Catalytic, Antifungal, and Antiproliferative Activity Studies of a New Family of Mononuclear [VIVO]/[VVO2] Complexes

Ligands derived from 2-(1-phenylhydrazinyl)pyridine and salicylaldehyde (HL1), 3-methoxysalicylaldehyde (HL2), 5-bromosalicylaldehyde (HL3), and 3,5-di-tert-butylsalicylaldehyde (HL4) react with [VIVO(acac)2] in MeOH followed by aerial oxidation to give [VVO2(L1)] (1), [VVO2(L2)] (2), [VVO2(L3)] (3), and [VVO2(L4)] (4). Complex [VIVO(acac)(L1)] (5) is also isolable from [VIVO(acac)2] and HL1 in dry MeOH. Structures of all complexes were confirmed by single-crystal X-ray and spectroscopic studies. They efficiently catalyze benzyl alcohol and its derivatives' oxidation in the presence of H2O2 to their corresponding aldehydes. Under optimized reaction conditions using 1 as a catalyst precursor, conversion of benzyl alcohol follows the order: 4 (93%) > 2 (90%) > 1 (86%) > 3 (84%) ≈ 5 (84%). These complexes were also evaluated for antifungal and antiproliferative activities. Complex 3 with MIC50 = 16 μg/mL, 4 with MIC50 = 12 μg/mL, and 5 with MIC50 = 16 μg/mL are efficient toward planktonic cells of Candida albicans and Candida tropicalis. On Michigan cancer foundation-7 (MCF-7) cells, they show comparable cytotoxic effects and exhibit IC50 in the 27.3-33.5 μg/mL range, and among these, 4 exhibits the highest cytotoxicity. A similar study on human embryonic kidney cells (HEK293) confirms their less toxicity at lower concentrations (4 to 16 μg/mL) compared to MCF-7.

Oxidant-Free Electrochemical Direct Oxidative Benzyl Alcohols to Benzyl Aldehydes Using Three-Dimensional Printing PPAR Polyoxometalate

The oxidation of benzyl alcohols is an important reaction in organic synthesis. Traditional methods for benzyl alcohol oxidation have not been widely utilized due to the use of significant amounts of precious metals and environmentally unfriendly reagents. In recent years, electrocatalytic oxidation has gained significant attention, particularly electrochemical anodic oxidation, which offers a sustainable alternative for oxidation without the need for external oxidants or reducing agents. Here, a copper monosubstituted phosphotungstate-based polyacrylate resins (Cu-LPOMs@PPAR) catalyst has been fabricated with immobilization and recyclability using 3D printing technology that can be successfully applied in the electrocatalytic oxidation of benzyl alcohol to benzaldehyde, achieving atom economy and reducing pollution. In this protocol, we obtain benzaldehyde in good yields with excellent functional group toleration under metal-free and oxidant-free conditions. This strategy could provide a new avenue for heterogeneous catalysts in application for enhancing the efficiency and selectivity of electrocatalytic oxidation processes.

Selective Oxidation of Tetrahydrofuran to Gamma-Butyrolactone over Spinel ZnFe2O4 Nanoparticle Catalyst

The selective oxidation of tetrahydrofuran (THF) to gamma-butyrolactone (GBL) on spinel ZnFe2O4 nanoparticles (ZFNPs) was investigated. The catalyst was prepared with the coprecipitation method and characterized by FTIR, XRD, TEM, SEM, EDS, TGA, XPS, and BET surface area. The characterization techniques showed that a nonuniform spherical spinal oxide with an average particle size of 26 nm was formed. The oxidation reaction was carried out using hydrogen peroxide as an oxidizing agent under solvent-free conditions. GC-MS analysis revealed that the main product was GBL. 2-hydroxytetrahydrofuran (THF-2-OH), gamma-hydroxybutyric acid (GHBA), and gamma-hydroxybutaldehyde (GHBAl) were obtained as minor products. The effects of different reaction parameters, such as temperature, H2O2/THF mole ratio, catalyst dose, reaction time, and reusability, were evaluated. A 47.3% conversion of THF with an 88.2% selectivity of GBL was achieved by conducting the reaction at 80 °C for nine hours using a 1:1 mole ratio of H2O2/THF. A slight increase in the conversion degree was attained at higher temperatures; however, an over-oxidation process was observed as the temperature exceeded 80 °C. The catalyst remained effective and stable over four reuses.

A Direct Catalytic Ethanol Fuel Cell (DCEFC) Modified by LDHs, or by Catalase-LDHs, and Improvement in Its Kinetic Performance: Applications for Human Saliva and Disinfectant Products for COVID-19

In this work, it has been experimentally proven that the kinetic performance of a common Direct Catalytic Ethanol Fuel Cell (DCEFC) can be increased by introducing nanostructured (Zn^II,Al^III(OH)₂)⁺NO₃^-·H₂O Layered Double Hydroxides (LDHs) into the anode compartment. Carrying out the measurements with the open-circuit voltage method and using a kinetic format, it has been shown that the introduction of LDHs in the anodic compartment implies a 1.3-fold increase in the calibration sensitivity of the method. This improvement becomes even greater in the presence of hydrogen peroxide in a solution. Furthermore, we show that the calibration sensitivity increased by 8-times, when the fuel cell is modified by the enzyme catalase, crosslinked on LDHs and in the presence of hydrogen peroxide. The fuel cell, thus modified (with or without enzyme), has been used for analytical applications on real samples, such as biological (human saliva) and hand disinfectant samples, commonly used for the prevention of COVID-19, obtaining very positive results from both analytical and kinetic points of view on ethanol detection. Moreover, if the increase in the calibration sensitivity is of great importance from the point of view of analytical applications, it must be remarked that the increase in the speed of the ethanol oxidation process in the fuel cell can also be extremely useful for the purposes of improving the energy performance of a DCEFC.

Tetra-n-butylammonium decatungstate supported on Fe3O4 nanoparticles: a novel nanocatalyst for green synthesis of nitroso compounds

The Fe3O4/TBADT composite catalyst (M-DT) can efficiently oxidize aromatic amine compounds selectively into nitroso compounds in the presence of H2O2. The high efficiency is due to the strong interaction between Fe3O4 and TBADT.

Low Platinum-Content Electrocatalysts for Highly Sensitive Detection of Endogenously Released H2O2

The commercial viability of electrochemical sensors requires high catalytic efficiency electrode materials. A sluggish reaction of the sensor’s primary target species will require a high overpotential and, consequently, an excessive load of catalyst material to be used. Therefore, it is essential to understand nanocatalysts’ fundamental structures and typical catalytic properties to choose the most efficient material according to the biosensor target species. Catalytic activities of Pt-based catalysts have been significantly improved over the decades. Thus, electrodes using platinum nanocatalysts have demonstrated high power densities, with Pt loading considerably reduced on the electrodes. The high surface-to-volume ratio, higher electron transfer rate, and the simple functionalisation process are the main reasons that transition metal NPs have gained much attention in constructing high-sensitivity sensors. This study has designed to describe and highlight the performances of the different Pt-based bimetallic nanoparticles and alloys as an enzyme-free catalytic material for the sensitive electrochemical detection of H₂O₂. The current analysis may provide a promising platform for the prospective construction of Pt-based electrodes and their affinity matrix.