Heterometallic bridged Pt(II)‐Zn(II) complexes: Influence of the substituent in 4′‐position in inert terpy ligand on antigenotoxicity, potential antitumor activity and mechanism of interactions of the complexes with biomolecules

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Heterometallic bridged Pt(II)-Zn(II) complexes: Influence of the substituent in 4′-position in inert terpy ligand on antigenotoxicity, potential antitumor activity and mechanism of interactions of the complexes with biomolecules

The four novel complexes [{cis-PtCl(NH3)2(μ-4,4′-bipy)ZnCl(terpy-Cl)}](ClO4)2, [{trans-PtCl(NH3)2(μ-4,4′-bipyridyl)ZnCl(terpy)}](ClO4)2, [{cis-PtCl(NH3)2(μ-pyrazine)ZnCl(terpy-Cl)}](ClO4)2 and [{trans-PtCl(NH3)2(μ-pyrazine)ZnCl(terpy-Cl)}](ClO4)2 were synthesized and characterized. The chloride in 4′ position of 2,2′:6′,2′′-terpyridine has great influence on the stability of the complexes and their antitumor activity.


The synthesis and characterization of novel hetrometallic complexes [{cis-PtCl(NH3)2(μ-4,4′-bipyridyl)ZnCl(terpy-Cl)}](ClO4)2 (C1a), [{trans-PtCl(NH3)2(μ-4,4′-bipyridyl)ZnCl(terpy)}](ClO4)2 (C2a), [{cis-PtCl(NH3)2(μ-pyrazine)ZnCl(terpy-Cl)}](ClO4)2 (C3a) and [{trans-PtCl(NH3)2(μ-pyrazine)ZnCl(terpy-Cl)}](ClO4)2 (C4a) (where terpy-Cl = 4′-chloro-2,2′:6′,2′′-terpyridine) was done. Acid–base titrations were performed by UV–Vis spectrophotometric method to evaluate the pK a values of corresponding aqua complexes. Interactions between complexes and important biomolecules, guanosine-5′-monophosphate (5′-GMP) and glutathione (GSH) were examined by 1H NMR spectroscopy. The chloride substituent at the 4′ position on the middle pyridine ring of terpyridine ligand significantly affects the coordination of biomolecules, as well as overall stability of complexes. The complexes were evaluated in vitro for the antioxidant prevention of DNA damages. All tested novel complexes demonstrated a significant reduction in DNA damage against oxidative modifications of DNA caused by the hydroxyl and peroxyl radicals. Also, cytotoxicity evaluation showed that significant cytotoxicity occurs only after long-term effect of C1a, C2a and C3a, complexes in HCT-116 cells. Molecular docking studies predict results in agreement with experimental research.

Graphene quantum dots incorporated ZIF‐67 for stabilization of Au nanoparticles: Efficient catalyst for A3‐coupling and nitroarenes reduction reactions

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Graphene quantum dots incorporated ZIF-67 for stabilization of Au nanoparticles: Efficient catalyst for A3-coupling and nitroarenes reduction reactions

Au NPs supported on graphene quantum dots–modified Zeolitic imidazolate framework-67 showed excellent activity and synergetic effect in the reduction of aromatic nitro compounds and A3-coupling reaction of alkynes, amines, and aldehydes in water solvent.


Zeolitic imidazolate framework-67 (ZIF-67) functionalized with graphene quantum dots was prepared and utilized for the reduction of Au (III) and stabilization of Au nanoparticles. This newly prepared ZIF-67/GQD@Au was characterized with different techniques and employed as a capable heterogeneous catalyst for reduction of aromatic nitro compounds and A1-coupling reaction of alkynes, amines, and aldehydes in water solvent. Experiments indicate that this catalyst is able to reduce nitroarenes in short reaction times (10–20 min) in water at room temperature and corresponding amines were obtained in excellent yields (90–100%). Also, reactions of structurally different alkynes, amines, and aldehydes in the presence of this catalyst proceed effectively at 60°C and desired propargylic amine achieved in good to very good yields (76–88%) in water during 1 day. This catalyst displayed excellent stability and recyclability in both reactions and recycled for six runs with a small decrease in the activity.

Synthesis of benzo[b]pyran, 3,4 dihydropyrano[c]chromene and their new furan derivatives using Cu(II) complex of tetradentate Schiff‐base supported on silica as a nanocatalyst

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Synthesis of benzo[b]pyran, 3,4 dihydropyrano[c]chromene and their new furan derivatives using Cu(II) complex of tetradentate Schiff-base supported on silica as a nanocatalyst

The work investigates the synthesis of benzo[b]pyran, 3,4-dihydropyrano[c]chromene and their new furan derivatives using Cu(II) complex of tetradentate Schiff-base supported on silica in aqueous media. The high yields, recyclable catalyst, environmentally benign milder reaction conditions, without need to column chromatography for purification are the main advantages of this method.


Abstract

Cu(II) Complex of tetradentate Schiff-base supported on silica [Cu(II) Schiff-base@-SiO2] catalyzed reactions of aryl aldehydes with carbonyl compounds (dimedon/4-hydroxy coumarin/1,3-cyclohexadion) and malononitrile in aqueous media (H2O:EtOH) to preparation of benzo[b]pyrans and 3,4-dihydropyrano[c]chromanes. Also, using this nanocatalyst, 2-(5-substituted phenyl)furan-2-carboxaldehyde derivatives with carbonyl compounds (dimedon/4-hydroxy coumarin/1,3-cyclohexadion) and malononitrile gave novel tetrahydrobenzo[b]pyran and 3,4-dihydropyrano[c]chromane derivatives in high yields in H2O:EtOH under reflux conditions. The key advantages of this catalytic systems are the formation of novel products, high yields (78%–93%), short reaction time, broad substrate scope, environmentally friendly reaction conditions and also, without need to column chromatography for purification. Furthermore, the nanocatalyst can be reused six times without losing catalytic activity.

Engineering A‐type Dye‐decolorizing Peroxidases by Modification of a Conserved Glutamate Residue

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Dye-decolorizing peroxidases (DyPs) are recently identified microbial enzymes that have been used in several Biotechnology applications from wastewater treatment to lignin valorization. However, their properties and mechanism of action still have many open questions. Their heme-containing active site is buried by three conserved flexible loops with a putative role in modulating substrate access and enzyme catalysis. Here, we investigated the role of a conserved glutamate residue in stabilizing interactions in loop 2 of A-type DyPs. First, we did site saturation mutagenesis of this residue, replacing it with all possible amino acids in bacterial DyPs from Bacillus subtilis (BsDyP) and from Kitasatospora aureofaciens (KaDyP1), the latter being characterized here for the first time. We screened the resulting libraries of variants for activity towards ABTS and identified variants with increased catalytic efficiency. The selected variants were purified and characterized for activity and stability. We furthermore used Molecular Dynamics simulations to rationalize the increased catalytic efficiency and found that the main reason is the electron channeling becoming easier from surface-exposed tryptophans. Based on our findings, we also propose that this glutamate could work as a pH switch in the wild-type enzyme, preventing intracellular damage.

Intermolecular photoinduced electron transfer in biosystems: impact of conformational transitions and multiple channels on kinetics

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Estimating the kinetics of electron transfer (ET) processes in biologically relevant systems using theoretical-computational methods remains a formidable task. This challenge arises from the inherent complexity of these systems, which makes it impractical to apply a fully quantum-mechanical treatment. Hybrid quantum mechanical/classical mechanical computational approaches have been devised to enable the explicit simulation of electron transfer kinetics. This concept article focuses on a specific theoretical-computational method employed in this context, namely the Perturbed Matrix Method (PMM), which has the merit of being able to include large-scale conformational effects in the ET kinetics and potential multiple, alternative, ET channels. We describe its underlying physical principles, examine its advantages and limitations, and offer insights into its applications. Examples of the approach are discussed in the context of estimating photo-induced electron transfer kinetics in proteins. The non-exponential behavior observed in the presented case studies arises mainly from an active coupling with the environment fluctuations, but partly also stems from the presence of branching ET pathways.

Synthesis of 1‐(4‐hydroxybutyl)‐2‐benzoyl indoles from 2‐pyrrolidine benzaldehydes and α‐bromoacetophenones in deep eutectic solvent

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Synthesis of 1-(4-hydroxybutyl)-2-benzoyl indoles from 2-pyrrolidine benzaldehydes and α-bromoacetophenones in deep eutectic solvent

In the absence of organic solvents, catalysts, and other additives, 1-(4-hydroxybutyl)-2-benzoyl indoles were synthesized from 2-pyrrolidine benzaldehydes and α-bromoacetophenones in deep eutectic solvents, underwent cyclization and ring opening processes.


Abstract

A novel and highly efficient method for the synthesis of 1-(4-hydroxybutyl)-2-benzoyl indoles from 2-pyrrolidine benzaldehyde and α-bromoacetophenone in a choline chloride (ChCl)/ZnCl2 eutectic mixture was developed. This method, which does not require any catalyst, additive, or alkali, is useful for realizing tandem cyclization reactions. Several indoles were produced after cyclization and ring opening processes. Not all the compounds obtained are reported in the literature. This synthetic strategy proves that deep eutectic solvents can replace catalysts and organic solvents. Consequently, this is an environmentally friendly strategy that has significant potential in the development of green and sustainable chemistry.

Synthesis of Regioregular and Random Boron‐Fused Azomethine Conjugated Polymers for Film Morphology Control

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Synthesis of Regioregular and Random Boron-Fused Azomethine Conjugated Polymers for Film Morphology Control

Regioregular and random conjugated polymers based on a boron-fused azomethine unit were synthesized. Optical measurements and microscopic observation indicated the existence of aggregation domains in the spin-coated film of the regioregular polymer and no aggregation in that of the regiorandom polymer. Furthermore, fluorescence enhancement was brought about via aggregation disassembly of the regioregular polymer chains by thermal annealing treatment.


Abstract

Regioregular and random conjugated polymers based on a boron-fused azomethine unit were synthesized by Sonogashira–Hagihara cross coupling reaction. Although these polymers exhibited similar optical properties in the solution states, a distinct difference was observed in the aggregation forming ability in the film states; scanning electron microscope (SEM) observation indicated the existence of fiber-like aggregates in the spin-coated film of the regioregular polymer, while regiorandom polymer showed no aggregate in the film state. Accordingly, the UV–vis absorption spectrum of the regioregular polymer showed an increased shoulder peak due to the aggregate formation, whereas the random one showed no change. Furthermore, an absolute fluorescence quantum efficiency of the regioregular polymer was enhanced in response to the aggregate disassembly via thermal annealing treatment. In this study, we demonstrate that controlling regioregularity of the conjugated polymers can induce the different morphological structures and thermal-responsive behaviors. These findings could be beneficial for the design strategy and potential applications of thin-film optoelectronic devices with stimuli-responsive properties.

CNT Sheets Co‐Loaded with Sulfur and Silicon Oxides: Free Standing Anodes for Lithium and Sodium‐Ion Batteries

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CNT Sheets Co-Loaded with Sulfur and Silicon Oxides: Free Standing Anodes for Lithium and Sodium-Ion Batteries

Co-loading of sulfur/silicon oxides in self-supporting binder/collector free CNT sheets delivers enhanced electrochemical storage capacity of 830 mAh g−1 and 368 mAh g−1 at 1 A g−1 current density after 250 cycles in LIB and SIB mode, respectively.


Abstract

Sulfur and silicon oxides loaded self-supporting binder and collector free CNT sheets have been synthesized using floating catalyst chemical vapor deposition technique and investigated for their application as anodes in lithium/sodium ion battery. The CNT sheets have been characterized thoroughly using various microscopic and spectroscopic techniques. The addition of sulfur improves the interplanar spacing in the lattice and also generated abundant defects. The silicon oxides help in enhancing the specific capacity of the CNT sheet via conversion reactions. These features lead to enhanced electrochemical properties and the best performance has been demonstrated by the co-loaded CNT/S/silicon oxide electrode. As anode in LIB, it delivers 830 mAh g−1 at 1 A g−1 current density after 250 cycles. More importantly, the kinetic analysis confirms that sulfur/silicon oxide co-loading can improve the Li+ diffusion coefficient in CNT anode and enhance the metal ion storage. The structural modifications also enhance Na+ ion storage and the CNT/S/Silicon oxide anode delivers 368 mAh g−1 after 250 cycles at a current rate of 1 A g−1 with a superior initial coulombic efficiency of 77.5 %.

Ce‐doped TiO2 fabricated glassy carbon electrode for efficient hydrogen evolution reaction in acidic medium

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The quest for sustainable and clean energy sources has intensified research on the Hydrogen Evolution Reaction (HER) in recent decades. In this study, we present a novel Ce-doped TiO2 catalyst synthesized through the sol-gel method, showcasing its potential as a superior electrocatalyst for HER in an acidic medium. Comprehensive characterization through X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Energy dispersive X-ray (EDX), and Raman spectroscopy confirms the successful formation of the catalyst. Electrocatalytic performance evaluation, including open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), and Tafel analysis, demonstrates that GCE-5wt.%CeTiO2 outperforms bare GCE, as well as Ce and TiO2-based electrodes. Kinetic investigations reveal a Tafel slope of 105 mV dec-1, indicating the Volmer step as the rate-determining step. The onset potential for HER at GCE-5wt.%CeTiO2 is -0.16 V vs. RHE, close to the platinum electrode. Notably, the catalyst exhibits a low overpotential of 401 mV to achieve a current density of 10 mA cm−2 with an impressive 95% Faradaic efficiency. Furthermore, the catalyst demonstrates outstanding durability, maintaining a negligible increase in overpotential during a 14-hour chronoamperometry test. These results have far-reaching implications for the development of cost-effective and efficient electrocatalysts for hydrogen production.