Category Archives: ChemistryOpen

Design of Promising Uranyl(VI) Complexes Thin Films with Potential Applications in Molecular Electronics

Posted on 5 January 2024 by

Oxo uranyl(VI) complexes were successfully synthesized, characterized and deposited by thermal evaporation and optical and electrical features of films were examined. The bandgap for the films is in the Interval of 2.39 and 2.79 eV and the films present ohmic electrical behavior, with maximum current values of order of 10⁻³ A. These uranyl films can be used in Molecular Electronics applications.

Abstract

In this work, it is proposed the development of organic semiconductors (OS) based on uranyl(VI) complexes. The above by means of the synthesis and the characterization of the complexes by Infrared spectroscopy, Nuclear magnetic resonance spectroscopy, mass spectrometry, and X-ray diffraction. Films of these complexes were deposited and subsequently, topographic and structural characterization was carried out by Scanning Electron Microscopy, X-ray diffraction, and Atomic Force Microscopy. Additionally, the nanomechanical evaluation was performed to know the stiffness of uranyl films using their modulus of elasticity. Also, the optical characterization took place in the devices and their bandgap value ranges between 2.40 and 2.93 eV being the minor for the film of the uranyl complex with the N on pyridine in position 4 (2 c). Finally, the electrical behavior of the uranyl(VI) films was evaluated, and important differences were obtained: the uranyl complex with the N on pyridine in position 2 (2 a) film is not influenced by changes in lighting and its current density is in the order of 10⁻³ A/cm². The film with uranyl complex with the N on pyridine in position 3 (2 b) and 2 c presents a greater current flow under lighting conditions and two orders of magnitude larger than in film 2 a. In these films 2 b and 2 c, ohmic behavior occurs at low voltages, while at high voltages the charge transport changes to space-charge limited current behavior.

Photocatalytic Degradation of Malachite Green by Titanium Dioxide/Covalent Organic Framework Composite: Characterization, Performance and Mechanism

Posted on 5 January 2024 by nDongmei Yao, nXiaoting Xie, nXuling Liang, nSufen Lu, nHongfang Lain

In this paper, a titanium dioxide/covalent organic framework (TiO₂/COF) composite was prepared and its photocatalytic removal of dye was investigated. Using tetrabutyl titanate as a titanium source, TiO₂ nanomaterial was prepared by sol-gel method. In the presence of TiO₂, TiO₂/COF core-shell composite was prepared by solvothermal synthesis using melamine and 1,4-phthalaldehyde as ligands. The prepared materials are characterized by SEM, TEM, XPS, XRD, TG, FTIR, BET, EPR, PL, and UV-Vis-DRS techniques. Using malachite green (MG) as a model of dye wastewater, the photocatalytic degradation performance of TiO₂/COF composites was investigated under the irradiation of ultraviolet light. The results show that the modification of COF significantly improves the photocatalytic efficiency of TiO₂, the degradation rate increases from 69.77 % to 93.64 %, and the reaction rate constant of the first-order kinetic equation is increased from 0.0078 min⁻¹ to 0.0192 min⁻¹. Based on the free radical capture experiment, the photocatalytic degradation mechanism of TiO₂/COF was discussed, and the feasibility of its photocatalytic degradation of malachite green was theoretically clarified. Accordingly, a simple and practical method for photocatalytic degradation of malachite green was constructed, which has potential application value in the degradation of dye wastewater.

Abstract

In this paper, a titanium dioxide/covalent organic framework (TiO₂/COF) composite was prepared and its photocatalytic removal of dye was investigated. Using tetrabutyl titanate as a titanium source, TiO₂ nanomaterial was prepared by sol-gel method. In the presence of TiO₂, TiO₂/COF core-shell composite was prepared by solvothermal synthesis using melamine and 1,4-phthalaldehyde as ligands. The prepared materials are characterized by SEM, TEM, XPS, XRD, TG, FTIR, BET, EPR, PL, and UV-Vis-DRS techniques. Using malachite green as a model of dye wastewater, the photocatalytic degradation performance of TiO₂/COF composites was investigated under the irradiation of ultraviolet light. The results show that the modification of COF significantly improves the photocatalytic efficiency of TiO₂, the degradation rate increases from 69.77 % to 93.64 %, and the reaction rate constant of the first-order kinetic equation is increased from 0.0078 min⁻¹ to 0.0192 min⁻¹. Based on the free radical capture experiment, the photocatalytic degradation mechanism of TiO₂/COF was discussed, and the feasibility of its photocatalytic degradation of malachite green was theoretically clarified. Accordingly, a simple and practical method for photocatalytic degradation of malachite green was constructed, which has potential application value in the degradation of dye wastewater.

CYTOP® 366: A Tertiary Phosphine Inaccessible by Most Traditional Hydrophosphination Methods

Posted on 3 January 2024 by

Traditional radical-catalyzed methods to prepare alkylphosphines are not suitable for the target molecule, tricyclohexylphosphine, otherwise known as CYTOP® 366. Through computational study, we explore why this tertiary phosphine is inaccessible via a radical-catalyzed addition and describe an alternative pathway to our target, which not only achieves good yield and purity but is also a safe and workable route for industrial scale manufacture.

Abstract

Homogenous catalysis is an essential tool within the commercial manufacture of bulk and fine chemicals. Within this, phosphine ligands, such as tricyclohexylphosphine, otherwise known as CYTOP® 366, are a crucial component. When designing a pathway to your ligand of choice, some key considerations include safety, yield and quality, but at commercial volumes we must also balance cost and consider the technologies readily available. Herein, we report the synthetic route that was chosen to manufacture tricyclohexylphosphine at commercial scale. We also consider, with the use of computational calculations, why traditional hydrophosphination methods failed, where the selected pathway succeeded.

Unraveling Reactivity Pathways: Dihydrogen Activation and Hydrogenation of Multiple Bonds by Pyramidalized Boron‐Based Frustrated Lewis Pairs

Posted on 20 December 2023 by nHimangshu Mondal, nPratim Kumar Chattarajn

A DFT-based study explores the H₂ activation by pyramidalized boron-based B/E-FLP (E=N, P, As, Sb and Bi, etc.) systems. The study also highlights the hydrogenation process of multiple bonds with the help of B/N-FLP.

Abstract

The activation of H₂ by pyramidalized boron-based frustrated Lewis Pairs (FLPs) (B/E-FLP systems where “E” refers to N, P, As, Sb, and Bi) have been explored using density functional theory (DFT) based computational study. The activation pathway for the entire process is accurately characterized through the utilization of the activation strain model (ASM) of reactivity, shedding light on the underlying physical factors governing the process. The study also explores the hydrogenation process of multiple bonds with the help of B/N-FLP. The research findings demonstrate that the liberation of activated dihydrogen occurs in a synchronized, albeit noticeably asynchronous, fashion. The transformation is extensively elucidated using the activation strain model and the energy decomposition analysis. This approach suggests a co-operative double hydrogen-transfer mechanism, where the B−H hydride triggers a nucleophilic attack on the carbon atom of the multiple bonds, succeeded by the migration of the protic N−H.

Enhanced Photocatalytic H2 Generation by Light‐Induced Carbon Modification of TiO2 Nanotubes

Posted on 13 December 2023 by

A closer examination of the role and impact of carbon within TiO₂ nanotubes on H₂ evolution and photoelectrochemical performance was carried out. Carbon is inherently present in nanotubes as remnant organic electrolyte used in the anodization processes. This residue serves as a carbon source during annealing in air, and when exposed to UV light, the carbon undergoes modification, thus resulting in enhanced photocatalytic efficiency.

Abstract

Titanium dioxide (TiO₂) is the material of choice for photocatalytic and electrochemical applications owing to its outstanding physicochemical properties. However, its wide bandgap and relatively low conductivity limit its practical application. Modifying TiO₂ with carbon species is a promising route to overcome these intrinsic complexities. In this work, we propose a facile method to modify TiO₂ nanotubes (NTs) based on the remnant organic electrolyte retained inside the nanotubes after the anodization process, that is, without removing it by immersion in ethanol. Carbon-modified TiO₂ NTs (C-TiO₂ NTs) showed enhanced H₂ evolution in photocatalysis under UV illumination in aqueous solutions. When the C-TiO₂ NTs were subjected to UV light illumination, the carbon underwent modification, resulting in higher measured photocurrents in the tube layers. After UV illumination, the IPCE of the C-TiO₂ NTs was 4.4-fold higher than that of the carbon-free TiO₂ NTs.

In situ Investigations of the Formation Mechanism of Metastable γ‐BiPd Nanoparticles in Polyol Reductions

Posted on 13 December 2023 by

The formation of γ-BiPd in a polyol process has been monitored by X-ray powder diffraction, light scattering, and in situ measurements of redox potential and pH value. Palladium nanoparticles are formed as primary reaction product followed by a successive reduction of bismuth cations and a diffusion-controlled formation of the intermetallic target phase.

Abstract

Synthesizing intermetallic phases containing noble metals often poses a challenge as the melting points of noble metals often exceed the boiling point of bismuth (1560 °C). Reactions in the solid state generally circumvent this issue but are extremely time consuming. A convenient method to overcome these obstacles is the co-reduction of metal salts in polyols, which can be performed within hours at moderate temperatures and even allows access to metastable phases. However, little attention has been paid to the formation mechanisms of intermetallic particles in polyol reductions. Identifying crucial reaction parameters and finding patterns are key factors to enable targeted syntheses and product design. Here, we chose metastable γ-BiPd as an example to investigate the formation mechanism from mixtures of metal salts in ethylene glycol and to determine critical factors for phase formation. The reaction was also monitored by in situ X-ray diffraction using synchrotron radiation. Products, intermediates and solutions were characterized by (in situ) X-ray diffraction, electron microscopy, and UV-Vis spectroscopy. In the first step of the reaction, elemental palladium precipitates. Increasing temperature induces the reduction of bismuth cations and the subsequent rapid incorporation of bismuth into the palladium cores, yielding the γ-BiPd phase.

Secondary 3‐Chloropiperidines: Powerful Alkylating Agents

Posted on 13 December 2023 by

The synthesis of secondary 3-chloropiperidines and highly strained bicyclic aziridines is reported, including a new method for the selective mono-chlorination of unsaturated primary amines. The novel compounds, which closely resemble natural alkylating agents, proved to be more active than previously reported 3-chloropiperidines in a DNA cleavage assay, highlighting their potential as powerful alkylating agents.

Abstract

In previous works, we demonstrated that tertiary 3-chloropiperidines are potent chemotherapeutics, alkylating the DNA through the formation of bicyclic aziridinium ions. Herein, we report the synthesis of novel secondary 3-chloropiperidine analogues. The synthesis incorporates a new procedure to monochlorinate unsaturated primary amines utilizing N-chlorosuccinimide, while carefully monitoring the temperature to prevent dichlorination. Furthermore, we successfully isolated highly strained bicyclic aziridines by treating the secondary 3-chloropiperidines with a sufficient amount of base. We conclude this work with a DNA cleavage assay as a proof of principle, comparing our previously known substrates to the novel compounds. In this, the secondary 3-chloropiperidine as well as the isolated bicyclic aziridine, proved to be more effective than their tertiary counterpart.

Hydrogen Production via Methane Decomposition over Alumina Doped with Titanium Oxide‐Supported Iron Catalyst for Various Calcination Temperatures

Posted on 12 December 2023 by

Iron metal was used for hydrogen production via methane decomposition using alumina as support; furthermore, to overcome the drawback of alumina, titanium dioxide was added at 20 %, considering various calcination temperatures. The results show that adding 20 % of TiO₂ to alumina enhances the activity of catalysts for hydrogen production and stability. Carbon was produced as carbon nanotubes (CNT).

Abstract

The decomposition of methane has been chosen as an alternative method for producing hydrogen. In this study, 20 % Fe was used as the active metal part of the catalyst. To better comprehend the impact of the supporting catalytic properties, alumina and titania-alumina composite were investigated as supports. Iron-based catalysts were prepared by impregnation method and then calcined at different temperatures (300 °C, 500 °C, and 800 °C). The catalysts were examined at 800 °C under atmospheric pressure with a 15 mL/min total flow rate and 2 : 1 CH₄ to N₂ feed ratio. The textural and morphological characteristics of the fresh calcined and spent catalysts were investigated. The catalytic activity and stability data demonstrated that Fe supported over TiO₂-Al₂O₃ calcined at 500 °C performed the best of all evaluated catalysts with a more than 80 % hydrogen yield. The Raman spectra result showed that graphitic carbon was produced for all used titanium dioxide catalysts. Moreover, according to transmission electron microscopy (TEM) results, the carbon deposited on the catalysts’ surface is carbon nanotubes (CNT).

Identifying Phosphodiesterase‐5 Inhibitors with Drug Repurposing Approach: Implications in Vasodysfunctional Disorders

Posted on 7 December 2023 by

Phosphodiesterase type 5 plays a crucial role in regulating key signaling molecules involved in various physiological processes. This study combines virtual screening and molecular dynamics simulations to investigate the repurposing of FDA-approved drugs as potential PDE5 inhibitors.

Abstract

Phosphodiesterase type 5 (PDE5) is a multidomain protein that plays a crucial role in regulating cellular cyclic guanosine monophosphate (cGMP), a key signaling molecule involved in various physiological processes. Dysregulation of PDE5 and cGMP signaling is associated with a range of vasodysfunctional disorders, necessitating the development of effective therapeutic interventions. This study adopts comprehensive approach, combining virtual screening and molecular dynamics (MD) simulations, to repurpose FDA-approved drugs as potential PDE5 inhibitors. The initial focus involves selecting compounds based on their binding affinity. Shortlisted compounds undergo a meticulous analysis for their drug profiling and biological significance, followed by the activity evaluation and interaction analysis. Notably, based on binding potential and drug profiling, two molecules, Dutasteride and Spironolactone, demonstrate strong potential as PDE5 inhibitors. Furthermore, all atom MD simulations were employed (500 ns) to explore dynamic behavior of Dutasteride and Spironolactone in complexes with PDE5. Principal components analysis (PCA) and free energy landscape (FEL) analyses are further leveraged to decipher that the binding of Dutasteride and Spironolactone stabilizes the structure of PDE5 with minimal conformational changes. In summary, Dutasteride and Spironolactone exhibit remarkable affinity for PDE5 and possess characteristics that suggest their potential as therapeutic agents for conditions associated with PDE5 dysfunction.

Surface Modification of Lignite with Alkyl and Mixed Alkyl‐Aryl Films Generated from an Aryl Diazonium Salt and Alkyl Halides: Experimental Results and Theoretical Analyses

Posted on 5 December 2023 by

The surface of lignite has been modified with alkylcarboxylic moieties derived from alkyl halides by diverting the reactivity of the sterically hindered aryl radical obtained by reduction of the 2,6-dimethylbenzene diazonium tetrafluoroborate after its chemical reduction. Mixed alkyl-aryl layers are prepared by using 4-nitro or 3,5-bis-trifluoro benzenediazonium salts.

Abstract

In search of new possible uses of cheap lignite from the Kosova Bassin, the surface of lignite powders is modified with alkyl or mixed alkyl-aryl layers. Modification is performed in aqueous acid solution containing an aryl diazonium salt and an alkyl halide compound in millimolar concentration, in the presence of potassium iodide as a reducing agent at equimolar concentration. Attachment of alkyl films substituted with carboxylic groups and aryl films with nitro or bis-trifluoromethyl groups is characterized by IRATR and XPS spectroscopy. The formation of a stable interface during the grafting reactions of alkyl and aryl moieties with lignite surface has been confirmed by theoretical calculations. Aryl diazonium salts once chemically or spontaneously reduced are a source of aryl radicals, able to attach chemically to the material surface or to react with alkyl halides by abstracting the halogen atom. If the aryl diazonium salts are unable to graft to the coal surface due to steric hindrance, they can, nevertheless, abstract an iodine or bromine atom to generate alkyl radicals that react with the material surface.