Monthly Archives: September 2023

Exploration of Metal‐Metal Charge Transfer (MMCT) and its Effect in Generating New Colored Compounds in Mixed Metal Oxides

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Exploration of Metal-Metal Charge Transfer (MMCT) and its Effect in Generating New Colored Compounds in Mixed Metal Oxides

Compounds belonging to the palmierite structure (Zn3−xMx)A2O8 (M=Co/Ni/Cu; A=V, P) were prepared and examined for their optical properties. The substitution of bi-valent transition elements in place of Zn2+ ions appear to reduce the band gap and, in a way, akin to band gap engineering. The DFT calculations were carried out to support the findings of the study.


Abstract

Compounds belonging to the palmierite structure, (Zn3−xMx)A2O8 (M=Co, Ni, Cu and A=V, P) have been prepared employing solid state methods. The transition metal substituted compounds of Zn3V2O8 exhibits colors that are unique varying from mint green to forest green for Co2+ ions. The observed colors were understood based on the allowed d-d transitions and metal to metal charge transfer (MMCT) transitions. The MMCT transitions involve partially filled d-orbitals of Co2+ (3d7), Ni2+ (3d8), and Cu2+ (3d9) ions and the V5+ ions (3d0). The spinel compounds, Zn2−xCoxMO4 (M=Ti, Sn) were also prepared to understand the MMCT transitions in the compounds. Band structure calculations were carried out to understand the participating orbitals near the Fermi level and the band gap. The calculations support the idea that the substitution of transition elements in the palmierite structure reduces the overall band gap from 3.18 eV for Zn3V2O8 to 2.61 eV Zn2.5Co0.5V2O8 compound. This indicates the substitution of transition elements provide a tool towards band gap engineering.

Melanin, A Fungal Photosensitizer for Cellulose Oxidizing AA9‐LPMO Enzymes

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Melanin, A Fungal Photosensitizer for Cellulose Oxidizing AA9-LPMO Enzymes

Photosensitation of fungal melanin provides photo-excited electrons and H2O2-cosubstrate to fungal AA9-LPMO enzymes. An example of natural photobiocatalytic system with component sorted all from the same organism.


Abstract

Melanin is a class of hetero-polymer pigments commonly found in nature and widely in fungi. Often referred to as the “animal lignin“, melanin is a very abundant bioresource and features many catalytically interesting properties. We conceived that, upon light absorbance, the polymer could promote long-distance electron donation to fuel redox enzymatic catalysis or controlled in-situ generation of H2O2. Here, we report on a fungal photo-biocatalytic system extracted from the commercially relevant A. nidulans, where photoactivated melanin acts as an electron donor for the cellulose-degrading AnAA9A and TtAA9E metalloenzymes. Furthermore, there was a stable and significant accumulation of H2O2 when melanin was irradiated by visible light; having the peroxide functioning as a co-substrate for the AA9 LPMO enzymes. Oxidized cellulose-derived oligosaccharides were detected in the dark and under light conditions, confirming the potential of melanin to reduce AA9s. When placed under light conditions, they provided hydrogen peroxide as a co-substrate for AA9s. The use of light to tune the in-situ generation of H2O2 by natural pigments might be pivotal to enable also another peroxide-dependent enzymatic catalysis.

Correlating Structure and KA2 Catalytic Activity of ZnII Hydrazone Complexes

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Correlating Structure and KA2 Catalytic Activity of ZnII Hydrazone Complexes

In this manuscript, the synthesis, characterization, and crystal structures of ZnII complexes bearing hydrazone ligands are described. The complexes were evaluated as possible catalysts in the ketone-amine-alkyne coupling reaction. Insights into the catalytic activity of the ZnII complexes were obtained by electronic structure investigations, using DFT calculations.


Abstract

Two new Zn(II) complexes bearing tridentate hydrazone-based ligands with NNO or NNS donor atoms were synthesised and characterised by elemental analysis, infrared (IR) and nuclear magnetic resonance (NMR) spectroscopies, and single crystal X-ray diffraction methods. These complexes, together with four previously synthesised analogues, having hydrazone ligands with a NNO donor set of atoms, were successfully employed as catalysts in the ketone-amine-alkyne (KA2) coupling reaction, furnishing tetrasubstituted propargylamines, compounds with unique applications in organic chemistry. DFT calculations at the CAM-B3LYP/TZP level of theory were performed to elucidate the electronic structure of the investigated Zn(II) complexes, excellently correlating the structure of the complexes to their catalytic reactivity.

Beneficial Effect of Acetic Acid on the Formation of FeIII(OOH) Species and on the Catalytic Activity of Bioinspired Nonheme FeII Complexes.

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Beneficial Effect of Acetic Acid on the Formation of FeIII(OOH) Species and on the Catalytic Activity of Bioinspired Nonheme FeII Complexes.

Three nonheme FeII complexes with pentadentate electron-rich ligands display an enhanced reactivity with H2O2 and improved catalytic properties in the presence of AcOH. The binding of AcOH to the metal center promotes the reaction with the oxidant and leads to the formation of an active species which retains the acetato ligand.


Abstract

Three new amine/pyridine FeII complexes bearing pentadentate ligand with one, two or three electron enriched 4-methoxy-3,5-dimethylpyridine were used as catalysts for the oxidation of small organic molecules by hydrogen peroxide. The distribution of products formed suggests that these ligands are not enough electron donating to promote the O−O heterolytic cleavage of the oxidant in order to generate selective FeV(O) species. Using acetic acid in the reaction mixtures results in a significant increase of the efficiency of these catalytic systems. Our investigations show that the use of AcOH leads to the protonation/dissociation of a pyridyl moiety and the formation of (N4 )FeII(OAc)(OH) species. These complexes readily react with excess hydrogen peroxide to yield (N4 )FeIII(OAc)(OOH) intermediates. These latter intermediates are proposed to evolve into (N4 )FeIV(OAc)(O), which are more efficient than the usual (N4 )FeIV(O) and (N5 )FeIV(O).

Iron Cobalt Phosphonate Derived Heteroatom Doped Metal Oxides as Superior Electrocatalysts for Water Oxidation Reaction

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Iron Cobalt Phosphonate Derived Heteroatom Doped Metal Oxides as Superior Electrocatalysts for Water Oxidation Reaction

Porous metal phosphonates and their oxide derivatives for electrochemical water oxidation: four different transition metal-based oxides have been synthesized under pyrolysis which have been explored for electrochemical water oxidation reaction in alkaline KOH solution.


Abstract

The development of low cost-effective and highly efficient heterogeneous electrocatalysts is most appreciable in the research community. A newly designed microporous organic-inorganic hybrid iron cobalt phosphonate (FeCoDPAM) is synthesized using diphenylphosphinamide as an organophosphorus ligand through a hydrothermal pathway without any template. To synthesize N, P-codoped bimetallic oxides (NP/FeCoO350, NP/FeCoO550, and NP/FeCoO750), the as-synthesized material FeCoDPAM has undergone pyrolysis at three different temperatures, i. e., 350, 550, 750 °C, respectively. The high specific surface area and a regular microporous array of N, P-codoped iron cobalt oxide (NP/FeCoO350) material provide excellent oxygen evolution reaction (OER) activity. The NP/FeCoO350 material catalyzes OER with the overpotential of 331 mV at a current density of 10 mAcm−2 and Tafel slope of 56.7 mV dec−1 in 1.0 M KOH solution. The inclusion of iron in the cobalt phosphonate framework can change the electronic structure, and electron transfer can be feasible to the d-orbital of cobalt. Due to the doping of heteroatoms such as N and P into the bimetallic oxide matrix, a synergistic effect can occur, which is the driving force for the efficient electrocatalytic OER activity. Also, the FeCoO350 displays stability with outstanding oxidative current up to 50 h time in chronoamperometry measurement.

Unlocking Synergistic Potential: Agomelatine Enhances the Chemotherapeutic Effect of Paclitaxel in Breast Cancer Cell Through MT1 Melatonin Receptors and ER‐alpha Axis

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Unlocking Synergistic Potential: Agomelatine Enhances the Chemotherapeutic Effect of Paclitaxel in Breast Cancer Cell Through MT1 Melatonin Receptors and ER-alpha Axis


Abstract

This study investigates the potential of agomelatine (AGO), a synthetic melatoninergic drug, in combination with paclitaxel (PTX) for the treatment of breast cancer. The effects of AGO, PTX and melatonin (MTN) on breast cancer cell viability were investigated, focusing on the role of MT1 receptors. Cell viability and gene expression were analyzed in MCF-7 and MDA-MB-231 breast cancer cell experiments. The results show that AGO has cytotoxic effects on breast cancer cells similar to MTN. Combining AGO and MTN with PTX showed synergistic effects in MCF-7 cells. The study also reveals differences in the molecular mechanisms of breast cancer between estrogen-positive MCF-7 cells and estrogen-negative MDA-MB-231 cells. Combination with AGO and PTX affects apoptosis-associated proteins in both cell types. The findings suggest that AGO, combined with PTX, may be a promising adjuvant therapy for breast cancer and highlight the importance of MTN receptors in its mechanism of action.

Modeling of the Bioleaching of Process Silver Pulp

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Modeling of the Bioleaching of Process Silver Pulp

A new model for the bioleaching process of silver is used to theoretically describe available experimental data. The model is based on the two-moving-front description of mineral bioleaching. The model quantitatively predicts the evolution of the silver mass fraction and the minimum in the biofilm mass fraction, related to the maximum in the rheological properties.


Abstract

Modeling of the bioleaching process applied to the system silver-manganese (Ag-Mn) was carried out. The two-moving-fronts model was used to describe the main stages of the process. Bioleaching involves a catalytic process carried out by bacteria to dissolve the mineral ores. Initially, the bacteria interact with the mineral to dissolve manganese, leading to the precipitation of silver. The Ag-Mn compound is dissolved by the bacteria in two stages. First, the bacteria dissolve the manganese and form a biofilm composed mostly of exopolysaccharides. In the second stage, the biofilm is consumed by the bacteria, ending up in dissolved manganese and silver precipitation. At 48 h, the viscosity of the pulp reaches a maximum attributed to the maximum concentration of extracellular polysaccharides in the medium. Predictions describe the basic issues of the bioleaching process in this system.

Thixotropic Hydrogels Based on Laponite® and Cucurbituril for Delivery of Lipophilic Drug Molecules

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Nowadays the use of hydrogels for biomedical purposes is increasing because of their interesting features that allow the development of targeted drug delivery systems. Herein, hydrogel based on Laponite (Lap) clay mineral as gelator and cucurbit[6]uril (CB[6]) molecules were synthetized for the delivery of flufenamic acid (FFA) for potential topical application. Firstly, the interaction between CB[6] and FFA was assessed by UV-vis spectroscopic measurements and computational calculations. Then, the obtained complex was used as filler for Lap hydrogel (Lap/CB[6]/FFA). The properties of the hydrogel in terms of viscosity and, self-repair abilities were investigated; their morphology was imaged by scanning electron and polarized optical microscopies. Furthermore, the changes in the hydrodynamic radii and in the colloidal stability of CB[6]/Lap mixture were investigated in terms of translational diffusion from dynamic light scattering and z-potential measurements. Finally, the kinetic in vitro release of FFA, from Lap/CB[6]/FFA hydrogel, was studied in a medium mimicking the pH of skin and the obtained results were discussed both by an experimental point of view and by computational calculations.