towards NO and acetone in air as well as towards CO in N. The addition of 0.35 wt % [email protected]O composite to WO enables the increase of the sensory response by more than 1.6 times for NO vapors. The gas response towards acetone using 0.35 wt % [email protected]/WO composite was 1.5 times greater for 3500 ppm than for 35,000 ppm acetone. For 0.35 wt % [email protected]/WO composite and CO gas, a response time ( ) of 7 min and a recovery time ( ) of 2 min was determined.
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http://dx.doi.org/10.3762/bjnano.12.28DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8056068PMC
April 2021

Fluorescent Indolo[3,2-a]phenazines against Toxoplasma gondii: Concise Synthesis by Gold-Catalyzed Cycloisomerization with 1,2-Silyl Migration and ipso-Iodination Suzuki Sequence.

Chemistry 2021 Jul 27;27(38):9774-9781. Epub 2021 May 27.

Institut für Organische Chemie und Makromolekulare Chemie, Heinrich-Heine-Universität Düsseldorf, Universitätsstraße 1, 40225, Düsseldorf, Germany.

A gold-catalyzed cycloisomerization of 2-indolyl-3-[(trimethylsilyl)ethynyl)]quinoxalines with concomitant 1,2-silyl shift forms 6-(trimethylsilyl)indolo[3,2-a]phenazines in moderate to excellent yield. These silylated heterocycles are readily transformed into 6-aryl-indolo[3,2-a]phenazines in moderate to good yield by one-pot ipso-iodination Suzuki coupling. The title compounds represent a novel type of tunable luminophore. Structure-property relationships for 6-aryl-indolo[3,2-a]phenazines obtained from Hammett correlations with σ substituent parameters indicate that emission maxima, Stokes shifts, and fluorescence quantum yields can be fine-tuned by the remote para-aryl substituent. Furthermore, indolo[3,2-a]phenazines were found to exhibit interesting activities against medically relevant pathogens such as the Apicomplexa parasite Toxoplasma gondii with an IC of up to 0.67±0.13 μM. Thus, these compounds are promising candidates for novel anti-parasitic therapies.
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http://dx.doi.org/10.1002/chem.202101391DOI Listing
July 2021

Ultimate Corrosion to Pt-Cu Electrocatalysts for Enhancing Methanol Oxidation Activity and Stability in Acidic Media.

Chemistry 2021 Jun 19;27(35):9124-9128. Epub 2021 May 19.

State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, School of Materials Science & Engineering, International School of Materials Science & Engineering, School of Chemistry, Chemical Engineering and Life Science, Wuhan University of Technology, Wuhan, 430070, P. R. China.

Alloying platinum (Pt) with transition metals (M), as an established class of electrocatalysts, reduces the use of Pt and improves the electrocatalytic performance. However, the stability of transition metals in nanostructured platinum alloys is a fundamental and practical problem in electrocatalysis, due to leaching of transition metals under acidic operating condition. Here, a corrosion method has been developed for a Pt-Cu electrocatalyst with high activity (6.6 times that of commercial Pt/C) and excellent stability for the methanol oxidation reaction (MOR) under acidic operating conditions. The mechanism of formation has been studied, and possible mesostructured re-formation and atomic re-organization have been proposed. This work offers an effective strategy for the facile synthesis of a highly acid-stable PtM alloying and opens a door to high-performance design for electrocatalysts.
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http://dx.doi.org/10.1002/chem.202100754DOI Listing
June 2021

Augmented Therapeutic Potential of Glutaminase Inhibitor CB839 in Glioblastoma Stem Cells Using Gold Nanoparticle Delivery.

Pharmaceutics 2021 Feb 23;13(2). Epub 2021 Feb 23.

Institut für Anorganische Chemie und Strukturchemie, Heinrich-Heine-Universität Düsseldorf, 40204 Düsseldorf, Germany.

Gold nanoparticles (Au NPs) are studied as delivery systems to enhance the effect of the glutaminase1 inhibitor CB839, a promising drug candidate already in clinical trials for tumor treatments. Au NPs were synthesized using a bottom-up approach and covered with polymers able to bind CB839 as a Au-polymer-CB839 conjugate. The drug loading efficiency (DLE) was determined using high-performance liquid chromatography and characterization of the CB839-loaded NPs was done with various microscopic and spectroscopic methods. Despite the chemical inertness of CB839, Au NPs were efficient carriers with a DLE of up to 12%, depending on the polymer used. The therapeutic effect of CB839 with and without Au was assessed in vitro in 2D and 3D glioblastoma (GBM) cell models using different assays based on the colony formation ability of GBM stem cells (GSCs). To avoid readout disturbances from the Au metal, viability methods which do not require optical detection were hereby optimized. These showed that Au NP delivery increased the efficacy of CB839 in GSCs, compared to CB839 alone. Fluorescent microscopy proved successful NP penetration into the GSCs. With this first attempt to combine CB839 with Au nanotechnology, we hope to overcome delivery hurdles of this pharmacotherapy and increase bioavailability in target sites.
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http://dx.doi.org/10.3390/pharmaceutics13020295DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7926460PMC
February 2021

Organoplatinum(II) Complexes Self-Assemble and Recognize AT-Rich Duplex DNA Sequences.

Inorg Chem 2021 Feb 27;60(4):2178-2187. Epub 2021 Jan 27.

Departamento de Química Inorgánica, Universidad de Murcia, and Biomedical Research Institute of Murcia (IMIB-Arrixaca), E-30071 Murcia, Spain.

The specific recognition of AT-rich DNA sequences opens up the door to promising diagnostic and/or therapeutic strategies against gene-related diseases. Here, we demonstrate that amphiphilic Pt complexes of the type [Pt(dmba)(N∧N)]NO (dmba = ,-dimethylbenzylamine-κ κ; N∧N = dpq (), dppz (), and dppn ()) recognize AT-rich oligonucleotides over other types of DNA, RNA, and model proteins. The crystal structure of shows the presence of significant π-stacking interactions and a distorted coordination sphere of the d Pt atom. Complex , containing the largest π-conjugated ligand, forms supramolecular assemblies at high concentrations under aqueous environment. However, its aggregation can be promoted in the presence of DNA at concentrations as low as 10 μM in a process that "turns on" its excimer emission around 600 nm. Viscometry, gel electrophoresis, and theoretical calculations demonstrate that binds to minor groove when self-assembled, while the monomers of and intercalate into the DNA. The complexes also inhibit cancer cell growth with low-micromolar IC values in 2D tissue culture and suppress tumor growth in 3D tumor spheroids with a multicellular resistance (MCR) index comparable to that of cisplatin.
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http://dx.doi.org/10.1021/acs.inorgchem.0c02648DOI Listing
February 2021

PtPd hollow nanocubes with enhanced alloy effect and active facets for efficient methanol oxidation reaction.

Chem Commun (Camb) 2021 Jan 13;57(8):986-989. Epub 2021 Jan 13.

State Key Laboratory of Advanced Technology for Materials Synthesis and Processing & School of Materials Science and Engineering, Wuhan University of Technology, 122 Luoshi Road, Wuhan, 430070, China.

We report an alternating-reduction approach by galvanic replacement and co-reduction to enable incorporation of Pd into Pt shell, and the obtained PtPd hollow nanocubes with an enhanced alloy effect and highly active {100} facets show high catalytic activity and superior durability in the methanol oxidation reaction.
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http://dx.doi.org/10.1039/d0cc06876dDOI Listing
January 2021

Dual ionic liquid-based crosslinked chitosan for fine-tuning of antifouling, water throughput, and denitrification performance of polysulfone membrane.

Int J Biol Macromol 2021 Feb 29;170:572-582. Epub 2020 Dec 29.

Institut für Anorganische Chemie und Strukturchemie, Heinrich-Heine Universität Düsseldorf, 40204 Düsseldorf, Germany.

This study aimed to design a facile and efficient protocol for upgrading the performance indices of polysulfone (PS) membrane (porosity, hydrophilicity, pure water flux (PWF), surface charge, and fouling-resistance) by blending with newly synthesized poly(ionic) crosslinked chitosan Schiff bases (PICCSBs). The PS-PICCSBs mixed-matrix membranes (MMMs) have successfully fabricated and characterized based on spectral and microscopic analyses, porosity, zeta potential, water contact angle, and water uptake (wettability) measurements. The PWF, fouling-resistance against bovine serum albumin (BSA), as well as ion exchange capacity (IEC) against nitrate anion were studied. The wettability, hydrophilicity and overall porosity of new MMMs have greatly increased, in comparison to a pristine PS membrane (M). In addition, blending of PS with PICCSBs resulted in switching its surface from negatively- to positively-charged. The PWF of MMMs has increased to reach a maximum value of 238.6 L/m h for MMM (9.3-fold higher than M). Meanwhile, BSA rejection has declined from 96.62% for M to 41.9% for MMM. The fouling parameters results of MMMs indicated their low fouling propensity. The IEC of nitrate anions revealed that the nitrate uptake by MMM is higher than that for M and MMM by 34% and 14%, respectively.
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http://dx.doi.org/10.1016/j.ijbiomac.2020.12.186DOI Listing
February 2021

Tetrahydrothiophene-Based Ionic Liquids: Synthesis and Thermodynamic Characterizations.

ChemistryOpen 2021 Feb 23;10(2):153-163. Epub 2020 Dec 23.

Institut für Anorganische Chemie und Strukturchemie, Heinrich-Heine-Universität Düsseldorf, 40204, Düsseldorf, Germany.

S-alkyltetrahydrothiophenium, [C THT] bis(trifluorosulfonyl)imide, [NTf ] room temperature ionic liquids (ILs) and tetraphenylborate, [BPh ] salts with alkyl chain lengths from C to C have been prepared. The ILs and salts were characterized and their purity verified by H- and C-nuclear magnetic resonance, elemental analysis, ion chromatography, Karl-Fischer titration, single crystal X-ray diffraction as well as thermogravimetric analysis. The experimentally determined density and viscosity decrease with increasing temperature. The experimental solubility of the [C THT][NTf ]-ILs in water (75 to 2.2 mg/L for C to C ) was modelled with very good agreement by Perturbed Chain Statistical Associating Fluid Theory (PC-SAFT), based on the extremely low vapor pressures for the [C THT][NTf ]-ILs measured in this work (4.15 to 0.037 ⋅ 10 ×p for C to C ). PC-SAFT is able to predict and correlate different thermodynamic properties by estimating the Helmholtz residual energy.
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http://dx.doi.org/10.1002/open.202000228DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7874261PMC
February 2021

Isocyanide-based consecutive Bargellini/Ugi reactions: an efficient method for the synthesis of pseudo-peptides containing three amide bonds.

Amino Acids 2021 Jan 27;53(1):1-10. Epub 2020 Nov 27.

Institut Für Anorganische Chemie und Strukturchemie, Heinrich-Heine-Universität Düsseldorf, 40204, Düsseldorf, Germany.

Isocyanide-based consecutive Bargellini/Ugi multicomponent reactions as a combinatorial strategy have been developed for the synthesis of new class of pseudo-peptides. Via Bargellini reaction 3-carboxamido-isobutyric acids are prepared using acetone, chloroform, sodium hydroxide, and isocyanides. Then, using Ugi multicomponent reaction strategy, pseudo-peptides containing three amide bonds are synthesized using the Bargellini reaction product, aldehydes, amines, and isocyanides. This is an efficient and eco-friendly approach for easy access to wide variety of structurally diverse, drug-like pseudo-peptides from cheap and readily available precursors in high yields.
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http://dx.doi.org/10.1007/s00726-020-02917-1DOI Listing
January 2021

Introducing Bluish-Green Light-Emitting Diodes (OLEDs) and Tuning Their Color Intensity by Uranium Complexes: Synthesis, Characterization, and Photoluminescence Studies of 8-Hydroxyquinoline Complexes of Uranium.

Inorg Chem 2020 Dec 24;59(23):17028-17037. Epub 2020 Nov 24.

Institut für Anorganische Chemie und Strukturchemie Heinrich-Heine Universität, D-40204 Düsseldorf, Germany.

To improve our understanding of the chemistry of actinide complexes and to spur their development in the field of actinide markers, two new uranium complexes were synthesized using 8-hydroxyquinoline and 5,7-dichloro-8-hydroxyquinoline. The prepared complexes were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, ultraviolet-visible spectroscopy, elemental analysis, and single-crystal X-ray diffraction. The impact of the electron-withdrawing group of the ligand on the photoluminescence spectra of the complexes in solution and in the solid state was scrutinized. The bandgap of the complexes was calculated using the density functional theory (DFT) method to investigate the effects of the electron-withdrawing groups on energy levels. The synthesized uranium complexes demonstrated appropriate levels of the lowest unoccupied molecular orbital energy, leading to favorable dye stability. The prepared uranium complexes showed blue fluorescent emission, and the sample with the most intense fluorescence was used to construct bluish-green organic light-emitting diodes using simple solution processing fabrication methods. Absorbance spectra, emission spectra, DFT-calculated energy levels, and comparisons of the fabricated organic light-emitting diodes indicated that the electron-withdrawing group was a key factor in photoluminescence behavior.
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http://dx.doi.org/10.1021/acs.inorgchem.0c02242DOI Listing
December 2020

Synthesis of Substituted Phthalimides Ultrasound-Promoted One-Pot Multicomponent Reaction.

J Org Chem 2021 01 23;86(1):574-580. Epub 2020 Nov 23.

Institut für Anorganische Chemie, und Strukturchemie Heinrich-Heine-Universität Düsseldorf, I40225 Düsseldorf, Germany.

In this work, a novel strategy for the straightforward synthesis of substituted phthalimides is described, which includes base-mediated Michael addition/intramolecular cyclization/[1,5]- shift/cleavage of CS/aromatization/nucleophilic acyl substitution reaction of 2-(4-oxo-2-thioxothiazolidin-5-ylidene)acetates and ,-dicyanoolefines under ultrasound (US) irradiation. Some advantages of this method are as follows: having simple operation, easily accessible starting materials, chemoselective cascade process, synthetically useful yields, and green conditions by utilizing US irradiation as a source of energy and using ethanol as solvent.
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http://dx.doi.org/10.1021/acs.joc.0c02245DOI Listing
January 2021

Enzymatic Activity of CD73 Modulates Invasion of Gliomas via Epithelial-Mesenchymal Transition-Like Reprogramming.

Pharmaceuticals (Basel) 2020 Nov 11;13(11). Epub 2020 Nov 11.

Department of Neurosurgery, University Hospital Bonn, 53179 Bonn, Germany.

Glioblastoma (GBM) is the most aggressive malignant primary brain tumour in adulthood. Despite strong research efforts current treatment options have a limited impact on glioma stem-like cells (GSCs) which contribute to GBM formation, progression and chemoresistance. Invasive growth of GSCs is in part associated with epithelial-mesenchymal-like transition (EMT), a mechanism associated with CD73 in several cancers. Here, we show that CD73 regulates the EMT activator SNAIL1 and further investigate the role of enzymatic and non-enzymatic CD73 activity in GBM progression. Reduction of CD73 protein resulted in significant suppression of GSC viability, proliferation and clonogenicity, whereas CD73 enzymatic activity exhibited negative effects only on GSC invasion involving impaired downstream adenosine (ADO) signalling. Furthermore, application of phosphodiesterase inhibitor pentoxifylline, a potent immunomodulator, effectively inhibited ZEB1 and CD73 expression and significantly decreased viability, clonogenicity, and invasion of GSC in vitro cultures. Given the involvement of adenosine and A adenosine receptor in GSC invasion, we investigated the effect of the pharmacological inhibition of AAR on GSC maintenance. Direct AAR inhibition promoted apoptotic cell death and impaired the clonogenicity of GSC cultures. Taken together, our data indicate that CD73 is an exciting novel target in GBM therapy. Moreover, pharmacological interference, resulting in disturbed ADO signalling, provides new opportunities to innovate GBM therapy.
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http://dx.doi.org/10.3390/ph13110378DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7698190PMC
November 2020

Design and properties of multiple-emitter luminescent metal-organic frameworks.

Chem Commun (Camb) 2020 Oct 24;56(82):12290-12306. Epub 2020 Sep 24.

Hoffmann Institute of Advanced Materials, Shenzhen Polytechnic, 7098 Liuxian Blvd, Nanshan, Shenzhen, China.

Multi-emitter luminescent metal-organic frameworks (LMOFs) possess multiple emission bands that can cover a wider spectral region, which is a prerequisite for white-light emitting and multi-dimensional ratiometric fluorescent sensing. By taking advantage of the structure features of MOFs (e.g. hybrid structure, porosity) and the various luminescence origins of LMOFs, different emission sources can be designed and combined with each other into a homogeneous solid-state LMOF phase with the desired emission properties. This feature article reviews the recent development of multi-emitter LMOFs, and focuses on the design strategies for creating multi-emitter LMOFs based on at least two emission centers. The design strategies are classified into and discussed along six categories: type I metal-linker emitters, Type II multi-metal emitters, Type III multi-linker emitters, Type IV [email protected] (chromophore incorporated into an already luminescent MOF), Type V [email protected] (multi-chromophores embedded into a non-emissive MOF) and Type VI multi-heterostructure LMOF emitters. The new class of Type VI includes core-shell structured LMOF⊃LMOF and nanostructured LMOF/LMOF thin films on a substrate. The good spatial separation between the different emitters in their own but chemically linked LMOF phase can retain their emission properties with less interference with the other emitters.
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http://dx.doi.org/10.1039/d0cc04733cDOI Listing
October 2020

Increase of network hydrophilicity from sql to lvt supramolecular isomers of Cu-MOFs with the bifunctional 4-(3,5-dimethyl-1-pyrazol-4-yl)benzoate linker.

Dalton Trans 2020 Sep;49(36):12854-12864

Institut für Anorganische Chemie und Strukturchemie, Heinrich-Heine Universität Düsseldorf, 40204 Düsseldorf, Germany.

The bifunctional linker 4-(3,5-dimethyl-1H-pyrazol-4-yl)benzoic acid (H2mpba) was used for the synthesis of new (square lattice) sql 2D metal-organic frameworks (MOFs) [Cu(Hmpba)2]·L (L = DMF or ACN) in a solvent-mixture of dimethylformamide/water and acetonitrile/water. These sql 2D MOFs are supramolecular isomers of the lvt 3D network [Cu(Hmpba)2]·4MeOH·1H2O (lvt-MeOH) that was synthesized previously by Richardson and co-workers. All these frameworks are potentially porous structures with solvent molecules included in the channels of the as synthesized materials. After activation all three materials showed good CO2 adsorption capacity, demonstrated here for lvt-MeOH for the first time, with a saturation uptake of 113 cm3 g-1 (lvt-MeOH-act.), 111 cm3 g-1 (sql-DMF-act.) and 90 cm3 g-1 (sql-ACN-act.) at 195 K. The flexibility of the lvt-MeOH-act. network is evidenced by a gate-opening effect seen in the CO2 measurement at 195 K and under gravimetric high-pressure CO2 adsorption. According to the water and ethanol sorption measurements the new sql frameworks can be categorized as hydrophobic materials in contrast to the hydrophilic lvt framework. In the lvt-MeOH structure the crystal solvent can be replaced with water to yield the structurally authenticated water-only network lvt-H2O containing 3D arrays of S4-symmetric (H2O)20 clusters.
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http://dx.doi.org/10.1039/d0dt02642eDOI Listing
September 2020

A practical guide to calculate the isosteric heat/enthalpy of adsorption via adsorption isotherms in metal-organic frameworks, MOFs.

Dalton Trans 2020 Aug;49(30):10295-10307

Institut für Anorganische Chemie und Strukturchemie, Heinrich-Heine-Universität Düsseldorf, D-40204 Düsseldorf, Germany.

Porous materials such as MOFs are interesting candidates for gas separation and storage. An important parameter to gain deeper insights to the adsorption process of an adsorptive on an adsorbent is the isosteric enthalpy of adsorption, ΔHads which is defined as the heat to be released/required when an adsorptive binds to/detaches from the solid surface of an adsorbent. Two or three adsorption isotherms at different but close temperatures with ΔT ≤ 20 K for two and ΔT ≈ 10 K for three isotherms are the basis to derive the isosteric enthalpy of adsorption through the Clausius-Clapeyron approach or the virial analysis. This Perspective presents the procedure of the common (dual-site) Freundlich-Langmuir fit/Clausius-Clapeyron approach and the virial fit of the isotherms with usable Excel sheets and Origin files for the subsequent derivation of ΔHads. Exemplary adsorption isotherms of CO2, SO2 and H2 at two temperatures on MOFs are analyzed. The detailed computational description and comparison of the Clausius-Clapeyron approach and the virial analysis to determine ΔHads outlines the limitations of the two methods with respect to the available experimental data, especially at low pressure/low uptake values. It is emphasized that no extrapolation beyond the experimental data range should be done. The quality of the important and underlying isotherm fits must be checked and ensured with logarithmic-scale n/p isotherm plots for the (dual-site) Freundlich-Langmuir fit in the low-pressure region and through low standard deviations for the coefficients in the virial analysis.
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http://dx.doi.org/10.1039/d0dt01784aDOI Listing
August 2020

New Microporous Lanthanide Organic Frameworks. Synthesis, Structure, Luminescence, Sorption, and Catalytic Acylation of 2-Naphthol.

Molecules 2020 Jul 3;25(13). Epub 2020 Jul 3.

Institut für Anorganische Chemie und Strukturchemie, Heinrich-Heine Universität Düsseldorf, Universitätsstr. 1, D 40225 Düsseldorf, Germany.

New metal-organic frameworks (MOF) with lanthanum(III), cerium(III), neodymium(III), europium(III), gadolinium(III), dysprosium(III), and holmium(III)] and the ligand precursor tris(-carboxyphenyl)--trimethylbenzene (HL) were synthesized under solvothermal conditions. Single crystal x-ray analysis confirmed the formation of three-dimensional frameworks of [LnL(HO)]·xDMF·yHO for Ln = La, Ce, and Nd. From the nitrogen sorption experiments, the compounds showed permanent porosity with Brunauer-Emmett-Teller (BET) surface areas of about 400 m/g, and thermal stability up to 500 °C. Further investigations showed that these Ln-MOFs exhibit catalytic activity, paving the way for potential applications within the field of catalysis.
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http://dx.doi.org/10.3390/molecules25133055DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7411860PMC
July 2020

Solid-state to solution helicity inversion of pseudotetrahedral chiral copper(ii) complexes with 2,4-dihalo-salicylaldiminate ligands.

Dalton Trans 2020 Jun;49(24):8247-8264

Department of Chemistry, University of Isfahan, Isfahan 81746-73441, Iran.

The enantiopure Schiff bases (R or S)-N-1-(phenyl)ethyl-2,4-X1,X2-salicylaldimine (X1, X2 = Cl, Br, I) coordinate to copper(ii) and provide pseudotetrahedral bis[(S or R)-N-1-(phenyl)ethyl-(2,4-X1,X2-salicylaldiminato-κ2N,O)]-Δ/Λ-Cu(ii) (Λ/Δ-Cu-R or Δ/Λ-Cu-S). An induced Λ and Δ-chirality at-metal centre has been launched along the C2-axis of the molecule. Steric constraints brought by halogen substituents on the coordinating salicylal ring provide diastereoselectively Λ-Cu-R or Δ-Cu-S as major and Δ-Cu-R or Λ-Cu-S as minor diastereomers at solid-state, as evidenced by X-ray crystal structures and PXRD analyses. These results reveal inversion of induced chirality at-metal in comparison to the similar complexes without halogen substituents on the salicylal ring. Electronic circular dichroism (ECD) spectra show mirror-image relationships, confirming enantiomeric excess of the R or S-ligated complexes in solution. Comparisons of experimental and simulated ECD spectra suggest diastereomeric excess of Δ-Cu-R or Λ-Cu-S in solution which correspond to an inversion from the found solid-state Λ-Cu-R or Δ-Cu-S as major diastereomers. In addition, the optimized gas-phase structures also reveal Δ-Cu-R or Λ-Cu-S as slightly more stable than Λ-Cu-R or Δ-Cu-S. Thus, solid-state versus solution (or gas-phase) studies also indicate an interconversion of induced chirality (helicity inversion) at-metal from Λ-Cu-R or Δ-Cu-S to Δ-Cu-R or Λ-Cu-S. Thermal stability increases with the molecular weight of the complexes following Cl < ClBr < Br < I substituents. Hirshfeld surface analyses explore the strongest halogen (ortho)-halogen (para) interactions between two molecules in Λ-Cu-R3 or Δ-Cu-S3 at a distance shorter than the sum of the van der Waals radii of the two iodine atoms, provide a brilliant red spot on the dnorm surfaces. EPR spectra along with simulation suggest an axial symmetry with gz > gx,y > 2.0 and values for gz/Az ≥ 135 cm indicate pseudotetrahedral geometry for the complexes.
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http://dx.doi.org/10.1039/d0dt01649gDOI Listing
June 2020

Nickel nanoparticles supported on a covalent triazine framework as electrocatalyst for oxygen evolution reaction and oxygen reduction reactions.

Beilstein J Nanotechnol 2020 11;11:770-781. Epub 2020 May 11.

Institut für Anorganische Chemie und Strukturchemie, Heinrich-Heine-Universität Düsseldorf, 40204 Düsseldorf, Germany.

Covalent triazine frameworks (CTFs) are little investigated, albeit they are promising candidates for electrocatalysis, especially for the oxygen evolution reaction (OER). In this work, nickel nanoparticles (from Ni(COD)) were supported on CTF-1 materials, which were synthesized from 1,4-dicyanobenzene at 400 °C and 600 °C by the ionothermal method. CTF-1-600 and Ni/CTF-1-600 show high catalytic activity towards OER and a clear activity for the electrochemical oxygen reduction reaction (ORR). Ni/CTF-1-600 requires 374 mV overpotential in OER to reach 10 mA/cm, which outperforms the benchmark RuO catalyst, which requires 403 mV under the same conditions. Ni/CTF-1-600 displays an OER catalytic activity comparable with many nickel-based electrocatalysts and is a potential candidate for OER. The same Ni/CTF-1-600 material shows a half-wave potential of 0.775 V for ORR, which is slightly lower than that of commercial Pt/C (0.890 V). Additionally, after accelerated durability tests of 2000 cycles, the material showed only a slight decrease in activity towards both OER and ORR, demonstrating its superior stability.
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http://dx.doi.org/10.3762/bjnano.11.62DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7237812PMC
May 2020

Probing the limits of linker substitution in aluminum MOFs through water vapor sorption studies: mixed-MOFs instead of mixed-linker CAU-23 and MIL-160 materials.

Dalton Trans 2020 Jun;49(22):7373-7383

Institut für Anorganische Chemie und Strukturchemie, Heinrich-Heine-Universität, D-40204 Düsseldorf, Germany.

We report a systematic study on the possibility of forming mixed-linker metal-organic frameworks (MOFs) spanning between the aluminum MOFs CAU-23 and MIL-160 with their 2,5-thiophenedicarboxylate (TDC) and 2,5-furandicarboxylate (FDC) linkers, respectively. The planned synthesis of a mixed-linker MOF, combining TDC and FDC in the framework turned out to yield a rather largely intricate mixture of CAU-23 and MIL-160. This is due to the different opening angles of 150° for TDC versus 120° for FDC and the concomitant cis-trans versus cis-only OH-bridges in the infinite secondary building unit {Al(μ-OH)(O2C-)} chains. At the same time, the CAU-23 phase is accompanied by the polymorphic MIL-53-TDC phase with trans-only OH-bridges. The measurement of water vapor sorption isotherms was the method of choice to confirm the formation of mixed MOFs instead of mixed-linker phases. Thereby, the water sorption isotherms indicate the simultaneous formation of both MOF phases, albeit they do not exclude mixed-linker MOFs which may have formed at low levels of substitution. The differentiation via powder X-ray diffractometry (PXRD), IR-spectroscopy and nitrogen sorption was either not conclusive enough or impossible, due to similarities of the neat MOF phases. The synthesized MOF mixtures within the TDC : FDC ratios of 38 : 62 up to 82 : 18 exhibit two or three uptake steps in the water sorption isotherm, with the first two corresponding to an overlay from the individual water sorption isotherm of CAU-23 and MIL-160 and a third one from the additional MIL-53-TDC.
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http://dx.doi.org/10.1039/d0dt01044hDOI Listing
June 2020

Encapsulation of Phosphorescent Pt(II) Complexes in Zn-Based Metal-Organic Frameworks toward Oxygen-Sensing Porous Materials.

Inorg Chem 2020 May 7;59(10):7252-7264. Epub 2020 May 7.

CiMIC, SoN, Institut für Anorganische und Analytische Chemie, Westfälische Wilhelms-Universität Münster, Corrensstraße 28/30, 48149 Münster, Germany.

In this work, we synthesized two tailored phosphorescent Pt(II) complexes bearing a cyclometalating tridentate thiazole-based C^N*N pincer luminophore () and exchangeable chlorido () or cyanido () coligands. While both complexes showed photoluminescence from metal-perturbed ligand-centered triplet states (MP-LC), reached the highest phosphorescence quantum yields and displayed a significant sensitivity toward quenching by O. We encapsulated them into two Zn-based metal-organic frameworks, namely, and . The incorporation of the organometallic compounds in the resulting composites , , , and was verified by powder X-ray diffractometry, scanning electron microscopy, time-resolved photoluminescence spectroscopy and microscopy, as well as N- and Ar-gas sorption studies. The amount of encapsulated complex was determined by graphite furnace atomic absorption spectroscopy, showing a maximum loading of 3.7 wt %. If compared with their solid state forms, the solid-solution composites showed prolonged O-sensitive excited state lifetimes for the complexes at room temperature, reaching up to 18.4 μs under an Ar atmosphere, which is comparable with the behavior of the complex in liquid solutions or even frozen glassy matrices at 77 K.
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http://dx.doi.org/10.1021/acs.inorgchem.0c00678DOI Listing
May 2020

Spatial Heterojunction in Nanostructured TiO and Its Cascade Effect for Efficient Photocatalysis.

Nano Lett 2020 May 4;20(5):3122-3129. Epub 2020 May 4.

State Key Laboratory of Advanced Technology for Materials Synthesis and Processing & School of materials science and engineering & School of Chemistry, Chemical Engineering and Life Science, Wuhan University of Technology, Wuhan 430070, China.

A highly efficient photoenergy conversion is strongly dependent on the cumulative cascade efficiency of the photogenerated carriers. Spatial heterojunctions are critical to directed charge transfer and, thus, attractive but still a challenge. Here, a spatially ternary titanium-defected [email protected] quantum [email protected] graphene oxide (denoted as @[email protected]) in one system is shown to demonstrate a cascade effect of charges and significant performances regarding the photocurrent, the apparent quantum yield, and photocatalysis such as H production from water splitting and CO reduction. A key aspect in the construction is the technologically irrational junction of Ti-vacancies and nanocarbons for the spatially inside-out heterojunction. The new "spatial heterojunctions" concept, characteristics, mechanism, and extension are proposed at an atomic-/nanoscale to clarify the generation of rational heterojunctions as well as the cascade electron transfer.
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http://dx.doi.org/10.1021/acs.nanolett.9b05121DOI Listing
May 2020

Azaphilones from the Red Sea Fungus .

Mar Drugs 2020 Apr 10;18(4). Epub 2020 Apr 10.

Institute of Pharmaceutical Biology and Biotechnology, Heinrich-Heine-University Duesseldorf, 40225 Duesseldorf, Germany.

The marine-derived fungus , isolated from sediment collected from the Canyon at Dahab, Red Sea, yielded two new chlorinated azaphilones, falconensins O and P ( and ) in addition to four known azaphilone derivatives (-) following fermentation of the fungus on solid rice medium containing 3.5% NaCl. Replacing NaCl with 3.5% NaBr induced accumulation of three additional new azaphilones, falconensins Q-S (-) including two brominated derivatives ( and ) together with three known analogues (-). The structures of the new compounds were elucidated by 1D and 2D NMR spectroscopy and HRESIMS data as well as by comparison with the literature. The absolute configuration of the azaphilone derivatives was established based on single-crystal X-ray diffraction analysis of , comparison of NMR data and optical rotations as well as on biogenetic considerations. Compounds , -, and showed NF-κB inhibitory activity against the triple negative breast cancer cell line MDA-MB-231 with IC values ranging from 11.9 to 72.0 µM.
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http://dx.doi.org/10.3390/md18040204DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7231052PMC
April 2020

Interfacial co-existence of oxygen and titanium vacancies in nanostructured TiO for enhancement of carrier transport.

Nanoscale 2020 Apr 2;12(15):8364-8370. Epub 2020 Apr 2.

State Key Laboratory of Advanced Technology for Materials Synthesis and Processing & School of materials science and engineering, Wuhan University of Technology, Wuhan, 430070, China.

The interfacial co-existence of oxygen and metal vacancies in metal oxide semiconductors and their highly efficient carrier transport have rarely been reported. This work reports on the co-existence of oxygen and titanium vacancies at the interface between TiO and rGO via a simple two-step calcination treatment. Experimental measurements show that the oxygen and titanium vacancies are formed under 550 °C/Ar and 350 °C/air calcination conditions, respectively. These oxygen and titanium vacancies significantly enhance the transport of interfacial carriers, and thus greatly improve the photocurrent performances, the apparent quantum yield, and photocatalysis such as photocatalytic H production from water-splitting, photocatalytic CO reduction and photo-electrochemical anticorrosion of metals. A new "interfacial co-existence of oxygen and titanium vacancies" phenomenon, and its characteristics and mechanism are proposed at the atomic-/nanoscale to clarify the generation of oxygen and titanium vacancies as well as the interfacial carrier transport.
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http://dx.doi.org/10.1039/d0nr01180kDOI Listing
April 2020
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