Diverse Catalytic Activity Research Articles

Application of the nanostructured R-AgLAFE electrode to study the electroreduction process of Bi(III) ions in the presence of N-acetylcysteine

Bi(III) ions electroreduction in the presence of N-acetylcysteine (ACYS)at the nanostructured R-AgLAFE electrode has been studied by the voltammetric and impedance measurements. The experimental data indicates the multistage character of the electrode process and the catalytic influence of N-acetylcysteine on the Bi(III) ions electroreduction rate. It was found that this process is controlled by the chemical reaction of the Bi(III)–Hg(SR)2 activecomplexes formation on the electrode surface, which mediates electron transfer. Active complexes are a substrate in the process of electroreduction, and their different structure and properties are the reason for the diverse catalytic activity of N-acetylcysteine.

Environmental and Pharmacokinetic Aspects of Zeolite/Pharmaceuticals Systems—Two Facets of Adsorption Ability

Zeolites belong to aluminosilicate microporous solids, with strong and diverse catalytic activity, which makes them applicable in almost every kind of industrial process, particularly thanks to their eco-friendly profile. Another crucial characteristic of zeolites is their tremendous adsorption capability. Therefore, it is self-evident that the widespread use of zeolites is in environmental protection, based primarily on the adsorption capacity of substances potentially harmful to the environment, such as pharmaceuticals, pesticides, or other industry pollutants. On the other hand, zeolites are also recognized as drug delivery systems (DDS) carriers for numerous pharmacologically active agents. The enhanced bioactive ability of DDS zeolite as a drug carrying nanoplatform is confirmed, making this system more specific and efficient, compared to the drug itself. These two applications of zeolite, in fact, illustrate the importance of (ir)reversibility of the adsorption process. This review gives deep insight into the balance and dynamics that are established during that process, i.e., the interaction between zeolites and pharmaceuticals, helping scientists to expand their knowledge necessarily for a more effective application of the adsorption phenomenon of zeolites.

Near-Infrared Spectrum of the First Excited State of Au2.

Au2 + is a simple but crucial model system for understanding the diverse catalytic activity of gold. While the Au2 + ground state (X2Σg +) is understood reasonably well from mass spectrometry and computations, no spectroscopic information is available for its first excited state (A2Σu +). Herein, we present the vibrationally resolved electronic spectrum of this state for cold Ar‐tagged Au2 + cations. This exceptionally low‐lying and well isolated A2Σ(u) +←X2Σ(g) + transition occurs in the near‐infrared range. The observed band origin (5738 cm−1, 1742.9 nm, 0.711 eV) and harmonic Au−Au and Au−Ar stretch frequencies (201 and 133 cm−1) agree surprisingly well with those predicted by standard time‐dependent density functional theory calculations. The linearly bonded Ar tag has little impact on either the geometric or electronic structure of Au2 +, because the Au2 +⋅⋅⋅Ar bond (∼0.4 eV) is much weaker than the Au−Au bond (∼2 eV). As a result of 6 s←5d excitation of an electron from the antibonding σu * orbital (HOMO‐1) into the bonding σg orbital (SOMO), the Au−Au bond contracts substantially (by 0.1 Å).

Hydrogen peroxide decomposition into oxygen in different soils: Kinetic analysis, mechanism and implication in catalyzed hydrogen peroxide propagations

Rapid hydrogen peroxide (H2O2) decomposition in soils is one of the most important barriers standing in front of catalyzed H2O2 propagations (CHP) for soil and groundwater remediation, and the rates depend greatly on soil components. However, there are lack of indicators to quantitatively evaluate the processes in various soils. Different from previous studies focusing on H2O2 decomposition, O2 production kinetics are more valuable due to the direct relationship with H2O2 utilization. In this contribution, O2 production during H2O2 decomposition in the soil slurry was in situ detected using a fiber-optic oxygen transmitter. A kinetic model of O2 production was developed, which can be fitted well by the measured data of 18 soil samples. A kinetic constant on O2 production (kO2) ranging from 0.001 min−1 to 0.057 min−1 was obtained from the model, which represents the diverse catalytic activity of the soils. The constant kO2 is correlated with the contents of manganese, iron as well as inorganic carbon in the soils, and Mn mineral is the dominant factor. Three types of soils were selected to investigate the effect of acid-washing and stabilizer phosphate addition on phenol oxidation in CHP. Acid-washing can greatly suppress O2 production, while phosphate addition is not desirable for the highly active soils. Phenol slightly inhibits O2 production in the soils with higher kO2 values, which are inverse with those of phenol degradation. Acid-washing can remove Mn minerals but retain most of Fe components, and accordingly increase phenol degradation. Both hydroxyl radicals and superoxide radicals contribute to phenol degradation, and the latter ones display a more significant role. This work increases the understanding of the mechanism of H2O2 decomposition in the soils and provides a parameter (kO2) to guide CHP technologies in soil remediation.

Cyclometalated Half-Sandwich Iridium(III) Complexes: Synthesis, Structure, and Diverse Catalytic Activity in Imine Synthesis Using Air as the Oxidant.

Four air-stable cyclometalated half-sandwich iridium complexes 1-4 with C,N-donor Schiff base ligands were prepared through C-H activation in moderate-to-good yields. These complexes have been well characterized, and their exact structure was elaborated on by single-crystal X-ray analysis. The iridium(III) complexes 1-4 showed good catalytic activity in the imine synthesis under open-flask conditions (air as the oxidant) from primary amine oxidative homocoupling, secondary amine dehydrogenation, and the cross-coupling reaction of amine and alcohol. Substituents bonded on the ligands of the iridium complexes displayed little effect on the catalytic efficiency. The stability and good catalytic efficiency of the iridium catalysts, mild reaction conditions, and substrate universality showed their potential application in industrial production.

Quantifying evolving toxicity in the TAML/peroxide mineralization of propranolol.

SummaryOxidative water purification of micropollutants (MPs) can proceed via toxic intermediates calling for procedures for connecting degrading chemical mixtures to evolving toxicity. Herein, we introduce a method for projecting evolving toxicity onto composite changing pollutant and intermediate concentrations illustrated through the TAML/H2O2 mineralization of the common drug and MP, propranolol. The approach consists of identifying the key intermediates along the decomposition pathway (UPLC/GCMS/NMR/UV-Vis), determining for each by simulation and experiment the rate constants for both catalytic and noncatalytic oxidations and converting the resulting predicted concentration versus time profiles to evolving composite toxicity exemplified using zebrafish lethality data. For propranolol, toxicity grows substantially from the outset, even after propranolol is undetectable, echoing that intermediate chemical and toxicity behaviors are key elements of the environmental safety of MP degradation processes. As TAML/H2O2 mimics mechanistically the main steps of peroxidase catalytic cycles, the findings may be relevant to propranolol degradation in environmental waters.

Half-Sandwich Iridium Complexes for the One-Pot Synthesis of Amides: Preparation, Structure, and Diverse Catalytic Activity.

Several types of air-stable N,O-coordinate half-sandwich iridium complexes containing Schiff base ligands with the general formula [Cp*IrClL] were synthesized in good yields. These stable iridium complexes displayed a good catalytic efficiency in amide synthesis. A variety of amides with different substituents were obtained in a one-pot procedure with excellent yields and high selectivities through the amidation of aldehydes with NH2OH·HCl and nitrile hydration under the catalysis of complexes 1-4. The excellent and diverse catalytic activity, mild conditions, broad substance scope, and environmentally friendly solvent make this system potentially applicable in industrial production. Half-sandwich iridium complexes 1-4 were characterized by NMR, elemental analysis, and IR techniques. Molecular structures of complexes 2 and 3 were confirmed by single-crystal X-ray analysis.

Half-Sandwich Ru(II) Complexes with N,O-Chelate Ligands: Diverse Catalytic Activity for Amine Synthesis in Water

Several types of β-ketoamino based N,O-coordinate half-sandwich ruthenium complexes have been synthesized in moderate to good yields. The stable ruthenium complexes displayed good and diverse catal...

Half-Sandwich Ruthenium Complexes for One-Pot Synthesis of Quinolines and Tetrahydroquinolines: Diverse Catalytic Activity in the Coupled Cyclization and Hydrogenation Process.

Four types of half-sandwich ruthenium complexes with an N,O-coordinate mode based on hydroxyindanone-imine ligands have been prepared in good yields. These stable ruthenium complexes exhibited high activity in the catalytic synthesis of quinolines from the reactions of amino alcohols with different types of ketones or secondary alcohols under very mild conditions. Moreover, the methodology for the direct one-pot synthesis of tetrahydroquinoline derivatives from amino alcohols and ketones has been also developed on the basis of the continuous catalytic activity of this ruthenium catalyst in the selective hydrogenation of the obtained quinoline derivatives with a low catalyst loading. The corresponding products, quinolines and tetrahydroquinoline derivatives, were afforded in good to excellent yields. The efficient and diverse catalytic activity of these ruthenium complexes suggested their potential large-scale application. All of the ruthenium complexes were characterized by various spectroscopies to confirm their structures.

Air-Stable Half-Sandwich Iridium Complexes as Aerobic Oxidation Catalysts for Imine Synthesis.

Several N,O-coordinate half-sandwich iridium complexes, 1-5, containing constrained bulky β-enaminoketonato ligands were prepared and clearly characterized. Single-crystal X-ray diffraction characterization of these complexes indicates that the iridium center adopts a distorted octahedral geometry. Complexes 1-5 showed good catalytic efficiency in the oxidative homocoupling of primary amines, dehydrogenation of secondary amines, and the oxidative cross-coupling of amines and alcohols, which furnished various types of imines in good yields and high selectivities using O2 as an oxidant under mild conditions. No distinctive substituent effects of the iridium catalysts were observed in these reactions. The diverse catalytic activity, broad substrate scope, mild reaction conditions, and high yields of the products made this catalytic system attractive in industrial processes.

Change in the dynamics of the catalytic action of azathioprine on the electroreduction process of Bi(III) ions under the influence of surfactants in the context of controlled drug release

The influence of mixed adsorption layers of azathioprine – Tween 80 as well as azathioprine – Triton X-100 on the multi-step process of Bi(III) electroreduction in chlorates(VII) was studied using EIS and other electrochemical methods. It has been shown that there is control of multistage process of electroreduction of Bi(III) ions through the chemical reaction of the formation of Bi - AZA active complexes on the electrode surface, which mediate electron transfer. Active complexes are a substrate in the process of electroreduction and their different structure and properties are the reason for the diverse catalytic activity of azathioprine. On the other hand, the Bi(III) ions electroreduction process becomes slower in the presence of mixed adsorption layers, because the surfactant molecules block the electrode surface.

A Precursor Approach for the Development of Lace-like Fe2O3 Nanocrystallites Triggered by Pressure Dependent Nucleation and Growth of Akaganeite over Clay Based Composites for Toluene Combustion

Embedded catalysts for toluene combustion, featuring iron oxide (FeOx) moieties on the surface of clay derived porous heterostructural supports (PCH) were developed. The nucleation and growth of Fe4Cl0.44O3.56(OH)4.44(H2O)0.2 (akaganeite) in the function of Fe precursor interaction with the support entailed creation of nanostructured Fe oxides on the PCH surface. The hydrothermal forcing of ions migration and thermal transformation of as-synthesized Fe-PCH altered the surface composition and crystallinity of the formed nanostructured Fe oxides, thereby affecting the advantageous effects of donation gauged by electronic transfer. The polymorphism of Fe oxides created on PCH supports resulted in diverse catalytic activity of toluene combustion. Analysis of XPS Fe 2p core excitations showed that elongation of crystallization time of iron moieties on as synthesized Fe-PCH, as well as shortening of the annealing time, led to highly oxidized Fe species, mainly in the form of an α-Fe2O3 phase. Pressure dependent...

Development of elementorganic chemistry in Belarus: historical flashback, modern status and perspectives (To the 100th anniversary of the birth of Yu. A. Ol’dekop)

The development of organometallic chemistry of metallocenes, in particular, the chemistry of organic derivatives of iron, manganese, titanium and niobium, is explained by their diverse catalytic activity with respect to polymerization reactions, isomerization and hydrogenation of olefins, cyclotrimerization of acetylene hydrocarbons, fixation of molecular nitrogen under mild conditions and many other processes, using these compounds as additives to fuels and high-temperature lubrication oils, vulcanization accelerators of rubbers constituting lacos and water-repellent impregnation, anti-knock agents, driers, fungicides, etc. Of particular interest are the synthetic methods and chemical transformations of titanocene and niobocene derivatives containing the metal-carbon σ -bond. Most of the titanium-c-derivatives have low thermal stability, and the niobocene derivatives are extremely sensitive to the action of air oxygen, which makes it difficult to study their chemical transformations. Carborane derivatives are used for the preparation of various types of polymers used in solid rocket fuels and as heat-resistant coatings. They are also used as agents in boroneutron capture therapy of oncological diseases. This review presents a brief historical flashback, the current state and further development of the work carried out in the laboratory of organoelement compounds, which began and was supervised by Yu. A. Ol’dekop, covering the period from 1971 to 2018. References include 80 references.

Biomimetic catalytic activity and structural diversity of cobalt complexes with N3O-donor Schiff base ligand

This report describes the syntheses and structural characterizations of four new cobalt(III) compounds (1–4) derived from a tetradentate Schiff base ligand and their catalytic oxidation of different o-aminophenols in aerobic condition. X-ray crystal structural studies reveal that both pseudohalide ions and solvents used for the syntheses have significant influence on the structural diversity in these systems. All these compounds show the diverse catalytic activity towards the aerial oxidation of different o-aminophenols. As expected, the substitutionally labile coordination sites available for substrate binding is responsible for significantly higher catalytic activity of 1 and 2 then others. Literature reports reveal that although significant attention has been made to the catalytic oxidation of some substituted o-aminophenols in terms of the isolations and characterizations of their oxidised products with the native enzyme and its models, but the detailed kinetic studies were not available in the literature. Herein, we have examined the detailed kinetic studies of the aerobic oxidation of two substituted o-aminophenols, namely 2-amino-5-methylphenol and 2-amino-4-methylphenol, using 1 and 2 as catalysts. ESI mass spectrometry provides significant information to get insight into the mechanistic details and further disclose that the methyl substation in aromatic ring does not inhibit formation of the complex-substrate aggregate but it resulted the phenoxazine chromophore instead of phenoxazinone chormophore.

Fabrication and Diverse Ring-Expansion Nanocatalysis of Functionalized Pt-Nanoparticles to a General Synthesis of Pyrrolines: A 3D-Mid-IR Study

An unprecedented nanofabrication of functionalized Pt-NPs under mild conditions was accomplished through oxidative insertion of PtBr2 into the O–C bond of ArCH(OMe)2. TEM and SEM imaging, EELS, XPS, and ESI–MS analyses found the NPs possessing the molecular formula Br2(MeO)PtIVCH(OMe)Ph and low-dimensional spherical morphology. Ketone and amide functionality-bearing electrophilic cyclopropanes underwent ring-opening cyclization. Size-dependent catalytic activity of the NPs was investigated using stabilizers and newly introduced PhCH(OMe)2 during the synthesis of 2-pyrrolines. The organometallic-NPs were effective for cyclopropane ring-expansion using propargyl amine to 1-pyrrolines with depropargylation. Interestingly, the diverse catalytic activity of the Pt-NPs was effective for sp3C–H activated dual cyclization for the direct synthesis of fused-pyrrolo[3,2-c]pyridones. The possible reaction pathway was investigated by 3D-mid-IR-ATR, control experiments, and ESI–MS analyses. The NPs were superior in ter...

Phosphodiesterase Diversity and Signal Processing Within cAMP Signaling Networks.

A large number of neuromodulators activate G-protein coupled receptors (GPCRs) and mediate their cellular actions via the regulation of intracellular cAMP, the small highly diffusible second messenger. In fact, in the same neuron several different GPCRs can regulate cAMP with seemingly identical timecourses that give rise to distinct signaling outcomes, suggesting that cAMP does not have equivalent access to all its downstream effectors and may exist within defined intracellular pools or domains. cAMP compartmentalization is the process that allows the neuron to differentially interpret these various intracellular cAMP signals into cellular response. The molecular mechanisms that give rise to cAMP compartmentalization are not fully understood, but it is thought that phosphodiesterases (PDEs), the enzymes that degrade cAMP, significantly contribute to this process. PDEs, as the sole mechanism of signal termination for cAMP, hold great promise as therapeutic targets for pathologies that are due to the dysregulation of intracellular cAMP signaling. Due to their diverse catalytic activity, regulation and localization each PDE subtype expressed in a given neuron may have a distinct role on downstream signaling.

Tuning the geometry and biomimetic catalytic activity of manganese(III)-tetrabromocatecholate based robust platforms by introducing substitution at pyridine

The present report describes synthesis, characterization, crystal structures and catecholase activity of a series of five new manganese(III) complexes (1–5) derived from redox-noninnocent tetrabromocatecholate ligand in combination with different substituted pyridines. X-ray crystallography reveals that the geometry of manganese(III) centers in 1 and 2 is square pyramidal and they are pseudo-dimeric in the solid state resulting from the weak bonding of manganese(III) with a catecholate oxygen atom from the adjacent manganese(III) unit together with other weak interactions like hydrogen bonding and π⋯π stacking interactions. On the other hand, complexes 3–5 are discrete octahedral structures. All the complexes exhibit strong catecholase activity and their diverse catalytic activity can nicely be explained by the nature of substitution at pyridine ring — better electron donor inhibits the reduction of the metal center thereby lowering catecholase activity and vice versa (1 and 2 vs. 3–5). Besides the donor property of ancillary ligands, the structural distortion has also significant role in the biomimetic catalytic activity (1 vs. 2).

Scope and selectivity of B(C6F5)3-catalyzed reactions of the disilane (Ph2SiH)2

The diverse catalytic activity of the electrophilic borane B(C6F5)3 in reactions of silanes with organic substrates has been exploited extensively in studies that mostly focus on very particular, useful functional group transformations in organic synthesis. This study examines the potential for harnessing the collective, broad scope of these transformations in the preparation of new oligosilane derivatives. Borane-catalyzed hydrosilation, heterodehydrogenative coupling, and dealkylative coupling reactions of a wide range of substrates with the disilane (Ph2SiH)2 were investigated. These allowed new mono- and disubstituted disilanes to be prepared that contain SiO, SiS, and SiC linkages. Challenges and opportunities are described that arise from competing “over-reduction” chemistry, and the sensitivity of the catalysis to both the Lewis basicity and steric bulk of the substrates is examined.

Valence tautomerism induced nucleophilic ipso substitution in a coordinated tetrabromocatecholate ligand and diverse catalytic activity mimicking the function of phenoxazinone synthase

Two new manganese(III) complexes, [pyH][Mn(Br4Cat)2(py)] (1) and [Mn(Br4Cat)(Br3pyCat)(py)2] (2), where py is pyridine, Br4CatH2 is tetrabromocatechol and Br3pyCatH2 is 3,5,6-tribromo-4-pyridiniumcatechol, derived from redox ‘noninnocent’ bromo-substituted catecholate ligands are reported. Both complexes were characterized by various spectroscopic techniques in addition to the single crystal X-ray crystallography, and the electrochemical behavior of these complexes was investigated by cyclic voltammetry. Variable temperature UV–vis spectral studies for complex 1 reveal an unprecedented observation in which a dramatic increase of the ligand-to-metal charge transfer band at 592nm associated with concomitant change in color of the solution from olive-green to dark-green is noticed with increase in temperature. This unprecedented spectral feature is consistent with the formation of a new species 2 in which valence tautomerism induced aromatic nucleophilic substitution of a tetrabromocatecholate ligand by pyridine is observed. DFT calculations have been used to rationalize this unexpected result. To the best of our knowledge, the nucleophilic aromatic substitution of tetrabromosemiquinone by pyridine to generate this pyridinium-containing catecholate ligand is the first example of valence tautomerism induced nucleophilic ipso substitution by a nitrogen containing ligand. Although the electrochemical behavior of both complexes is similar, the probable role of a positive charge on the ligand backbone has been discussed in order to justify the significantly higher catalytic activity of complex 2 over complex 1.

A new type of p-type NiO/n-type ZnO nano-heterojunctions with enhanced photocatalytic activity

A new type of NiO/ZnO nano-heterojunction was developed by the template-assisted approach. The p–n nano-heterojunctions were formed between the NiO and ZnO nanoparticles in the ultrathin shell of the NiO/ZnO hollow nanospheres. The grain size of the NiO/ZnO nano-heterojunctions is in the 10 nm scale, and the specific surface area is higher than 100 m2 g−1. Moreover, the ultrathin shell makes the distribution of the NiO/ZnO nano-heterojunctions to arrange in a single-layer structure rather than a stacking arrangement. Therefore, this new type of the NiO/ZnO nano-heterojunctions could almost completely separate the electron and hole to the surface rather than being wasted in the materials. As a result, the photocatalytic activity of the p-type NiO/n-type ZnO nano-heterojunctions for the degradation of rhodamine B (RhB) was much higher than that of ZnO. In particular, the p-type NiO/n-type ZnO hollow nanospheres with different Ni/Zn molar ratios exhibited diverse catalytic activity, the mechanism of which has been discussed in detail.