CO2-Driven N-Formylation/N-Methylation of Amines Using C-Scorpionate Metal Complexes

C-scorpionate metal complexes, specifically, [NiCl2(tpm)]·3H2O, [CoCl2(tpm)]·3H2O and [PdCl2(tpm)] [tpm = hydrotris(1H-pyrazol-1-yl)methane], were effective in the N-formylation and N-methylation of amines using carbon dioxide, as carbon source, in the presence of sodium borohydride. Various parameters were studied, including reaction time, temperature, solvent volume, presence of additives, and catalyst amount. These parameters were found to have a significant impact on the selectivity of the product. [NiCl2(tpm)]·3H2O exhibited good conversion at 80 °C, but its selectivity towards formamide decreased with prolonged reaction time. Increasing the amount of [NiCl2(tpm)]·3H2O, the selectivity changed. [PdCl2(tpm)] showed different selectivity compared to [NiCl2(tpm)]·3H2O, while [CoCl2(tpm)]·3H2O presented poor results. Monitoring the reaction course by 1H NMR revealed the presence of an intermediate species that influenced product formation. These results highlight the versatility and catalytic potential of C-scorpionate metal complexes in the N-formylation/N-methylation of amines in the catalytic system (NaBH4/MeCN/CO2).

The reaction of acetonitrile with hydrogen peroxide in alkaline medium: a DFT mechanistic study of green production of amides

We have investigated using DFT methods the reaction mechanism of the Radzisewski reaction to obtain an amide via the reaction of ACN and H2O2 under alkaline conditions. The direct reaction between ACN and H2O2 showed a quite high activation energy (about 45 kcal mol-1) rendering this path unreliable. Instead, a fast reaction between ACN and HOO- forming the deprotonated species (PAIA-) of the peroxyacetimidic acid (PAIA) was observed. From this, PAIA- was guessed to form PAIA through a fast reaction of hydrolysis. Moreover, a second way of formation of PAIA, through an OH- catalyzed path, made the rate determining step (RDS) in very good agreement with experimental data, hence neglecting the contribution of the kinetically favored hydrolysis of PAIA-. This discrepancy was reconciled by considering that the final amide was obtained through a regioselective path forming the PAIA and the further reaction involving the decomposition of PAIA and PAIA-. Indeed, the PAIA obtained from the hydrolysis reaction showed a configuration which did not match the configurational behavior required. Conversely, the PAIA formed from the RDS path matched the required configuration needed to obtain the amide. Our findings also disentangled the experimenal debate on the assignment of the RDS.

Correction: The reaction of acetonitrile with hydrogen peroxide in alkaline medium: a DFT mechanistic study of green production of amides

Correction for 'The reaction of acetonitrile with hydrogen peroxide in alkaline medium: a DFT mechanistic study of green production of amides' by Girolamo Casella et al., Phys. Chem. Chem. Phys., 2023, https://doi.org/10.1039/d3cp02024j.

Exploring the Mechanisms behind the Anti-Tumoral Effects of Model C-Scorpionate Complexes

The growing worldwide cancer incidence, coupled to the increasing occurrence of multidrug cancer resistance, requires a continuous effort towards the identification of new leads for cancer management. In this work, two C-scorpionate complexes, [FeCl₂(κ³-Tpm)] (1) and [Co(κ³-Tpm^OH)₂](NO₃)₂ (2), (Tpm = hydrotris(pyrazol-1-yl)methane and Tpm^OH = 2,2,2-tris(pyrazol-1-yl)ethanol), were studied as potential scaffolds for future anticancer drug development. Their cytotoxicity and cell migration inhibitory activity were analyzed, and an untargeted metabolomics approach was employed to elucidate the biological processes significantly affected by these two complexes, using two tumoral cell lines (B16 and HCT116) and a non-tumoral cell line (HaCaT). While [FeCl₂(κ³-Tpm)] did not display a significant cytotoxicity, [Co(κ³-Tpm^OH)₂](NO₃)₂ was particularly cytotoxic against the HCT116 cell line. While [Co(κ³-Tpm^OH)₂](NO₃)₂ significantly inhibited cell migration in all tested cell lines, [FeCl₂(κ³-Tpm)] displayed a mixed activity. From a metabolomics perspective, exposure to [FeCl₂(κ³-Tpm)] was associated with changes in various metabolic pathways involving tyrosine, where iron-dependent enzymes are particularly relevant. On the other hand, [Co(κ³-Tpm^OH)₂](NO₃)₂ was associated with dysregulation of cell adhesion and membrane structural pathways, suggesting that its antiproliferative and anti-migration properties could be due to changes in the overall cellular adhesion mechanisms.

Effect of Graphene vs. Reduced Graphene Oxide in Gold Nanoparticles for Optical Biosensors-A Comparative Study

Aiming to develop a nanoparticle-based optical biosensor using gold nanoparticles (AuNPs) synthesized using green methods and supported by carbon-based nanomaterials, we studied the role of carbon derivatives in promoting AuNPs localized surface plasmon resonance (LSPR), as well as their morphology, dispersion, and stability. Carbon derivatives are expected to work as immobilization platforms for AuNPs, improving their analytical performance. Gold nanoparticles (AuNPs) were prepared using an eco-friendly approach in a single step by reduction of HAuCl₄·3H₂O using phytochemicals (from tea) which act as both reducing and capping agents. UV-Vis spectroscopy, transmission electron microscopy (TEM), zeta potential (ζ-potential), and X-ray photoelectron spectroscopy (XPS) were used to characterize the AuNPs and nanocomposites. The addition of reduced graphene oxide (rGO) resulted in greater dispersion of AuNPs on the rGO surface compared with carbon-based nanomaterials used as a support. Differences in morphology due to the nature of the carbon support were observed and are discussed here. AuNPs/rGO seem to be the most promising candidates for the development of LSPR biosensors among the three composites we studied (AuNPs/G, AuNPs/GO, and AuNPs/rGO). Simulations based on the Mie scattering theory have been used to outline the effect of the phytochemicals on LSPR, showing that when the presence of the residuals is limited to the formation of a thin capping layer, the quality of the plasmonic resonance is not affected. A further discussion of the application framework is presented.

Efficient and Reusable Iron Catalyst to Convert CO2 into Valuable Cyclic Carbonates

The production of cyclic carbonates from CO2 cycloaddition to epoxides, using the C-scorpionate iron(II) complex [FeCl2{κ3-HC(pz)3}] (pz = 1H-pyrazol-1-yl) as a catalyst, is achieved in excellent yields (up to 98%) in a tailor-made ionic liquid (IL) medium under mild conditions (80 °C; 1-8 bar). A favorable synergistic catalytic effect was found in the [FeCl2{κ3-HC(pz)3}]/IL system. Notably, in addition to exhibiting remarkable activity, the catalyst is stable during ten consecutive cycles, the first decrease (11%) on the cyclic carbonate yield being observed during the 11th cycle. The use of C-scorpionate complexes in ionic liquids to afford cyclic carbonates is presented herein for the first time.

Application of Ionic Liquids in Electrochemistry-Recent Advances

In this review, the roles of room temperature ionic liquids (RTILs) and RTIL based solvent systems as proposed alternatives for conventional organic electrolyte solutions are described. Ionic liquids are introduced as well as the relevant properties for their use in electrochemistry (reduction of ohmic losses), such as diffusive molecular motion and ionic conductivity. We have restricted ourselves to provide a survey on the latest, most representative developments and progress made in the use of ionic liquids as electrolytes, in particular achieved by the cyclic voltammetry technique. Thus, the present review comprises literature from 2015 onward covering the different aspects of RTILs, from the knowledge of these media to the use of their properties for electrochemical processes. Out of the scope of this review are heat transfer applications, medical or biological applications, and multiphasic reactions.

Catalytic Performance of a Magnetic Core-Shell Iron(II) C-Scorpionate under Unconventional Oxidation Conditions

For the first time, herein is reported the use of a magnetic core-shell support for a C-scorpionate metallic complex. The prepared hybrid material, that consists on the C-scorpionate iron(II) complex [FeCl₂{κ³-HC(pz)₃}] (pz, pyrazolyl) immobilized at magnetic core-shell particles (Fe₃O₄/TiO₂), was tested as catalyst for the oxidation of secondary alcohols using the model substrate 1-phenylethanol. Moreover, the application of alternative energy sources (e.g., ultrasounds, microwaves, mechanical or thermal) for the peroxidative alcohol oxidation using the magnetic heterogenized iron(II) scorpionate led to different/unusual outcomes that are presented and discussed.

Green synthesis of zinc oxide particles with apple-derived compounds and their application as catalysts in the transesterification of methyl benzoates

ZnO nanoparticles (ZnONPs) were successfully synthesized using bravo-de-esmolfe apple extract in aqueous medium at room temperature. ZnO microparticles, prepared with a pure apple phytochemical, quercetin (ZnOq), or without phytochemicals (ZnO) were studied for comparative purposes. The re-use of apple waste for highly efficient catalyst production, based on green synthetic routes, can be added to the concept of a circular economy. The synthesized ZnO particles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and N2 adsorption/desorption Brunauer-Emmett-Teller (BET) theory. The XRD patterns indicated the formation of a hexagonal wurtzite phase with high purity and SEM and TEM analyses revealed the morphology of the particles. The apple extract produced spherical ZnONPs composed of round lamina-like structures, similar to the micro sized lamina-like shape of ZnOq and dissimilar to the flower-like shape of ZnO. The green synthesized ZnO nanoparticles (ZnONPs) led to a high product yield of ca. 96% within 24 h of reaction time in the transesterification reaction of different carboxylic esters.

Ultrasound and Radiation-Induced Catalytic Oxidation of 1-Phenylethanol to Acetophenone with Iron-Containing Particulate Catalysts

Iron-containing particulate catalysts of 0.1–1 µm size were prepared by wet and ball-milling procedures from common salts and characterized by FTIR, TGA, UV-Vis, PXRD, FEG-SEM, and XPS analyses. It was found that when the wet method was used, semi-spherical magnetic nanoparticles were formed, whereas the mechanochemical method resulted in the formation of nonmagnetic microscale needles and rectangles. Catalytic activity of the prepared materials in the oxidation of 1-phenylethanol to acetophenone was assessed under conventional heating, microwave (MW) irradiation, ultrasound (US), and oscillating magnetic field of high frequency (induction heating). In general, the catalysts obtained by wet methods exhibit lower activities, whereas the materials prepared by ball milling afford better acetophenone yields (up to 83%). A significant increase in yield (up to 4 times) was observed under the induction heating if compared to conventional heating. The study demonstrated that MW, US irradiations, and induction heating may have great potential as alternative ways to activate the catalytic system for alcohol oxidation. The possibility of the synthesized material to be magnetically recoverable has been also verified.

Supported Gold Nanoparticles as Catalysts in Peroxidative and Aerobic Oxidation of 1-Phenylethanol under Mild Conditions

The efficiency of Au/TiO₂ based catalysts in 1-phenylethanol oxidation was investigated. The role of support modifiers (La₂O₃ or CeO₂), influence of gold loading (0.5% or 4%) and redox pretreatment atmosphere, catalyst recyclability, effect of oxidant: tert-butyl hydroperoxide (TBHP) or O₂, as well as the optimization of experimental parameters of the reaction conditions in the oxidation of this alcohol were studied and compared with previous studies on 1-octanol oxidation. Samples were characterized by temperature-programmed oxygen desorption (O₂-TPD) method. X-ray photoelectron spectroscopy (XPS) measurements were carried out for used catalysts to find out the reason for deactivation in 1-phenylethanol oxidation. The best catalytic characteristics were shown by catalysts modified with La₂O₃, regardless of the alcohol and the type of oxidant. When O₂ was used, the catalysts with 0.5% Au, after oxidative pretreatment, showed the highest activity in both reactions. The most active catalysts in 1-phenylethanol oxidation with TBHP were those with 4% Au and the H₂ treatment, while under the same reaction conditions, 0.5% Au and O₂ treatment were beneficial in 1-octanol oxidation. Despite the different chemical nature of the substrates, it seems likely that Au⁺(Au^δ+) act as the active sites in both oxidative reactions. Density functional theory (DFT) simulations confirmed that the gold cationic sites play an essential role in 1-phenylethanol adsorption.

Ionic liquid-based nanofluids (ionanofluids) for thermal applications: an experimental thermophysical characterization

Heat transfer fluids materials are manufactured for the purpose of transfer, distribution and storage of heat. Several of their important properties can be listed (for example flash point, thermal expansivity or technical safety). However, to assess the thermal exchange performance of these fluids, a prior knowledge of their heat capacity, density, viscosity and thermal conductivity is obligatory. The most popular heat transfer fluids are based on organic liquids, such as ethylene glycol. However, new technologies and development require more efficient materials. Ionanofluids, mixtures of ionic liquids and nanoparticles, were proposed as a viable replacement for those commonly used fluids due to the properties of ionic liquids (wide liquid range or low vapour pressure and flammability) combined with enhanced thermophysical properties of nanofluids caused by the dispersion of nanoparticles (mainly thermal conductivity and heat capacity). Very few authors reported the extensive analysis of those systems thermophysical properties and impact on the heat exchange efficiency. Moreover, the availability of published data is very limited. The aim of this work is to investigate ionanofluids based on the trihexyl(tetradecyl)phosphonium cation paired with the acetate, butanoate, hexanoate, octanoate or decanoate anion, mixed with carbon nanotubes, boron nitride, graphite or mesoporous carbon as nanoparticles with concentration up to 3 wt %. The density, heat capacity, thermal stability, thermal conductivity and viscosity of selected ionanofluids were determined experimentally as functions of the temperature (up to 363.15 K) and compared with theoretical tools to evaluate the predictive capability. Based on the experimental results, lubrication, heat storage potential and economic analysis were also discussed and compared to commercial heat transfer fluids.

Synergistic catalytic action of vanadia–titania composites towards the microwave-assisted benzoin oxidation

Application of synergistic effects is among the main ways to boost chemical efficiency.

Thermal Conductivity Enhancement Phenomena in Ionic Liquid-Based Nanofluids (Ionanofluids)

The dispersion of nanoparticles into ionic liquids leads to enhancement of their thermal conductivity. Several papers report on various enhancement values, whereas the comparison between these values with those from theoretical calculations is not always performed. These thermal conductivity enhancements are desired due to their beneficial impact on heat transfer performance in processes requiring the utilisation of heat transfer fluids. Moreover, on the one hand, the theoretical modelling of these enhancements might lead to an easier, cheaper, and faster heat transfer unit design, which could be an enormous advantage in the design of novel industrial applications. On the other hand, it significantly impacts the enhancement mechanism. The aim of this work is to discuss the enhancement of thermal conductivity caused by the dispersion of nanoparticles in ionic liquids, including the analysis of their errors, followed by its theoretical modelling. Furthermore, a comparison between the data reported herein with those available in the literature is carried out following the reproducibility of the thermal conductivity statement. The ionic liquids studied were 1-butyl-3-methylimidazolium dicyanamide, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazolium ethylsulfate, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, and 1-hexyl-3-methylimidazolium hexafluorophosphate, while carbon nanotubes, boron nitride, and graphite were selected as nanoparticles to be dispersed in the investigated ionic liquids to design novel heat transfer fluids.

Comparison of microwave and mechanochemical energy inputs in the catalytic oxidation of cyclohexane

The effect of microwave and mechanochemical ball milling energy inputs was studied for the peroxidative oxidation (with aqueous H2O2) of cyclohexane to cyclohexanol and cyclohexanone, over CoCl2 and/or V2O5 dispersed (μm scale) catalysts. A maximum total yield of cyclohexanol and cyclohexanone of 43% after 1 h of reaction at 30 °C, in acetonitrile and under microwave irradiation (5 W), was achieved over the CoCl2-V2O5 (3 : 1) catalyst prepared by ball milling. Cyclohexanol is the main final product with a selectivity of up to 93% over cyclohexanone. Conducting the oxidation reaction under microwave irradiation under the same conditions but without any mechanochemical treatment of the catalyst prior to use resulted in a lower total yield of 30% with a lower selectivity (69%) towards cyclohexanol over cyclohexanone. The sole application of mechanochemical treatment for the catalyst preparation and the catalytic oxidation of cyclohexane allowed to reach yields of 29% after 1 h of reaction, at room temperature, without microwave irradiation and any additive and in the absence of any organic solvent. Ball milling is shown to provide a convenient, solvent-free method to disperse these solid catalysts and to promote the above cyclohexane oxidation, although, in the latter case, not so effectively as microwave irradiation.

Effect of Phenolic Compounds on the Synthesis of Gold Nanoparticles and its Catalytic Activity in the Reduction of Nitro Compounds

Gold nanoparticles (AuNPs) were prepared using an eco-friendly approach in a single step by reduction of HAuCl₄ with polyphenols from tea extracts, which act as both reducing and capping agents. The obtained AuNPs were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet–visible spectroscopy (UV–vis), and X-ray photoelectron spectroscopy (XPS). They act as highly efficient catalysts in the reduction of various aromatic nitro compounds in aqueous solution. The effects of a variety of factors (e.g., reaction time, type and amount of reducing agent, shape, size, or amount of AuNPs) were studied towards the optimization of the processes. The total polyphenol content (TPC) was determined before and after the catalytic reaction and the results are discussed in terms of the tea extract percentage, the size of the AuNPs, and their catalytic activity. The reusability of the AuNP catalyst in the reduction of 4-nitrophenol was also tested. The reactions follow pseudo first-order kinetics.

Evaluation of cell toxicity and DNA and protein binding of green synthesized silver nanoparticles

Silver nanoparticles (AgNPs) were prepared by GREEN chemistry relying on the reduction of AgNO₃ by phytochemicals present in black tea extract. AgNPs were fully characterized by transmission electron microscopy (TEM), ultraviolet-visible spectroscopy ((UV-vis)), X-ray diffraction (XRD) and energy dispersive absorption spectroscopy (EDS). The synthesized AgNPs induced a decrease of the cell viability in a dose-dependent manner with a low IC₅₀ (0.5 ± 0.1 μM) for an ovarian carcinoma cell line (A2780) compared to primary human fibroblasts (IC₅₀ 5.0 ± 0.1 μM). The DNA binding capability of CT (calf thymus) DNA was investigated using electronic absorption and fluorescence spectroscopies, circular dichroism and viscosity titration methods. Additionally, the AgNPs strongly quench the intrinsic fluorescence of BSA, as determined by synchronous fluorescence spectra.

Highly efficient and reusable CNT supported iron(ii) catalyst for microwave assisted alcohol oxidation

The highly efficient eco-friendly synthesis of ketones (yields over 99%) from secondary alcohols is achieved by combination of [FeCl2{η(3)-HC(pz)3}] (pz = pyrazol-1-yl) supported on functionalized multi-walled carbon nanotubes and microwave irradiation, in a solvent-free medium. The carbon homoscorpionate iron(ii) complex is the first one of this class to be used as catalyst for the oxidation of alcohols.

Mononuclear copper(ii) complexes of an arylhydrazone of 1H-indene-1,3(2H)-dione as catalysts for the oxidation of 1-phenylethanol in ionic liquid medium

Cu^II complexes of an arylhydrazone of 1H-indene-1,3(2H)-dione act as homogeneous catalysts for the microwave-assisted peroxidative oxidation of alcohols in ionic liquid medium.

A Cu(ii) MOF with a flexible bifunctionalised terpyridine as an efficient catalyst for the single-pot hydrocarboxylation of cyclohexane to carboxylic acid in water/ionic liquid medium

A bifunctionalised terpyridine based Cu(ii) MOF for efficient hydrocarboxylation of cyclohexane to cyclohexanecarboxylic acid in an ionic liquid medium.

Nickel(ii)-2-amino-4-alkoxy-1,3,5-triazapentadienate complexes as catalysts for Heck and Henry reactions

Nickel(ii)-triazapentadienate complexes are synthesized and found to act as catalysts in the Heck and Henry reactions.

ZnII and CdII MOFs based on an amidoisophthalic acid ligand: synthesis, structure and catalytic application in transesterification

Metal–organic frameworks of Zn(ii) and Cd(ii) act as recyclable heterogeneous catalysts for the transesterification reaction of carboxylate esters.

Syntheses and crystal structures of benzene-sulfonate and -carboxylate copper polymers and their application in the oxidation of cyclohexane in ionic liquid under mild conditions

Enhanced catalytic activities of copper polymers for the peroxidative oxidation of cyclohexane are observed in an ionic liquid medium.

Reduced Graphene Oxide Composite with Oxidizable Manganese/Cobalt Mixed Oxide for p-Cresol Oxidation by Using Molecular Oxygen

A composite of graphene oxide (GO) with mixed oxide (MnCo) was prepared by using a solvothermal method. During the synthesis, both the reduction of GO and growth of metal oxides took place simultaneously. The as-prepared composite material was highly selective for the liquid-phase oxidation of p-cresol to form p-hydroxybenzaldehyde in 71 % yield within 1 h. The composite material was characterised by SEM, X-ray photoelectron spectroscopy, high-resolution TEM and cyclic voltammetry (CV). A CV study revealed that the increase in the redox potential of the mixed oxide after being supported on GO, led to its higher activity of the catalyst for the oxidation reaction. The stability of the catalyst under the reaction conditions was studied by its successful reuse in three cycles.

Effects of hormonal supplementation on nuclear maturation and cortical granules distribution of canine oocytes during various reproductive stages

The aim of this study was to evaluate the effects of hCG, progesterone and oestradiol supplementation on nuclear and cytoplasmic maturation of canine oocytes cultured for 24, 48, 72 and 96 h. Oocytes obtained from 18 healthy bitches were divided into three groups according to their reproductive status (follicular, luteal and anoestrus stages) and cultured in TCM 199 + 25 UI/ml of hCG + 1 μg/ml of progesterone + 1 μg/ml of 17-β oestradiol or without hormonal supplementation (control) for different periods. Then, they were stained with FITC-LCA-Hoescht for chromatin configuration and cortical granules distribution and evaluated under an epifluorescence microscope. Culture time and the influence of different stages of the oestrous cycle were also evaluated. The present study demonstrated that there was no significant difference among the reproductive stages. With regards to culture medium, only oocytes from the supplemented medium were able to complete meiosis; however, significant difference was only noticed in the percentage of MI stage oocytes (p < 0.05) in the follicular and luteal group at 72 h of culture. Most oocytes in germinal vesicle, germinal vesicle breakdown and metaphase I stage had cortical granules distributed throughout the cytoplasm (immature pattern), irrespective of the culture period (p < 0.05). Cortical granules distributed immediately beneath the plasma membrane (mature) was only observed in metaphase II stage oocytes, but not all of them presented matured cytoplasm. Our results reveal that cortical granules distribution in canine oocytes matured in vitro did not progressed in correspondence with nuclear stage changes and are in accordance with those from other species.